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Peer-reviewed articles

2015

Moezzi,A. M., Fonn,D., Varikooty,J., Simpson,T. L. Overnight corneal swelling with high and low powered silicone hydrogel lenses. Journal of Optometry 2015;8,1:19-26. [ Show Abstract ]

Purpose To compare central corneal swelling after eight hours of sleep in eyes wearing four different silicone hydrogel lenses with three different powers. Methods Twenty-nine neophyte subjects wore lotrafilcon A (Dk, 140), balafilcon A (Dk, 91), galyfilcon A (Dk, 60) and senofilcon A (Dk, 103) lenses in powers -3.00, -10.00 and +6.00 D on separate nights, in random order, and on one eye only. The contra-lateral eye (no lens) served as the control. Central corneal thickness was measured using a digital optical pachometer before lens insertion and immediately after lens removal on waking. Results For the +6.00 D and -10.00 D, lotrafilcon A induced the least swelling and galyfilcon A the most. The +6.00 D power, averaged across lens materials, induced significantly greater central swelling than the -10.00 and -3.00 D (Re-ANOVA, p < 0.001), (7.7 ± 2.9% vs. 6.8 ± 2.8% and 6.5 ± 2.5% respectively) but there was no difference between -10.00 and -3.00 D. Averaged for power, lotrafilcon A induced the least (6.2 ± 2.8%) and galyfilcon A the most (7.6 ± 3.0%) swelling at the center (Re-ANOVA, p < 0.001). Central corneal swelling with +6.00 D was significantly greater than -10.00 D lens power despite similar levels of average lens transmissibility of these two lens powers. Conclusions The differences in corneal swelling of the lens wearing eyes are consistent with the differences in oxygen transmission of the silicone hydrogel lenses. In silicone hydrogel lenses central corneal swelling is mainly driven by central lens oxygen transmissibility.

Varikooty,J., Schulze,M. M., Dumbleton,K., Keir,N., Woods,C. A., Fonn,D., Jones,L. W. Clinical performance of three silicone hydrogel daily disposable lenses. Optometry and Vision Science 2015;92,3:301-311. [ Show Abstract ]

Purpose. To determine the clinical performance of DAILIES TOTAL1 (DT1), Clariti 1Day (C1D), and 1-DAY ACUVUE TruEye (AVTE) silicone hydrogel daily disposable contact lenses (SiHy DDCLs). Methods. Eligible participants, subdivided into asymptomatic and symptomatic groups, wore each SiHy DDCLs for three consecutive days. Each participant attended three visits (on day 1 at 0 hours; on days 1 and 3 after 8 hours ofwear) per lens type. The order of lens wear was randomized, with at least 1 day washout between lenses. Lens-related performance was evaluated by assessing lens surface deposits, wettability, pre-lens noninvasive tear breakup time, lens movement, and centration; ocular response assessments included conjunctival redness, corneal staining, and conjunctival staining and indentation. Results. Fifty-one asymptomatic and 53 symptomatic participantscompleted the study. For all visits, themeannoninvasive tear breakup timewas about 1 second longer withDT1 than withC1DandAVTE (p < 0.01).Overall, thewettability of all three lenses was good; however, DT1 was graded marginally better than the other lenses (both p < 0.01). On day 3, eyes wearing AVTE had significantly more dehydration-induced corneal staining compared with DT1 (AVTE, 24%; DT1, 11%; p < 0.01). After 8 hours, conjunctival staining was different between lenses (greatest with C1D and least with DT1; all p < 0.01). Conjunctival indentation was more prevalent with the C1D lenses (n = 70) compared with DT1 (n = 1; p < 0.01) and AVTE (n = 11; p < 0.01). Therewere no differences between asymptomatic and symptomatic lenswearers for any of the clinical parameters (all p 9 0.05). Conclusions. Each of the three SiHy DDCLs performed well. Noninvasive tear breakup time was longest and wettability was greater with DT1. C1D had the most conjunctival staining conjunctival indentation. There was no difference between asymptomatic and symptomatic wearers with regard to ocular response and contact lensYrelated parameters. These results suggest that SiHy DDCLs may be an excellent contact lens modality for the symptomatic patient.

2014

Gorbet,M., Peterson,R., McCanna,D., Woods,C., Jones,L., Fonn,D. Human corneal epithelial cell shedding and fluorescein staining in response to silicone hydrogel lenses and contact lens disinfecting solutions. Current eye research 2014;39,3:245-256. [ Show Abstract ]

Purpose: A pilot study was conducted to evaluate human corneal epithelial cell shedding in response to wearing a silicone hydrogel contact lens/solution combination inducing corneal staining. The nature of ex vivo collected cells staining with fluorescein was also examined. Methods: A contralateral eye study was conducted in which up to eight participants were unilaterally exposed to a multipurpose contact lens solution/silicone hydrogel lens combination previously shown to induce corneal staining (renu® fresh™ and balafilcon A; test eye), with the other eye using a combination of balafilcon A soaked in a hydrogen peroxide care system (Clear Care®; control eye). Lenses were worn for 2, 4 or 6 hours. Corneal staining was graded after lens removal. The Ocular Surface Cell Collection Apparatus was used to collect cells from the cornea and the contact lens. Results: In the test eye, maximum solution-induced corneal staining (SICS) was observed after 2 hours of lens wear (reducing significantly by 4 hours; p < 0.001). There were significantly more cells collected from the test eye after 4 hours of lens wear when compared to the control eye and the collection from the test eye after 2 hours (for both; n = 5; p < 0.001). The total cell yield at 4 hours was 813 ± 333 and 455 ± 218 for the test and control eyes, respectively (N = 5, triplicate, p = 0.003). A number of cells were observed to have taken up the fluorescein dye from the initial fluorescein instillation. Confocal microscopy of fluorescein-stained cells revealed that fluorescein was present throughout the cell cytoplasm and was retained in the cells for many hours after recovery from the corneal surface. Conclusion: This pilot study indicates that increased epithelial cell shedding was associated with a lens-solution combination which induces SICS. Our data provides insight into the transient nature of the SICS reaction and the nature of fluorescein staining observed in SICS. © 2014 Informa Healthcare USA, Inc.

Moezzi,A. M., Fonn,D., Varikooty,J., Simpson,T. L. Overnight corneal swelling with high and low powered silicone hydrogel lenses. Journal of Optometry 2014. [ Show Abstract ]

Purpose: To compare central corneal swelling after eight hours of sleep in eyes wearing four different silicone hydrogel lenses with three different powers. Methods: Twenty-nine neophyte subjects wore lotrafilcon A (Dk, 140), balafilcon A (Dk, 91), galyfilcon A (Dk, 60) and senofilcon A (Dk, 103) lenses in powers -3.00, -10.00 and +6.00 D on separate nights, in random order, and on one eye only. The contra-lateral eye (no lens) served as the control. Central corneal thickness was measured using a digital optical pachometer before lens insertion and immediately after lens removal on waking. Results: For the +6.00 D and -10.00 D, lotrafilcon A induced the least swelling and galyfilcon A the most. The +6.00 D power, averaged across lens materials, induced significantly greater central swelling than the -10.00 and -3.00 D (Re-ANOVA, p < 0.001), (7.7 ± 2.9% vs. 6.8 ± 2.8% and 6.5 ± 2.5% respectively) but there was no difference between -10.00 and -3.00 D. Averaged for power, lotrafilcon A induced the least (6.2 ± 2.8%) and galyfilcon A the most (7.6 ± 3.0%) swelling at the center (Re-ANOVA, p < 0.001). Central corneal swelling with +6.00 D was significantly greater than -10.00 D lens power despite similar levels of average lens transmissibility of these two lens powers. Conclusions: The differences in corneal swelling of the lens wearing eyes are consistent with the differences in oxygen transmission of the silicone hydrogel lenses. In silicone hydrogel lenses central corneal swelling is mainly driven by central lens oxygen transmissibility. © 2013 Spanish General Council of Optometry.

2013

Woods,J., Guthrie,S. E., Keir,N., Dillehay,S., Tyson,M., Griffin,R., Choh,V., Fonn,D., Jones,L., Irving,E. Inhibition of defocus-induced myopia in chickens. Investigative Ophthalmology and Visual Science 2013;54,4:2662-2668. [ Show Abstract ]

PURPOSE. To determine the effect of wearing a lens with a unique peripheral optical design on the development and progression of defocus-induced myopia in newly hatched chickens.METHODS. Eighty-five newly hatched chickens underwent bilateral retinoscopy and A-scan ultrasound to determine their refractive error and axial length. They were randomly divided into Control and two Test groups, in which each chicken was fitted with a goggle-lens over the right eye, with the left eye remaining untreated. The Control group wore a lens of power - 10.00 diopters (D) of standard spherical optical design. The two Test lenses both had a central optical power -10.00 D, but used different peripheral myopia progression control (MPC) designs. For all groups, retinoscopy was repeated on days 3, 7, 10, and 14; ultrasound was repeated on day 14.RESULTS. On day 0 there was no statistical difference in refractive error (mean +6.92 D) or axial length (mean 8.06 mm) between Test and Control groups or treated and untreated eyes (all P > 0.05). At day 14, 37 (43.5%) of 85 chickens had not experienced goggle detachment and were included in the final analyses. In this cohort there was a significant refractive difference between the treated eyes of the Control group (n = 17) and those of Test 1 (n = 14) and Test 2 (n = 6) groups (both P < 0.01): Control -4.65 ± 2.11 D, Test 1 +4.57 ± 3.11 D, Test 2 +1.08 ± 1.24 D (mean ± SEM). There was also a significant axial length difference (both P < 0.01): Control 10.55 ± 0.36 mm, Test 1 9.99 ± 0.14 mm, Test 2 10.17 ± 0.18 mm.CONCLUSIONS. Use of these unique MPC lens designs over 14 days caused a significant reduction in the development of defocus-induced myopia in chickens; the degree of reduction appeared to be design specific. © 2013 The Association for Research in Vision and Ophthalmology, Inc.

Dumbleton,K., Woods,C. A., Jones,L. W., Fonn,D. The impact of contemporary contact lenses on contact lens discontinuation. Eye and Contact Lens 2013;39,1:93-99. [ Show Abstract ]

OBJECTIVES: Discontinuation or "dropout" from contact lens (CL) wear continues to afflict the CL industry. This study was conducted to determine whether the advent of new CL materials and designs has impacted the dropout rate and the reasons for discontinuation. METHODS: Current and lapsed CL wearers residing in Canada were recruited using Facebook to take part in an on line survey investigating CL wearing experiences during 2008 to 2010 and to establish the percentage of participants who temporarily and permanently discontinued CL wear during the period surveyed. RESULTS: Four thousand two hundred seven eligible surveys were received (64% female; median age 27 years). Forty percent had lapsed from lens wear for at least 4 months; however, 62% of the lapsed wearers (LWs) resumed wear. There were no differences between LWs and nonlapsed wearers (NLWs) with respect to gender; however, LWs were older, started lens wear when older, and had not worn lenses for as long as NLWs (all P<0.001). More NLWs than LWs wore silicone hydrogel CLs (49% vs. 38%, P<0.001) and more LWs than NLWs wore daily disposable lenses and hydrogel CLs (24% vs. 19% and 22% vs. 18%, respectively, P=0.001). Primary reasons for discontinuation were discomfort (24%), dryness (20%), red eyes (7%), and expense (7%). Compliance with lens replacement was no different between LWs and NLWs (48% vs. 45%). CONCLUSIONS: About 23% of those surveyed had discontinued CL wear permanently. The primary reasons for dropping out continue to be discomfort and dryness. Dropout rates were lower in silicone hydrogel wearers. © 2013 Lippincott Williams & Wilkins.

Nichols,K. K., Redfern,R. L., Jacob,J. T., Nelson,J. D., Fonn,D., Forstot,S. L., Huang,J. -F, Holden,B. A., Nichols,J. J. The TFOS International Workshop on Contact Lens Discomfort: Report of the definition and classification subcommittee. Investigative Ophthalmology and Visual Science 2013;54,11:TFOS14-TFOS19.

Robinson,B., Feng,Y., Woods,C. A., Fonn,D., Gold,D., Gordon,K. Prevalence of visual impairment and uncorrected refractive error-report from a canadian urban population-based study. Ophthalmic epidemiology 2013;20,3:123-130. [ Show Abstract ]

Purpose: The prevalence of visual impairment due to uncorrected refractive error has not been previously studied in Canada. A population-based study was conducted in Brantford, Ontario. Methods: The target population included all people 40 years of age and older. Study participants were selected using a randomized sampling strategy based on postal codes. Presenting distance and near visual acuities were measured with habitual spectacle correction, if any, in place. Best corrected visual acuities were determined for all participants who had a presenting distance visual acuity of less than 20/25. Results: Population weighted prevalence of distance visual impairment (visual acuity <20/40 in the better eye) was 2.7% (n=768, 95% confidence interval (CI) 1.8-4.0%) with 71.8% correctable by refraction. Population weighted prevalence of near visual impairment (visual acuity <20/40 with both eyes) was 2.2% (95% CI 1.4-3.6) with 69.1% correctable by refraction. Multivariable adjusted analysis showed that the odds of having distance visual impairment was independently associated with increased age (odds ratio, OR, 3.56, 95% CI 1.22-10.35; 65 years compared to those 39-64 years), and time since last eye examination (OR 4.93, 95% CI 1.19-20.32; 5 years compared to 2 years). The same factors appear to be associated with increased prevalence of near visual impairment but were not statistically significant. Conclusions: The majority of visual impairment found in Brantford was due to uncorrected refractive error. Factors that increased the prevalence of visual impairment were the same for distance and near visual acuity measurements. © 2013 Informa Healthcare USA, Inc. All rights reserved: reproduction in whole or part not permitted.

Varikooty,J., Keir,N., Richter,D., Jones,L. W., Woods,C., Fonn,D. Comfort response of three silicone hydrogel daily disposable contact lenses. Optometry and Vision Science 2013;90,9:945-953. [ Show Abstract ]

PURPOSE: To evaluate subjective ocular comfort across the day with three silicone hydrogel daily disposables (SHDDs) in a group of adapted lens wearers. METHODS: Masked subjects (asymptomatic or symptomatic of end-of-day (EOD) dryness with habitual lenses) wore three SHDDs: DAILIES TOTAL1 (DT1), Clariti 1day (C1D), or 1-DAY ACUVUE TRUEYE (AVTE), each for 3 days. On day 2, wearing time (WT) and comfort ratings after insertion, at 4, 8, and 12 hours, and at EOD were recorded. Because not all subjects wore lenses for 12 hours, comfort was analyzed across the day (up to 8 hours, 8 to 12 hours), and a new variable ("cumulative comfort" [CC]) was calculated for EOD. RESULTS: One hundred four subjects completed the study (51 asymptomatic, 53 symptomatic). The two groups had different WTs (mean WT, 14.0 and 12.7 hours, respectively; p < 0.001). Ocular comfort was rated higher in the asymptomatic group throughout the day (p < 0.001). One hundred four subjects wore all three SHDDs for at least 8 hours, whereas 74 (45 asymptomatic, 29 symptomatic) subjects wore them for 12 hours or longer. Comfort ratings were higher with DT1 (least square means [LSM] = 91.0) than with C1D (LSM = 86.5; p < 0.001) and AVTE (LSM = 87.7; p = 0.011) for the first 8 hours and lower with C1D compared with DT1 (p = 0.012) from 8 to 12 hours. Mean EOD (± SD) comfort with the C1D lens was 72 ± 21, lower than both DT1 (mean, 79 ± 17; p = 0.001) and AVTE (mean, 78 ± 21; p = 0.010). Mean CC was higher in the asymptomatic group (mean, 1261 ± 59) compared with that in the symptomatic group (mean, 1009 ± 58; p < 0.001) and higher for DT1 (mean, 1184 ± 258) than C1D (mean, 1094 ± 318; p = 0.002) and AVTE (mean, 1122 ± 297; p = 0.046). CONCLUSIONS: All three SHDDs had average WTs of 12 hours or longer for 1 day. Comfort during the first 12 hours was highest with DT1 (similar to AVTE between 8 and 12 hours) and lowest with C1D. End-of-day comfort was lowest with C1D, and CC was highest for DT1. Cumulative comfort may be a valuable new metric to assess ocular comfort during the day. © 2013 American Academy of Optometry.

2012

Woods,J., Jones,L., Woods,C., Schneider,S., Fonn,D. Use of a photographic manipulation tool to assess corneal vascular response. Optometry and Vision Science 2012;89,2:215-220. [ Show Abstract ]

Purpose. Corneal vasculature change in contact lens wearers has been linked to the level of hypoxia within the cornea. To assess the impact a treatment has on limbal vessels, a sensitive method of measurement and quantification is required. Methods. A group of 21 highly myopic, hydrogel wearers, with preexisting signs of corneal hypoxia, were enrolled into a study where they wore sifilcon A silicone hydrogel lenses (Dk/t = 117), on a daily wear basis for 9 months. At all scheduled visits, photographs were taken of the superior, inferior, temporal, and nasal limbal regions which were then imported into Adobe Photoshop. A red-free filter was applied to enhance the contrast of the blood columns. In each quadrant, the length of the longest visible blood column was measured and the blood columns that penetrated -0.5 mm into the cornea were counted. A control group of 11 non-lens wearers was recruited. Their photographs were taken at the beginning of the study and 9 months later. An independent, masked observer assessed the photographs. Results. There was a significant decrease in the maximum penetration of the blood column in all quadrants (p + 0.001) from baseline to the 9-month visit (e.g., superior: baseline 0.84 ± 0.39 mm; 9 months 0.63 ± 0.20 mm). There was also significant reduction in the number of visible blood columns longer than 0.5 mm in each quadrant (p + 0.001) from baseline to 9 months in all quadrants (e.g., superior: baseline 14.0 ± 8.2; 9 months 6.5 ± 6.0). The control group showed no change over time for the maximum blood column length (p = 0.638) or the number of columns >0.5 mm (p = 0.341). Conclusions. A group of highly myopic subjects exhibited reduction in the maximum length and number of blood columns in the cornea when refit with a highly permeable silicone hydrogel material. The use of photography, along with Adobe Photoshop software, provides a reliable way of measuring corneal vascular responses over time. (Optom Vis Sci 2012;89:215-220). © 2012 American Academy of Optometry.

Dumbleton,K., Woods,C. A., Jones,L. W., Fonn,D. The impact of contemporary contact lenses on contact lens discontinuation. Eye and Contact Lens 2012. [ Show Abstract ]

OBJECTIVES: Discontinuation or "dropout" from contact lens (CL) wear continues to afflict the CL industry. This study was conducted to determine whether the advent of new CL materials and designs has impacted the dropout rate and the reasons for discontinuation. METHODS: Current and lapsed CL wearers residing in Canada were recruited using Facebook to take part in an on line survey investigating CL wearing experiences during 2008 to 2010 and to establish the percentage of participants who temporarily and permanently discontinued CL wear during the period surveyed. RESULTS: Four thousand two hundred seven eligible surveys were received (64% female; median age 27 years). Forty percent had lapsed from lens wear for at least 4 months; however, 62% of the lapsed wearers (LWs) resumed wear. There were no differences between LWs and nonlapsed wearers (NLWs) with respect to gender; however, LWs were older, started lens wear when older, and had not worn lenses for as long as NLWs (all P<0.001). More NLWs than LWs wore silicone hydrogel CLs (49% vs. 38%, P<0.001) and more LWs than NLWs wore daily disposable lenses and hydrogel CLs (24% vs. 19% and 22% vs. 18%, respectively, P≤0.001). Primary reasons for discontinuation were discomfort (24%), dryness (20%), red eyes (7%), and expense (7%). Compliance with lens replacement was no different between LWs and NLWs (48% vs. 45%). CONCLUSIONS: About 23% of those surveyed had discontinued CL wear permanently. The primary reasons for dropping out continue to be discomfort and dryness. Dropout rates were lower in silicone hydrogel wearers.

Luensmann,D., Moezzi,A., Peterson,R. C., Woods,C., Fonn,D. Corneal staining and cell shedding during the development of solution-induced corneal staining. Optometry and Vision Science 2012;89,6:868-874. [ Show Abstract ]

Purpose. This non-dispensing cross-over study was conducted to determine if lenses presoaked in Opti-Free RepleniSH (OFR) or ReNu MultiPlus (RMP) cause solution-induced corneal staining (SICS) and subsequent cell sloughing before the typical 2 h in vivo examination point. Methods. Study lenses (PureVision) were worn bilaterally by 13 participants for periods of 15, 30, 60, and 120 min using two different contralateral care regimen pairings. The lens worn on the test eye was soaked overnight in either OFR or RMP and the control eye in Clear Care (CC). After lens removal, corneal staining was rated on a scale of 0 (negligible) to 100 (severe) for four peripheral quadrants and the central region, and the differential global staining score was calculated by subtracting baseline staining scores. Following the staining assessment, corneal cells were collected from the ocular surface using a non-contact irrigation system to determine ocular cell shedding rates. Results. Differential global staining score with OFR was greater than CC with the differences being statistically significant at 30 and 60 min (p 0.05). Conclusions. SICS occurred earlier but to a significantly lower degree when PureVision lenses were presoaked in OFR compared with RMP, while lenses presoaked in CC did not cause SICS. Ocular surface cell shedding after lens removal was not impacted by lens wear durations of ≤2 h. © 2012 American Academy of Optometry.

2011

Woods,C. A., Dumbleton,K., Jones,L., Fonn,D. Patient use of smartphones to communicate subjective data in clinical trials. Optometry and Vision Science 2011;88,2:290-294. [ Show Abstract ]

Purpose. Various methods have been used in clinical trials to collect time-sensitive subjective responses, including study diaries, telephone interviews, and use of text messaging. However, all of these methods are limited by the uncertainty of when the participants enrolled in the study actually record their responses. This technical note reports on the utility of the BlackBerry smartphone to collect such data and why such a system provides advantages over other methods to report subjective ratings in clinical studies. Methods. The Centre for Contact Lens Research developed an on-line web-enabled system that permits participants to record and immediately transmit subjective rating scores in numerical form directly into a web-enabled database. This, combined with the utility of BlackBerrys, enabled time-specific e-mail requests to be sent to the study participants and then for that data to be simultaneously transmitted to the web-enabled database. This system has been used in several clinical trials conducted at the Centre for Contact Lens Research, in which data were collected at various times and in several specific locations or environments. Results. In the clinical trials conducted using this system, participants provided responses on 97.5% of occasions to the requests for data generated by the automated system. When the request was for data on a set date, this method resulted in responses of 84.1% of the time. Conclusions.The series of clinical trials reported here show the benefits of the utilization of the BlackBerry to collect time- or environment-sensitive data via a web-enabled system. Copyright © 2011 American Academy of Optometry.

Dumbleton,K. A., Woods,C. A., Jones,L. W., Fonn,D. The relationship between compliance with lens replacement and contact lens-related problems in silicone hydrogel wearers. Contact Lens and Anterior Eye 2011;34,5:216-222. [ Show Abstract ]

To evaluate the relationship between compliance with replacement frequency (RF) and contact lens (CL)-related problems in silicone hydrogel (SiHy) wearers. Methods: 501 SiHy wearers from seven optometry offices completed surveys regarding their lens wear and any CL related problems which they may have experienced in the preceding 12 months. File review was subsequently conducted at their optometry offices to confirm the information provided. Results: 49% of respondents were wearing 2-week replacement (2WR) and 51% 1-month replacement (1MR) SiHy lenses. 67% wore their lenses for longer than the manufacturers' recommended RF (MRRF) and 60% for longer than their optometrist's recommended RF (ORRF). The mean RF was 2.6× the MRRF for 2WR and 1.5× for 1MR wearers (p< 0.001) with median values of 31 and 37 days, respectively. Twenty-three percent reported signs or symptoms consistent with potential complications relating to CL wear. This rate was significantly higher for wearers who were non-compliant with the ORRF than compliant wearers (26% versus 18%, p= 0.028). It was also higher for those multipurpose solution users who reported never/almost never rubbing and rinsing their lenses when compared with those who did this every night (29% versus 17%, p= 0.007). Conclusions: Two thirds of the SiHy wearers did not comply with the MRRF and 2WR wearers stretched the replacement interval of their lenses to a greater degree than 1MR wearers. Failing to replace lenses when recommended and failing to rub and rinse lenses were associated with a higher rate of patient-reported CL problems. © 2011 British Contact Lens Association.

Dumbleton,K. A., Woods,M., Woods,C. A., Jones,L. W., Fonn,D. Ability of patients to recall habitual contact lens products and enhancement of recall using photographic aids. Contact Lens and Anterior Eye 2011;34,5:236-240. [ Show Abstract ]

To determine the proportion of soft contact lens (CL) wearers who are able to recall their habitual products (lenses and care system) correctly from memory, and to evaluate the value of using photographic aids (PAs) to improve recall. Methods: 103 soft lens wearers attended 2 visits to investigate their habitual CL product use. At the first visit they were asked to recall which products they were using and then to identify their products from PAs. They returned for a second visit with their products for confirmation. Results: 51% correctly reported their lens brands from memory alone, which improved to 87% with the use of the PAs (p< 0.001). 41% correctly reported their habitual care system from memory alone, which improved to 80% with the use of PAs (p< 0.001). Females were better at recalling care system brand names than males (49% versus 27% correct, p= 0.040) and wearers with more than 1 year experience with their habitual CLs had better recall than those with up to 1 year experience (63% versus 27%, p= 0.014). Conclusion: Less than 50% of contact lens wearers were able to recall the names of their habitual lens and lens care products correctly from memory. PAs improved this recall significantly for both contact lenses and contact lens care systems. © 2011 British Contact Lens Association.

Keir,N. J., Simpson,T., Hutchings,N., Jones,L., Fonn,D. Outcomes of wavefront-guided laser in situ keratomileusis for hyperopia. Journal of cataract and refractive surgery 2011;37,5:886-893. [ Show Abstract ]

Purpose: To determine the impact of wavefront-guided laser in situ keratomileusis (LASIK) for hyperopia on corrected distance visual acuity (CDVA), contrast sensitivity, and higher-order aberrations (HOAs). Setting: Centre for Contact Lens Research, University of Waterloo, Waterloo, Ontario, Canada. Design: Case series. Methods: This study comprised patients who had LASIK for hyperopia. The HOAs up to the 4th order (5.0 mm pupil) in right eyes were analyzed. Results: The study enrolled 31 patients. The preoperative mean values were sphere, +2.60 diopters (D) ± 1.15 (SD) (range +1.00 to +5.00 D); astigmatism, -0.87 ± 0.74 D (range 0.00 to -3.75 D); and spherical equivalent (SE), +2.16 ± 1.00 D (range +0.63 to +4.50 D). The postoperative refractive SE was within ±0.50 D in 71.0% of eyes. The uncorrected distance visual acuity was 20/20 or better in 87.2% of eyes. There was no significant change in CDVA or contrast sensitivity (all P>.05). There was a significant change in Zernike coefficients Z(0,4), Z(-1,3), Z(-3,3), and Z(3,3) (range of mean absolute change ± SEM: 0.092 ± 0.013 μm to 0.208 ± 0.018 μm; all P<.001). Coefficients Z(-1,3) and Z(3,3) increased and Z(0,4) and Z(-3,3) decreased in magnitude; each had a reversal of sign. The only significant postoperative association was between low-contrast CDVA and Z(0,4) (r = 0.617, P<.001). Conclusions: Low-contrast CDVA after LASIK surgery for hyperopia was correlated with Z(0,4). There were no significant changes in CDVA or contrast sensitivity. The relative risk for losing low-contrast CDVA increased if more than 1 Zernike term had a sign change. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. © 2011 ASCRS and ESCRS.

Moezzi,A. M., Fonn,D., Varikooty,J., Richter,D. Distribution of overnight corneal swelling across subjects with 4 different silicone hydrogel lenses. Eye and Contact Lens 2011;37,2:61-65. [ Show Abstract ]

Purpose: To determine distribution of central corneal swelling (CCS) across subjects after 8 hr of sleep in eyes wearing silicone hydrogel lenses with various oxygen transmissibility (Dk/t) values and in eyes without lenses. Methods: Twenty-nine neophytes wore lotrafilcon A (Dk, 140), balafilcon A (Dk, 91), galyfilcon A (Dk, 60), and senofilcon A (Dk, 103) lenses in powers -3.00, -10.00, and +6.00 diopters on separate nights, in random order, and on 1 eye only. The contralateral eye (no lens) served as the control. Central corneal thickness was measured using a digital optical pachometer before lens insertion and immediately after lens removal on waking. Results: The average difference between the mean (7%) and the median (6.8%) CCS of all lenses was only 0.2%, suggesting a normal distribution. There was no correlation between the mean and the range of the CCS (r=0.058, P=0.766). Normal CCS distributions were also found with each lens-wearing eye and the control eye (P>0.20 for all). There was a significant correlation between lens-wearing eye and control eye (r=0.895, P<0.001) and between lotrafilcon A and each of the other 3 lenses for mean CCS across the study participants (P<0.001 for all). Conclusions: Distribution of corneal swelling in both lens-wearing eye and control eye followed a normal curve. An individual's corneal swelling response seems to be independent of lens type. © 2011 Lippincott Williams & Wilkins.

Szczotka-Flynn,L., Benetz,B. A., Lass,J., Albright,M., Gillespie,B., Kuo,J., Fonn,D., Sethi,A., Rimm,A. The association between mucin balls and corneal infiltrative events during extended contact lens wear. Cornea 2011;30,5:535-542. [ Show Abstract ]

PURPOSE:: To determine the association between mucin ball formation and corneal infiltrative events (CIEs) during continuous wear with lotrafilcon A silicone hydrogel contact lenses. METHODS:: Subjects (n = 205) in the Longitudinal Analysis of Silicone Hydrogel Contact Lens Study wore lotrafilcon A contact lenses for 12 months of continuous wear. The primary outcome was a CIE. Kaplan-Meier methods were used to estimate the unadjusted cumulative incidence of remaining CIE free stratified by mucin ball presence. Cox proportional hazards regression was used to model the hazard of developing a CIE as a function of mucin ball formation and other covariates. RESULTS:: Over half (54.2%) of the subjects displayed some presence of mucin balls during at least 1 visit and about one third (32.8%) displayed repeated episodes. Mucin ball scores were correlated between the 2 eyes and weakly correlated with corneal curvature (P ≤ 0.005). Univariate analyses revealed that the relative hazard for a CIE was 0.35 [95% confidence interval (CI), 0.19-0.68] if a single episode of mucin balls was detected and 0.17 (95% CI, 0.06-0.43) if repeated episodes were detected. Upon multivariate analysis, repeated presence of mucin balls was associated with an 84% decreased hazard of experiencing a CIE (hazard ratio: 0.16; 95% CI, 0.06-0.44). CONCLUSIONS:: The presence of mucin balls is significantly associated with a decreased incidence of CIEs, and the effect is greatest when they are repeatedly present over time. We hypothesize that the mucin ball presence represents a more concentrated or viscous mucus layer, which prevents upregulation of the immune response against bacterial ligands. Copyright © 2011 by Lippincott Williams & Wilkins.

2010

Dumbleton,K., Richter,D., Woods,C., Jones,L., Fonn,D. Compliance with contact lens replacement in Canada and the United States. Optometry and Vision Science 2010;87,2:131-139. [ Show Abstract ]

PURPOSE.: To assess eye care practitioners (ECPs) recommendations for replacement frequency (RF) of silicone hydrogel (SH) and daily disposable (DD) lenses in Canada and the U.S. and to compare noncompliance (NC) with manufacturer recommended RF by the ECP and patient, and the reasons given for NC. METHODS.: Invitations to participate were sent by e-mail to ECPs in Canada and the U.S. Twenty patient surveys were sent to 420 ECPs, and 2232 eligible surveys were received from 216 ECPs (26% Canada, 74% U.S.). Questions related to patient demographics, lens type, wearing patterns, ECP instructions for RF, and actual patient RF. ECPs provided lens information and their recommendation for RF after the surveys were completed and sealed in envelopes. Responses were anonymous. RESULTS.: DD accounted for 18% (Canada) vs. 16% (U.S.) of wearers (p > 0.05); 35% (Canada) vs. 45% (U.S.) wore 2-week replacement SH (2WR; p = 0.011); and 47% (Canada) vs. 39% (U.S.) wore 1-month replacement SH (1MR) lenses (p = 0.025). Thirty-four percent (Canada) vs. 18% (U.S.) of ECPs recommended longer RFs than the manufacturer recommended RF for 2WR lens wearers (p 0.05) and were lowest for DD (13% Canada, 12% U.S.), followed by 1MR (33% Canada, 28% U.S.). The highest NC rates were with 2WR (50% Canada, 52% U.S.). The most frequent reason for NC with 2WR and 1MR was 'forgetting which day to replace lenses' (54% Canada, 53% U.S.) and in DD wearers 'to save money' (56% Canada, 29% U.S., p < 0.001). CONCLUSIONS.: 1MR lenses are more frequently prescribed in Canada. ECPs in Canada were NC with 2WR lenses more frequently than U.S. ECPs, but patient NC rates were the same in both countries for all lens types. ECP and patient NC rates were highest for 2WR lens wearers. Copyright © 2010 American Academy of Optometry.

Dumbleton,K., Woods,C., Jones,L., Richter,D., Fonn,D. Comfort and vision with silicone hydrogel lenses: Effect of compliance. Optometry and Vision Science 2010;87,6:421-425. [ Show Abstract ]

PURPOSE. Silicone hydrogel (SH) lenses are usually replaced after 2 weeks (2W) or 1 month (1M); however, many patients do not comply with the manufacturers' recommended replacement frequency (MRRF). The purpose of this analysis was to investigate the effect of compliance with MRRF on comfort and vision in SH wearers. METHODS. As a part of a larger study investigating compliance with MRRF, patients were asked to rate their subjective comfort and vision from 0 (very poor) to 10 (excellent) in the morning, at the end of the day (EVE), when lenses were new, and needed replacing (NR). RESULTS. One thousand three hundred forty-four patients wore 2W replacement modality (2WR) (n = 717) or 1M replacement modality (1MR) (n = 617) SH lenses. Comfort and vision in the morning and when lenses are new were significantly higher than for EVE and NR (p < 0.001). Twenty-nine percent (95% confidence interval 25.3-32.4) of 1MR and 59% (95% confidence interval 55.5-62.7) of 2WR wearers were non-compliant with the MRRF. Compliance had a significant effect on EVE (p = 0.002, p = 0.008) and NR (p < 0.001, p < 0.001) comfort and vision. After accounting for compliance, EVE and NR comfort and EVE vision were higher for 1MR than 2WR (p = 0.015, p = 0.044, p = 0.019). CONCLUSIONS. Compliant patients had better EVE and NR comfort and vision than non-compliant patients, regardless of replacement modality. Optimal subjective performance with SH lenses seems to be facilitated by replacing lenses as recommended. Copyright © 2010 American Academy of Optometry.

Fonn,D. Editorial: Myopia control and new editorial board members. Eye and Contact Lens 2010;36,4:189.

Fonn,D. It's a new day. Eye and Contact Lens 2010;36,3:139.

Fonn,D. Just what do we mean by clinical significance. Eye and Contact Lens 2010;36,1:1.

Fonn,D. Editorial: Concerned parents and patients. Eye and Contact Lens 2010;36,2:67.

Fonn,D. What goes around comes around. Eye and Contact Lens 2010;36,6:323.

Fonn,D., Peterson,R., Woods,C. Corneal staining as a response to contact lens wear. Eye and Contact Lens 2010;36,5:318-321. [ Show Abstract ]

Objective: To review the effects of contact lenses on the corneal surface. Methods: A review of the literature and in-house research of corneal staining and its various forms of presentation. Results: Corneal staining manifests in many different forms. The severity of staining or insult of the cornea is usually determined by the extent (area of coverage), density, and depth. The cause of staining is multifactorial, and its location is often linked to the type of lens that is being worn, the solution used to clean/disinfect the lens, the state of hydration of the soft lens, and the state of the cornea that has been affected by the lens. Conclusions: Sodium fluorescein dye effectively highlights corneal integrity changes referred to as corneal staining. This review describes the manifestations, the cause, the mechanisms, and the methods of remediation of corneal staining. © 2010 Lippincott Williams & Wilkins.

Keir,N., Simpson,T., Fonn,D. Visual and optical performance of silicone hydrogel contact lenses for moderate myopia. Journal of Optometry 2010;3,3:149-157. [ Show Abstract ]

Purpose: To compare the short-term visual and optical performance of silicone hydrogel contact lenses for myopia = -3.00D. Methods: This was a short-term, non-dispense, double-masked, randomized study investigating Night&Day (ND), PureVision (PV), O2 Optix (O2), Biofinity (BF), Acuvue Advance (AA) and Acuvue OASYS for myopia = -3.00D. Testing was conducted under scotopic conditions. Measures (one eye only) included: high- and low-contrast visual acuity (HCVA/LCVA), contrast sensitivity, subjective clarity of vision ratings (0-100 scale using reference images, with test image representing grade 50) and ocular aberrations (up to the 4th order, analyzed across individual scotopic pupil sizes). Results: Three males and 27 females participated, with a mean (± SD) age of 24.9 ± 7.7 yrs (range 19 to 53 yrs), sphere of -5.30 ± 1.73D (range -3.00 to -10.75D) and cylinder -0.36 ± 0.23D (range 0 to -0.75D). Mean (± SEM) logMAR HCVA ranged from 0.06 (PV) to 0.10 (AA) (± 0.02), LCVA from 0.33 (BF) to 0.40 (AA) (± 0.02) and contrast sensitivity from 2.33 (BF) to 2.53 (ND) (± 0.15) (differences not statistically significant; all p > 0.05). Subjective ratings for the test image ranged from 59 (PV) to 64 (ND) (± 4) and 56 (AA) to 65 (ND) (± 4), for monochromatic and polychromatic reference images, respectively (all p > 0.05). There was a statistically significant impact on ocular aberrations with all study lenses compared to no lens. Between-lens differences were statistically significant for defocus (Z 0 2), horizontal coma (Z 1 3) and spherical aberration (Z 0 4). Conclusions: Despite some differences in ocular aberrations, there were no significant differences in HCVA, LCVA, contrast sensitivity or subjective ratings across lenses. © 2010 Spanish General Council of Optometry. Published by Elsevier España, S.L. All rights reserved.

Peterson,R. C., Fonn,D., Woods,C. A., Jones,L. Impact of a rub and rinse on solution-induced corneal staining. Optometry and Vision Science 2010;87,12:1030-1036. [ Show Abstract ]

Purpose.: To investigate whether the inclusion of a rub and rinse step before contact lens disinfection has an impact on solution-induced corneal staining. Methods.: This was a prospective, double-masked, single investigator study. Twenty participants were recruited for two visits, where balafilcon-A lenses were worn bilaterally for 2 h. Each pair of lenses was prepared using two different methodologies. The "control" lens was transferred from the blister pack directly into a storage case containing polyhexamethylene biguanide-based lens care solution. The contralateral "test" lens was rubbed and simultaneously rinsed using the same polyhexamethylene biguanide-based care solution, for either 60 s (visit 1) or 20 s (visit 2). Both lenses were then soaked in the solution overnight. After baseline corneal staining assessments, the lenses were inserted following a randomized contralateral model. After 2 h, lenses were removed, corneal staining was regraded, and comfort scores were obtained. Results.: Rubbed and rinsed test lenses induced significantly less corneal staining than control lenses for all participants during visit 1 (mean ± SD: 516 ± 843 vs. 2170 ± 902; p 0.05). Conclusions.: Corneal staining induced after 2 h of lens wear with the combination of balafilcon-A and polyhexamethylene biguanide-based lens care solution can be significantly reduced by including a rub and rinse step before overnight soaking. Further work is required to establish the longevity of this effect during the monthly wearing cycle. Copyright © 2010 American Academy of Optometry.

Situ,P., Simpson,T. L., Jones,L. W., Fonn,D. Effects of silicone hydrogel contact lens wear on ocular surface sensitivity to tactile, pneumatic mechanical, and chemical stimulation. Investigative Ophthalmology and Visual Science 2010;51,12:6111-6117. [ Show Abstract ]

PURPOSE. To determine the effects of silicone hydrogel lens wear and lens-solution interactions on ocular surface sensitivity. METHODS. Forty-eight adapted lens wearers completed the study, which comprised two phases. Phase 1 included habitual lens wear, no lens wear (7 ± 3 days), and balafilcon A lenses (PV; PureVision; Bausch & Lomb, Rochester, NY) with a hydrogen peroxide-based regimen for 2 weeks; phase 2 included wear of PV with the use of a multipurpose solution containing either polyhexamethylene-biguanide (PHMB) or Polyquad/Aldox (Alcon Laboratories, Fort Worth, TX) preservative, each for 1 week, with a 2-week washout period between solutions. Tactile and pneumatic (mechanical and chemical) stimuli were delivered, and thresholds were determined by Cochet-Bonnet (Luneau Ophthalmologie, Chartres, France) and Belmonte (Cooperative Research Centre for Eye Research and Technology, Sydney, NSW, Australia) pneumatic esthesiometers, respectively. Corneal and conjunctival thresholds and staining scores were assessed at baseline, after 2 and 8 hours of lens wear on day 1 and at the end of each wearing cycle (2 hours). RESULTS. In phase 1, compared to the no-lens baseline, corneal tactile thresholds increased at the 1-day, 8-hour and the 2-week visits (P < 0.05), whereas conjunctival mechanical thresholds decreased at the 1-day, 2-hour and the 2-week visits (P < 0.05). In phase 2, the chemical thresholds were lower with PHMBpreserved solution compared with the Polyquad/Aldox system at the 1-day, 2-hour and the 1-week visits (P < 0.05). Staining scores correlated inversely with conjunctival chemical thresholds (all P < 0.05). CONCLUSIONS. Ocular surface sensitivity changed in adapted lens wearers, when lenses were refit after a no-lens interval and during lens wear with different care regimens. The corneal staining that was observed with certain lens-solution combinations was accompanied by sensory alteration of the ocular surface-that is, higher levels of staining correlated with increased conjunctival chemical sensitivity. © Association for Research in Vision and Ophthalmology.

Sorbara,L., Maram,J., Fonn,D., Woods,C., Simpson,T. Metrics of the normal cornea: Anterior segment imaging with the Visante OCT. Clinical and Experimental Optometry 2010;93,3:150-156. [ Show Abstract ]

Purpose: The purpose of the study was to obtain anterior segment biometry for 40 normal eyes and to measure variables that may be useful to design large diameter gas permeable contact lenses that sit outside the region normally viewed by corneal topographers. Also, the distribution of these variables in the normal eye and how well they correlated to each other were determined. Methods: This is a cross-sectional study, in which data were collected at a single study visit. Corneal topography and imaging of the anterior segment of the eye were performed using the Orbscan II and Visante OCT. The variables that were collected were horizontal K reading, central corneal/scleral sagittal depth at 15 mm chord, and nasal and temporal angles at the 15 mm chord using the built-in software measurement tools. Results: The central horizontal K readings for the 40 eyes were 43 ± 1.73 D (7.85 ± 0.31 mm), with ± 95% confidence interval (CI) of 38.7 (8.7 mm) and 46.6 D (7.24 mm). The mean corneal/scleral sagittal depth at the 15 mm chord was 3.74 ± 0.19 mm and the range was 3.14 to 4.04 mm. The average nasal angle (which was not different from the temporal angle) at the 15 mm chord was 39.32 ± 3.07 degrees and the ± 95%CI was 33.7 and 45.5 degrees. The correlation coefficient comparing the K reading and the corneal/scleral sagittal depth showed the best correlation (0.58, p < 0.001). The corneal/scleral sagittal depth at 15 mm correlated less with the nasal angle (0.44, p = 0.004) and the weakest correlation was for the nasal angle at 15 mm with the horizontal readings (0.32, p = 0.046). Conclusion: The Visante OCT is a valuable tool for imaging the anterior segment of the eye. The Visante OCT is especially effective in providing the biometry of the peripheral cornea and sclera and may help in fitting GP lenses with a higher percentage of initial lens success, when the corneal sag and lens sag are better matched. © 2010 The Authors. Journal compilation © 2010 Optometrists Association Australia.

Varikooty,J., Keir,N., Woods,C. A., Fonn,D. Measurement of the refractive index of soft contact lenses during wear. Eye and Contact Lens 2010;36,1:2-5. [ Show Abstract ]

Purpose: To determine whether the refractive index (RI) of a soft contact lens can be evaluated using refractometry while the lens remains on the eye and to compare this with more traditional ex vivo RI measurements. Methods: A slitlamp apparatus was modified to incorporate a customized Atago hand refractometer. With a double-masked study design, nine adapted symptomatic soft contact lens wearers wore a contact lens in each eye (lotrafilcon B and etafilcon A) in a randomized order. In vivo RI was determined from the relative Brix scale measurements immediately after lens insertion and after 1 and 10 hr of lens wear. Ex vivo refractometry was performed after 10 hr of lens wear for comparison. Means ± standard errors of the means are reported. Results: In vivo RI values at baseline were 1.422 ± 0.0004 (lotrafilcon B) and 1.405 ± 0.0021 (etafilcon A); after 1 hr of lens wear, values were 1.423 ± 0.0006 and 1.408 ± 0.0007, respectively; and after 10 hr of lens wear, values were 1.424 ± 0.0004 and 1.411 ± 0.0010, respectively. Ex vivo RI values at the end of the 10 hr wearing period were 1.424 ± 0.0003 (lotrafilcon B) and 1.412 ± 0.0017 (etafilcon A). The change in in vivo RI across the day was statistically significant for the etafilcon A lens (repeated-measures analysis of variance, P0.05). Conclusions: This novel adaptation of refractometry was able to measure the RI of soft contact lenses during wear (without lens removal). End of day RI measurements using in vivo and ex vivo refractometry were comparable with each other. Future work is required to determine whether this in vivo method can improve our understanding of the relationships between soft contact lens RI, hydration, on-eye lens performance, and symptomology. Copyright © Contact Lens Association of Ophthalmologists, Inc.

2009

Woods,J., Woods,C. A., Fonn,D. Early symptomatic presbyopes-What correction modality works best?. Eye and Contact Lens 2009;35,5:221-226. [ Show Abstract ]

Purpose: To compare the performance of a low-addition silicone hydrogel multifocal soft lens with other soft lens correction options in a group of habitual soft lens wearers of distance correction who are symptomatic of early presbyopia. METHOD: This clinical study was designed as a prospective, double-masked, randomized, crossover, dispensing trial consisting of four 1-week phases, one for each of the correction modalities: a low-addition silicone hydrogel multifocal soft lens, monovision, habitual correction, and optimized distance visual correction. The prescriptions of all modalities were finalized at a single fitting visit, and the lenses were worn according to a randomized schedule. All lenses were made from lotrafilcon B material. A series of objective vision tests were conducted: high- and low-contrast LogMAR under high- and low-room lighting conditions, stereopsis, and critical print size. A number of other data collection methods used were novel: some data were collected under controlled laboratory-based conditions and others under "real-world" conditions, some of which were completed on a BlackBerry hand-held communication device. RESULTS: All participants were able to be fit with all four correction modalities. Objective vision tests showed no statistical difference between the lens modalities except in the case of low-contrast near LogMAR acuity under low-lighting levels where monovision (+0.29 ± 0.10) performed better than the multifocal (+0.33 ± 0.11, P=0.027) and the habitual (+0.37 ± 0.12, P<0.001) modalities. Subjective ratings indicated a statistically better performance provided by the multifocal correction compared with monovision, particularly for the vision associated with driving tasks such as driving during the daytime (93.3 ± 8.8 vs. 84.2 ± 23.7, P=0.05), at nighttime (88.8 ± 11.7 vs. 74.9 ± 23.6, P=0.001), any associated haloes or glare (92.0 ± 10.6 vs. 78.0 ± 22.8, P=0.003), and observing road signs (90.1 ± 11.8 vs. 79.4 ± 20.2, P=0.027). Preference for the multifocal compared with monovision was also reported when watching television (95.0 ± 6.4 vs. 82.6 ± 20.1, P=0.001) and when changing focus from distance to near (87.0 ± 13.4 vs. 66.1 ± 32.2, P<0.001). CONCLUSIONS: For this group of early presbyopes, the AIR OPTIX AQUA MULTIFOCAL-Low Add provided a successful option for visual correction, which was supported by the results of subjective ratings, many of which were made during or immediately after performing such activities as reading, using a computer, watching television, and driving. These results suggest that making a prediction of "success or not" based on consulting room acuity tests alone is probably unwise. Copyright © Contact Lens Association of Ophthalmologists, Inc.

Dumbleton,K., Woods,C., Fonn,D. An investigation of the efficacy of a novel ocular lubricant. Eye and Contact Lens 2009;35,3:149-155. [ Show Abstract ]

OBJECTIVE: To investigate the efficacy of a novel ocular lubricant compared with a commercially marketed ocular lubricant in a group of noncontact lens wearers currently using over-the-counter products for the management of symptoms of moderate to severe dry eye. METHODS: This was a prospective, double-masked study that randomized 110 subjects in a ratio of 1:1 to receive a novel ocular lubricant (test group) or a marketed ocular lubricant (control group). Subjects were instructed to instill the lubricant eye drops at least three times daily. After enrollment, subjects were evaluated at baseline and at 7 and 30 days. They were also required to complete a series of home-based subjective questionnaires after 15 days. Main outcomes were subjective symptoms and objective clinical assessment at 7 and 30 days. RESULTS: The test group had higher overall comfort ratings than the control group (P = 0.012). Seventy-one percent of the test group and 57% of the control group said the drops used "somewhat" or "definitely" improved ocular comfort; 62% of the test group had greater end-of-day comfort compared with 45% of the control group (P = 0.015). There were no between-group differences in visual acuity, tear quality or quantity, corneal staining, conjunctival staining, or bulbar and limbal conjunctival hyperemia. CONCLUSIONS: The novel ocular lubricant offers equivalent or superior comfort compared with a marketed lubricant eye drop. Objective clinical outcomes were not statistically significantly different between the two groups. © 2009 Lippincott Williams & Wilkins.

Dumbleton,K., Woods,C., Jones,L., Fonn,D., Sarwer,D. B. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement in the United States. Eye and Contact Lens 2009;35,4:164-171. [ Show Abstract ]

OBJECTIVE: The objectives of this study were to assess current recommendations for replacement frequency (RF) of silicone hydrogel (SH) and daily disposable (DD) lenses, to determine compliance with these recommendations, and to investigate the reasons given for noncompliance. METHODS: A package containing 20 patient surveys was sent to 309 eye care practitioners (ECPs) in the United States who had agreed to participate in the study. One thousand eight hundred fifty-nine completed surveys were received from 158 ECPs and 1,654 surveys were eligible for analysis. Questions related to patient demographics, lens type, lens wearing patterns, the ECP instructions for RF, and the actual patient reported RF. ECPs were asked to provide lens information and their recommendation for RF after the surveys had been completed and sealed in envelopes. All responses were anonymous. RESULTS: Sixty-six percent of patients were women and their mean age was 34 ± 12 years. Eighty-eight percent of lenses were worn for daily wear, 12.8 ± 3.2 hours a day, 6.2 ± 1.5 days a week. Lens type distribution was 16% DD, 45% 2 week (2W) SH, and 39% 1 month (1M) SH. ECP recommendations for RF varied according to the lens type; 1% of 1M (95% CI 0.2-1.7), 4% of DD (95% CI 2.1-7.2), and 18% of 2W (95% CI 15.1-20.7) patients were given instructions that did not conform to the manufacturers' recommended RF (MRRF). When considering only those patients who were given the correct instructions for RF, 38% were not compliant with the MRRF; noncompliance rates varied according to the lens type and were 12% for DD (95% CI 8.6-17.2), 28% for 1M (95% CI 24.9-32.1), and 52% for 2W (95% CI 47.8-55.8). The most frequent reasons for over wearing lenses were "forgetting which day to replace lenses" (51%) and "to save money" (26%). Fifty-three percent believed that a reminder system would aid compliance; the most popular methods being a cell phone reminder or text message (29%) and a nominated day each week or month (26%). Discussions between the ECPs and the patients were more extensive for patients who were compliant with the MRRF. CONCLUSIONS: ECPs recommended RFs more frequently with DD and 1M SH lenses than with 2W SH lenses, consistent with manufacturers' recommendations. Patients were less compliant with RF than ECPs for all lens types investigated. Patients were most compliant with RF when wearing DD lenses and least compliant when wearing 2W SH lenses. Better communication facilitated greater compliance with RF. More than half of those not replacing lenses, when recommended, reported that this was because they forgot which day to replace their lenses. © 2009 Lippincott Williams & Wilkins, Inc.

Keir,N. J., Simpson,T., Jones,L. W., Fonn,D. Wavefront-guided LASIK for myopia: Effect on visual acuity, contrast sensitivity, and higher order aberrations. Journal of Refractive Surgery 2009;25,6:524-533. [ Show Abstract ]

PURPOSE: To determine the impact of wavefrontguided LASIK for myopia with or without astigmatism on high and low contrast best spectacle-corrected visual acuity (BSCVA), photopic and mesopic contrast sensitivity, and higher order aberrations. METHODS: Bilateral wavefront-guided LASIK (LADARVision4000; Hansatome microkeratome) was performed on 324 eyes (162 patients) with a mean spherical manifest refraction of -2.84±1.35 diopters (D) (range: -0.25 to -6.50 D) and astigmatism of -0.81±0.74 D (range: 0 to -4.00 D). Mean age was 37.7±9.3 years (range: 20 to 60 years). Best spectacle-corrected visual acuity and contrast sensitivity were assessed using ETDRS charts and vertical sinusoidal gratings, respectively. Higher order aberrations were measured using a Shack-Hartmann wavefront sensor, analyzed across a 5-mm pupil. Repeated measures and post hoc analyses determined statistical significance (P<.0025). Only right eyes were analyzed. RESULTS: One hundred thirty-six eyes (84%) had uncorrected visual acuity of 20/20 or better 6 months postoperative; 80.9% (131 eyes) were within ±0.50 D of attempted correction. Statistically significant postoperative improvements were noted in high and low contrast BSCVA (both P≤.001); in photopic contrast sensitivity at 3, 6, and 12 cycles per degree (cpd); and in mesopic contrast sensitivity at 12 and 18 cpd (all P<.001). With respect to higher order aberrations, a statistically significant change was seen in Zernike coefficients Z 3 -1, Z 3 1, Z 3 -3, Z 3 3, and Z 3 4 following surgery (range of mean absolute change: 0.042 to 0.142 μm; all P<.001). All increased in magnitude except for Z 3 -3, which decreased. CONCLUSIONS: Despite an increase in higher order aberrations, wavefront-guided LASIK yields excellent visual acuity and contrast sensitivity. Spherical aberration, which increases the most following non-wavefront-guided LASIK, showed no significant change.

Papas,E. B., Decenzo-Verbeten,T., Fonn,D., Holden,B. A., Kollbaum,P. S., Situ,P., Tan,J., Woods,C. Utility of short-term evaluation of presbyopic contact lens performance. Eye and Contact Lens 2009;35,3:144-148. [ Show Abstract ]

OBJECTIVES: To establish if evaluations of multifocal contact lens performance conducted at dispensing are representative of behavior after a moderate adaptation period. METHODS: Eighty-eight presbyopic subjects, across four clinical sites, wore each of four multifocal soft contact lenses (ACUVUE BIFOCAL, Focus Progressives, Proclear Multifocal, and SofLens Multifocal) for 4 days of daily wear. Comprehensive performance assessments were conducted at dispensing and after 4 days wear and included the following objective metrics: LogMAR acuity (contrast, 90% and 10%; illumination, 250 and 10 cd/m; distance, 6 m, 100 cm, and 40 cm), stereopsis (RANDOT), reading critical print size and maximum speed and range of clear vision at near. Subjective assessments were made, with 100-point numerical rating scales, of comfort, ghosting (distance, near), visual quality (distance, intermediate, and near), and the appearance of haloes. At two sites, subjects (n = 39) also rated visual fluctuation (distance, intermediate, and near), facial recognition, and overall satisfaction. RESULTS: Among the objective variables, significant differences (paired t test, P<0.05) between dispensing and 4 days were found only for range of clear vision at near (2.9 ± 2.0 cm; mean difference ± standard deviation) and high contrast near acuity in low illumination (-0.013 ± 0.011 LogMAR). With the exception of insertion comfort, all subjective variables showed significant decrements over the same period. Overall satisfaction declined by an average of 10.9 ± 5.1 points. CONCLUSIONS: Early assessment is relatively unrepresentative of performance later on during multifocal contact lens wear. Acuity based measures of vision remain substantially unchanged over the medium term, apparently because these metrics are insensitive indicators of performance compared with subjective alternatives. © 2009 Lippincott Williams & Wilkins.

Sorbara,L., Peterson,R., Woods,C., Fonn,D. Multipurpose disinfecting solutions and their interactions with a silicone hydrogel lens. Eye and Contact Lens 2009;35,2:92-97. [ Show Abstract ]

PURPOSE:: To assess the compatibility of a new silicone hydrogel lens, asmofilcon A (with four multipurpose disinfecting solutions: OPTIFREE RepleniSH, ReNu MultiPlus, Solo-Care Aqua and MeniCare Soft). Ocular responses and subjective responses were monitored with each lens-care system combination. METHODS:: The study was conducted as a prospective, bilateral, clinical trial with a single-masked investigator, and randomized cross-over design with four phases, (one for each care system). Each study phase comprised of two consecutive days of lens wear where the lenses were inserted on day 1 directly from the blister-packs and worn for over 8 hr, then inserted on day 2 after overnight disinfection with one of the study lens care systems. Twenty-five adapted soft contact lens wearers who were able to wear their habitual lenses comfortably for more than 12 hr were recruited. RESULTS:: There were statistically significant differences in corneal staining found for all the lens-care systems when comparing the results of day 1 (from the blister pack) with day 2 (following care system use) (P < 0.05). ReNu MultiPlus solution had the highest grade for corneal staining at the 2-hr time point on day 2 which then decreased by 6 hr (P < 0.05). There was no difference between the lens care systems and the rating of subjective comfort over either of the two days. The rating of dryness and burning sensations were only slightly increased at 6 hr for all lens care systems except ReNu MultiPlus where burning was highest on insertion (P < 0.05). CONCLUSION:: Corneal staining observed in this study does not seem to have been related to the presence of polyhexamethylene biguanide (0.0001% wv) that was present in three of the four care systems. Only one care system (ReNu MultiPlus) demonstrated an associated level of corneal staining that was statistically significant; however, this was not considered to be of clinical relevance. These results suggest that using this novel surface-treated silicone hydrogel lens may result in less lens and lens care-related interactions. © 2009 Lippincott Williams & Wilkins.

2008

Dumbleton,K. A., Woods,C. A., Jones,L. W., Fonn,D. Comfort and adaptation to silicone hydrogel lenses for daily wear. Eye and Contact Lens 2008;34,4:215-223. [ Show Abstract ]

Objectives. To investigate initial comfort and adaptation of currently successful low oxygen transmissibility soft lens wearers refitted with silicone hydrogel (SH) lenses for daily wear. Methods. Fifty-five subjects were enrolled in a subject-masked 5-month clinical trial in which they wore 5 SH lenses in a randomized, crossover design. Comfort, burning, and dryness were rated on scales of 0 to 100 immediately on insertion and the time for lens settling was recorded. Symptoms were then rated at various times, using BlackBerry wireless communication devices (Research in Motion, Waterloo, Canada), during the day for 2 cycles of 2 weeks wear for each lens type. Results. Comfort immediately on insertion varied between lens types (P=0.002). All lens types were reported by the subjects to have settled within 30 to 45 sec of insertion (P=0.14) and "settled" comfort was greater than comfort immediately on insertion (P<0.001). Comfort within the first hour of wear also varied between lens types (P=0.02). Comfort during the day decreased significantly for all lenses (P=0.001), but there was no difference between lenses (P=0.19) and no effect of lens age (P=0.15). The wearing times were greater with the SH lenses than the habitual lenses worn before study commencement (P=0.001). Overall performance of the lenses after 4 weeks was high, with no difference between lenses (P=0.45). Conclusions. Initial comfort and adaptation to all SH lenses were good and no differences in the overall ratings were found between the 5 SH lenses investigated. Decreased comfort was noted later in the day with all lens types, but longer wearing times were reported with the SH lenses than previous hydroxyethyl methacrylate-based lenses. © 2008 Contact Lens Association of Ophthalmologists, Inc.

Haque,S., Fonn,D., Simpson,T., Jones,L. Epithelial thickness changes from the induction of myopia with CRTH RGP contact lenses. Investigative Ophthalmology and Visual Science 2008;49,8:3345-3350. [ Show Abstract ]

PURPOSE. To investigate changes in epithelial thickness after overnight wear of CRTH rigid gas-permeable (RGP) lenses (Paragon Vision Sciences, Mesa, AZ) for the correction of hyperopia. METHODS. Twenty subjects wore a +3.50 D hyperopia-correcting CRTH lens on one eye for a single night in an attempt to induce myopia (first study). The untreated eye served as the control. Corneal and epithelial thickness was measured at nine points across the horizontal meridian by OCT. Measurements were obtained the night before lens wear, immediately after lens removal the next morning, and 1, 3, 6, and 12 hours after removal. Measurements were obtained 28 hours later, to observe recovery. Then, the attempted hyperopic corrections of +1.50 and +3.50 D were evaluated, using CRTH lenses in both eyes of 20 subjects for a single night (second study). RESULTS. All values were compared to baseline unless otherwise stated. In the first study, the treated eye's central and midperipheral epithelial thickness increased by 21.5% ± 8.6% and 13.3% ± 7.6%, respectively, after lens removal (P < 0.001). The control eye's central epithelial thickness (CET) increased by 7.1% ± 6.0% (P < 0.05). In the second study, CET increased by 17.6% ± 8.5% (P < 0.001) in the +3.50 D-treated eye and by 13.3% ± 4.8% (P < 0.001) in the +1.50 D-treated eye. Midperipheral epithelial thickening was 5.9% ± 4.7% (P < 0.05) in the +3.50 D-treated eye and 6.0% ± 6.3% (P < 0.05) in the +1.50 D-treated eye. CONCLUSIONS. CRTH lenses, designed to correct hyperopia, when worn overnight, caused an increase in CET. The amount of epithelial change seemed to differ with modified lens design. Copyright © Association for Research in Vision and Ophthalmology.

Lu,F., Simpson,T., Sorbara,L., Fonn,D. Malleability of the ocular surface in response to mechanical stress induced by orthokeratology contact lenses. Cornea 2008;27,2:133-141. [ Show Abstract ]

PURPOSE: To determine the malleability of the ocular surface by examining the acute effects of local mechanical stress on optical performance, corneal shape, and corneal/epithelial thickness after corneal refractive therapy for myopia and hyperopia (CRT and CRTH). METHODS: Twenty ametropes (spherical equivalent: -2.08 ± 2.31 D) wore CRT and CRTH lenses in a random order on 1 eye (randomly selected). The lenses were worn for 15, 30, and 60 minutes (randomly ordered, with each period taking place on a different day). Refractive error, aberrations, corneal topography, and corneal/epithelial thickness (using OCT) were measured before and after lens wear. The measurements were performed on the control eyes at the 60-minute visit only. RESULTS: With both CRT and CRTH lens wear, significant changes occurred in many parameters from the 15-minute time point. The refractive error and defocus decreased after CRT lens wear (all P 0.05). Higher-order aberrations, including coma and spherical aberration (SA), increased after CRT and CRTH lens wear (all P 0.05). Higher-order aberrations, including coma and spherical aberration (SA), increased after CRT and CRTH lens wear (all P 0.05). Higher-order aberrations, including coma and spherical aberration (SA), increased after CRT and CRTH lens wear (all P 0.05). Higher-order aberrations, including coma and spherical aberration (SA), increased after CRT and CRTH lens wear (all P 0.05). Higher-order aberrations, including coma and spherical aberration (SA), increased after CRT and CRTH lens wear (all P 0.05). Higher-order aberrations, including coma and spherical aberration (SA), increased after CRT and CRTH lens wear (all P 0.05). Higher-order aberrations, including coma and spherical aberration (SA), increased after CRT and CRTH lens wear (all P 0.05). CONCLUSIONS: CRT lenses for myopia and hyperopia induce significant structural and optical changes in as little as 15 minutes. The cornea, particularly the epithelium, is remarkably malleable, with rapid steepening and flattening possible in little time. © 2008 Lippincott Williams & Wilkins, Inc.

Simpson,T., Fonn,D. Optical coherence tomography of the anterior segment. Ocular Surface 2008;6,3:117-127. [ Show Abstract ]

Perhaps no diagnostic technology has emerged as rapidly in ophthalmology as optical coherence tomography (OCT). A single clinical device for this noninvasive imaging technique was first released in 1996, and now at least ten clinical devices are available. Although the first clinical anterior segment OCT was marketed only 2 years ago, a substantial amount of work has been done using modified retinal imagers or prototype laboratory-based imagers. In this review, we discuss OCT imaging primarily of the cornea. We also highlight previous and current publications on nonclinical and clinical uses of the device to illustrate how anterior segment OCT can be used to understand corneal structure and function in health and disease. © 2008 Ethis Communications, Inc.

Simpson,T. L., Situ,P., Jones,L. W., Fonn,D. Dry eye symptoms assessed by four questionnaires. Optometry and Vision Science 2008;85,8:E692-E699. [ Show Abstract ]

PURPOSE.: To establish the relationships between commonly used questionnaires including Dry Eye Questionnaire, McMonnies Questionnaire, and Ocular Surface Disease Index, and to test the construct and face validity of the simple Subjective Evaluation of Symptom of Dryness. METHODS.: Ninety-seven non-contact lens wearing subjects were enrolled in the study and classified into either a "dry" and "non-dry" group using a single score from an initially applied subjective evaluation of symptom of dryness. The four questionnaires were then completed in a random order. The unidimensionality and accuracy of the responses was assessed using Rasch and receiver (or relative) operating characteristics curve analysis and the characteristics of and association between symptoms were compared using non-parametric statistics. RESULTS.: The responses from the Dry Eye Questionnaire, McMonnies Questionnaire, and Ocular Surface Disease Index met the Rasch analysis criterion of unidimensionality. Each test separated the symptomatic and asymptomatic groups well [all receiver (or relative) operating characteristics area-under-the-curve statistics at least 0.88] and there were significant associations between the results from each questionnaire (all Spearman ρ at least 0.64). CONCLUSIONS.: The results illustrate that different questionnaire-based instruments examining symptoms in controls and symptomatic subjects derive unidimensional data that are similar inasmuch as the overall scores are highly correlated. The data also point to the utility of a quick, three-question screening tool in dry eye research. © 2008 American Academy of Optometry.

Situ,P., Simpson,T. L., Fonn,D., Jones,L. W. Conjunctival and corneal pneumatic sensitivity is associated with signs and symptoms of ocular dryness. Investigative Ophthalmology and Visual Science 2008;49,7:2971-2976. [ Show Abstract ]

PURPOSE: To investigate the relationships of dry eye symptoms and corneal and conjunctival sensitivity to pneumatic stimulation, tear film stability, and clinical ocular surface characteristics in symptomatic and asymptomatic subjects. METHODS: Ninety-seven subjects were enrolled and grouped by a questionnaire-based single score for symptoms of ocular dryness (none to trace, non-dry group; mild to severe, symptomatic group); 43 were symptomatic and 54 were non-dry. Corneal (K) and conjunctival (C) sensitivities were measured with a computer-controlled Belmonte pneumatic (room temperature) stimulus. Symptoms were assessed according to the Ocular Surface Disease Index (OSDI). Ocular surface staining with fluorescein (FL) and lissamine green (LG), noninvasive tear film break-up time (NIBUT), and the phenol red thread test (PRT) were assessed. RESULTS: The symptomatic group showed lower K and C thresholds (P < 0.01), greater corneal FL and conjunctival LG staining, and shorter NIBUT than did the non-dry eye group (all others P < 0.05). The OSDI scores were higher in the symptomatic group (P < 0.001). K and C thresholds and NIBUT were inversely correlated with the OSDI and corneal and conjunctival staining (all P < 0.05). The K and C threshold and NIBUT (all P < 0.01) correlated positively. Step-wise multiple regression analysis showed that ocular surface sensitivity and NIBUT were significant predictors of the OSDI. CONCLUSIONS: Ocular irritation assessed with the OSDI is associated with ocular surface hyperesthesia to cooling, corneal epitheliopathy, and tear film instability. Although cause and effect are unclear, the analysis showed that altered corneal and conjunctival sensory processing and tear film attributes are essential aspects of what characterizes dry eye.

Situ,P., Simpson,T. L., Jones,L. W., Fonn,D. Conjunctival and corneal hyperesthesia in subjects with dryness symptoms. Optometry and Vision Science 2008;85,9:867-872. [ Show Abstract ]

PURPOSE.: To compare conjunctival and corneal sensitivity in noncontact lens wearing subjects with and without symptoms of ocular dryness, stratified by age and gender. METHODS.: Ninety-seven subjects were enrolled, 54 of whom were asymptomatic and 43 of whom were symptomatic of ocular dryness. A single score for the symptom of dryness was used to classify nondry eye (scores of none to trace) and dry eye symptomatic (scores of mild to severe) groups. The subjects were further stratified into "younger" (19 to 49 years) and "older" age groups (50 to 80 years). Conjunctival and corneal sensitivity of the right eye was measured at the central cornea and temporal conjunctiva, using a computer-controlled pneumatic esthesiometer with stimulus temperature set at 20°C. The ascending method of limits was used to determine the thresholds. RESULTS.: Conjunctival and corneal thresholds were significantly lower in the dry eye symptomatic than in the nondry eye group (both p 0.05). Conjunctival threshold in the nondry eye women was lower than the men (p 0.05). CONCLUSIONS.: Conjunctival and corneal sensitivity to pneumatic cool stimulation is increased in subjects with symptoms of ocular dryness. This hyperesthesia seems to be more significant in the conjunctiva. © 2008 American Academy of Optometry.

2007

Duench,S., Simpson,T., Jones,L. W., Flanagan,J. G., Fonn,D. Assessment of variation in bulbar conjunctival redness, temperature, and blood flow. Optometry and Vision Science 2007;84,6:511-516. [ Show Abstract ]

PURPOSE. To assess the diurnal variation in bulbar conjunctival redness, conjunctival temperature, and conjunctival blood flow. METHODS. Bulbar redness was quantified by CIE u' chromaticity using a SpectraScan PR650 spectrophotometer. Conjunctival temperature was measured using a Tasco-Thi 500 infrared thermometer. Measurements of conjunctival blood flow were obtained using a modified Heidelberg Retinal Flowmeter (HRF). Measurements on 10 subjects were made on a periodic basis over the day and on waking. RESULTS. For each factor measured a cyclical pattern was observed, with highest values on waking, a reduction in values towards mid-day, and then a gradual increase over the remainder of the day. There was a significant effect of time for redness, temperature, and conjunctival blood flow (p < 0.001 for all three variables), with no significant difference in the cyclical pattern between eyes being observed (p = NS). CONCLUSIONS. Diurnal bulbar redness, temperature, and conjunctival blood flow variation may be objectively quantified and all three are lowest during the middle of the day and maximal at the start of the day. This information should be considered when undertaking studies in which redness, temperature, and ocular surface blood flow are important outcome variables and time of day is a potential confounding factor. © 2007 American Academy of Optometry.

Fonn,D., Simpson,T., Woods,J., Woods,C. New technologies to assess lens-mediated effects of the cornea. Eye and Contact Lens 2007;33,6 PART 2 OF SUPPL 2:364-370. [ Show Abstract ]

Contact lenses can affect the cornea in a variety of ways. Corneal structure can be altered so that its thickness changes to involve the epithelium and the stroma. As a result, the curvature may be affected, but whether it is the front or the back surface that is affected depends on the type of lens used. If thickness increases sufficiently, corneal transparency may decrease. Contact lenses can also affect cellular structure of all layers of the cornea through mechanical trauma, hypoxia, or toxicity from solutions that are used in association with lenses. More serious complications, such as inflammation and infection, can arise. All these changes can be detected by clinicians using slitlamp biomicroscopes and keratometers if the changes are significant enough. Since the development of computers, optical instruments have become more sophisticated and have enabled the detection of subtle changes but have also facilitated more precise measurement of these conditions along with the ability to capture images of the alterations or defects. This article describes some of the newer techniques and, specifically, the application of optical coherence tomography, confocal microscopy, and esthesiometry. © 2007 Lippincott Williams & Wilkins, Inc.

Haque,S., Fonn,D., Simpson,T., Jones,L. Corneal refractive therapy with different lens materials, Part 1: Corneal, stromal, and epithelial thickness changes. Optometry and Vision Science 2007;84,4:343-348. [ Show Abstract ]

PURPOSE. To assess the corneal swelling response to two myopic correction corneal refractive therapy (CRT) lenses of varying Dk/t values, worn for a single night. Change in thickness of the total cornea, stroma, and epithelium was measured across the horizontal meridian using optical coherence tomography (OCT). METHODS. In this double-masked, randomized study, twenty subjects wore a CRT design lens in each eye, manufactured from Menicon Z (MenZ; Dk/t = 91) and Equalens II (EqII; Dk/t = 47) materials. Baseline corneal thickness was measured centrally and at four points either side of the central cornea using OCT, the night before sleeping at the Centre for Contact Lens Research. The next morning, lenses were removed, and thickness measurements were repeated 1, 3, 6, and 12 h after removal. RESULTS. On lens removal, the MenZ eye had central and paracentral corneal swelling (mean ± SD) of 4.1 ± 2.0% and 5.6 ± 2.4%, and the EqII eye had 5.8 ± 2.6% and 7.0 ± 2.6%. These values were significantly different from baseline (ReANOVA; p 0.05). Stromal swelling values on lens removal were 5.7 ± 2.2% centrally and 5.5 ± 3.0% mid-peripherally (MenZ) and 7.7 ± 3.1% centrally and 6.6 ± 2.9% mid-peripherally (EqII) (all p < 0.001 from baseline). Central stromal swelling was different between eyes at lens removal (p < 0.001). Stromal thickness in both eyes returned to baseline values within 3 h. CONCLUSION. The higher-Dk/t MenZ material caused significantly less overnight corneal and stromal swelling than the Eqll material, which reinforces the need to prescribe lenses with high Dk/t for overnight wear. Neither central epithelial thinning nor paracentral thickening are significantly affected by Dk/t. © 2007 American Academy of Optometry.

Lu,F., Simpson,T., Sorbara,L., Fonn,D. The relationship between the treatment zone diameter and visual, optical and subjective performance in Corneal Refractive Therapy™ lens wearers. Ophthalmic and Physiological Optics 2007;27,6:568-578. [ Show Abstract ]

Purpose: To investigate the stability of the treatment zone (TZ) size during Corneal Refractive Therapy (CRT™) over 4 weeks of lens wear, and to determine the relationship between TZ diameter and visual, optical and subjective performance. Methods: Twenty-three myopic subjects wore CRT™ lenses overnight and removed their lenses on awakening. Visual Acuity (VA), subjective vision, refractive error, aberrations and corneal topography were measured at baseline, immediately after lens removal on the first day and 14 h later, and these measurements were repeated on days 4, 10 and 28. The TZ including the central flattened zone (CFZ) and the annular steepened zone (ASZ) was demarcated by the change in corneal curvature from negative to positive and vice versa, using the tangential difference map from the Atlas corneal topographer. Results: After overnight CRT™ lens wear, the central cornea flattened and the mid-periphery steepened (both p < 0.001). After 4 weeks of lens wear, the CFZ (±SE) increased from 3.41 ± 0.09 mm on day 1 morning to 3.61 ± 0.07 mm on day 28 morning and the diameter of the ASZ increased from 8.17 ± 0.16 mm (day 1 morning) to 8.85 ± 0.14 mm (day 28 morning) (both p < 0.001). From day 10 onwards, the CFZ and ASZ diameter were stable in the morning (p ≥ 0.404). Throughout the day, the CFZ became smaller during the first 10 days (all p ≤ 0.022), whereas the ASZ diameter remained constant (all p ≥ 0.079). There were positive correlations between the CFZ or ASZ and residual refractive error, subjective vision and spherical aberration. The CFZ was also correlated with astigmatism and higher order aberrations, and the ASZ was positively correlated with coma (r = 0.726 to 0.961, all p ≤ 0.042). In addition, there were negative correlations between the CFZ or ASZ and total aberration and defocus and between the ASZ and VA (r = -0.707 to -0.953, all p ≤ 0.050). Conclusion: The TZ changed during the first 10 days. Its size was associated with VA, residual refractive error, aberrations and subjective vision. The concept of a TZ is a useful metric of visual, optical and subjective performance in CRT™ lens wearers. © 2007 The Authors.

Lu,F., Simpson,T., Sorbara,L., Fonn,D. Corneal Refractive Therapy™ with different lens materials, Part 2: Effect of oxygen transmissibility on corneal shape and optical characteristics. Optometry and Vision Science 2007;84,4:349-356. [ Show Abstract ]

PURPOSE. To compare the effects of two different oxygen transmissible (Dk/t) lenses on corneal shape and optical performance after one night of corneal refractive therapy (CRT®) for myopia. METHODS. Twenty myopic subjects were fit with Menicon Z (MZ) (Dk/t = 90.6, Paragon CRT® lenses) on one eye and an Equalens II (EII) CRT® lens (Dk/t = 47.2) on the contralateral eye (eye randomized). Corneal topography, refractive error and aberrations were measured before lens insertion (baseline), and the following day after overnight lens wear, on lens removal and 1, 3, 6, 12 h later. Root mean square wavefront errors were measured using 4.5 mm pupils. RESULTS. Averaged over position and time, the horizontal corneal curvature was statistically different between the MZ and EII lens-wearing eyes (p = 0.011). The central cornea flattened similarly (p = 0.886) and the mid-periphery steepened in both eyes (p = 0.061) from baseline. The EII lens-wearing eyes were steeper in the mid-periphery than the MZ eyes immediately after lens removal and at the 1-h visit (p ≤ 0.032). Central corneal flattening and mid-peripheral corneal steepening regressed over time (all p < 0.001) but did not recover to baseline by 12 h (all p < 0.004). Myopia was reduced equally by 0.84 ± 0.83 D for the MZ-lens wearing eyes and 0.84 ± 0.87 D for the EII eyes (p = 0.969). Coma increased from baseline 1.85X (0.056 ± 0.081 μm) for the MZ-lens wearing eyes and 1.72X (0.048 ± 0.084 μm) for the EII eyes (both p < 0.001). Spherical aberration increased from baseline 4.55X (0.101 ± 0.077 μm) for the MZ-lens wearing eyes and 4.31X (0.085 ± 0.076 μm) for the EII eyes (both p < 0.001), but there were no differences between the MZ and EII eyes (all p ≥ 0.308). Coma and spherical aberration did not return to baseline by 12 h (both p ≤ 0.007). CONCLUSIONS. After one night of CRT® lens wear, changes in corneal shape were slightly different, with more mid-peripheral steepening in the EII eyes compared to the MZ eyes. Change in central corneal curvature and optical performance were similar in both eyes. © 2007 American Academy of Optometry.

Lu,F., Sorbara,L., Simpson,T., Fonn,D. Corneal shape and optical performance after one night of Corneal Refractive Therapy™ for hyperopia. Optometry and Vision Science 2007;84,4:357-364. [ Show Abstract ]

PURPOSE: To investigate the corneal shape and optical performance following one night of Corneal Refractive Therapy for hyperopia (CRTH). METHODS: Twenty subjects (spherical equivalent: -2.14 +/- 2.54 D) were fit with a Paragon CRTH lens (Dk = 100) on one eye randomly. The other eye served as the control. Aberrations, refractive error, and corneal topography at various locations along the horizontal meridian were measured at baseline prior to lens insertion, and immediately after lens removal and at 1, 3, 6, 12, and 28 hours later. Root mean square wavefront errors were measured using a 4.5 mm pupil size. RESULTS: After one night of CRTH lens wear, the central cornea steepened and paracentral region flattened in the experimental eyes (p < 0.001), whereas no significant location effect was found in the control eyes (p = 0.139). Refractive error (mean +/- SE) changed by 1.23 +/- 0.21 D (p < 0.001). The defocus increased by 0.58 +/- 0.09 microm (p < 0.001). Higher-order aberrations, coma, and spherical aberrations increased by factors of 2.69, 2.58, and 4.07, respectively (all p < 0.001). Spherical aberrations shifted from positive to negative. Astigmatism did not change over time (p = 0.771). All parameters returned to baseline by 28 hours (all p > or = 0.808). Aberrations and refractive error did not change in the control eyes (all p > or = 0.082). CONCLUSIONS.: The CRTH lens steepens the central cornea and flattens the paracentral region, which alters the ametropia by inducing a myopic shift. It appears to be effective for correcting hyperopia and also is reversible.

Situ,P., Simpson,T. L., Fonn,D. Eccentric variation of corneal sensitivity to pneumatic stimulation at different temperatures and with CO2. Experimental eye research 2007;85,3:400-405. [ Show Abstract ]

The purpose was to measure corneal sensitivity at multiple corneal positions using pneumatic stimuli, at room temperature and at ocular surface temperature (with and without CO2 added), in 15 healthy participants. Sensitivity of central, mid-peripheral, and peripheral cornea was measured using a computer-controlled modified Belmonte esthesiometer to deliver pneumatic cool (air at 20 °C), mechanical (air at 50 °C), and chemical stimuli (air at 50 °C with CO2 added). The ascending method of limits and method of constant stimuli were adopted to determine the threshold to these stimuli at each location. Sensitivity across the cornea using pneumatic stimuli at different temperatures and chemical stimuli varied only slightly. These patterns of variation are different to what has been previously reported using Cochet-Bonnet esthesiometry. © 2007 Elsevier Ltd. All rights reserved.

Sorbara,L., Simpson,T., Duench,S., Schulze,M., Fonn,D. Comparison of an objective method of measuring bulbar redness to the use of traditional grading scales. Contact Lens and Anterior Eye 2007;30,1:53-59. [ Show Abstract ]

Purpose: The primary objective was to compare measures of bulbar redness objectively using a photometric method with standard grading methods. Measures of redness were made on 24 participants wearing a silicone hydrogel contact lens in one eye for overnight wear. This report compares hyperaemia after 1 week of daily wear (baseline) with redness measured after 6 months of overnight wear. Method: A new method of objectively measuring bulbar conjunctival redness was performed using the Spectrascan650® Photometer by Photo Research® under fixed illumination. Photometric measures in CIEu* chromaticity values involve the measurement of chromaticity, a physical analogue of redness, greenness and blueness in the image. This method was validated in Part 1 of the study using repeated measurements on the photographic CCLRU scale. In Part 2 of the study, the photographic grading scale (CCLRU) from 0 (none) to 100 (extreme) was used to make the comparison. Results: Part 1 indicated that the photometer provides a repeatable and reliable measure of bulbar redness (CCC = 0.989). A moderately strong and significant correlation was found between the CIEu* chromaticity values and the analogue data (R = 0.795, p = 0.000) at each measurement session (from baseline to 1 day, 1 week, and 1, 3 and 6 months of overnight wear). Conclusions: This new standardized and objective method of measuring bulbar redness has great potential to replace subjective grading scales, especially with multi-centre studies, where variability between investigators occurs. This method may also detect smaller changes between visits or between eyes. Crown Copyright © 2007.

2006

Dumbleton,K., Keir,N., Moezzi,A., Feng,Y., Jones,L., Fonn,D. Objective and subjective responses in patients refitted to daily-wear silicone hydrogel contact lenses. Optometry and Vision Science 2006;83,10:758-768. [ Show Abstract ]

PURPOSE. Silicone hydrogel (SiH) lenses offer many physiological advantages for daily wear (DW) in addition to the continuous-wear modality for which they were originally developed. The purpose of this study was to investigate the clinical performance and physiological responses in a group of successful long-term wearers of conventional hydrogel lenses when refitted with DW SiH contact lenses. METHODS. Eighty-seven successful soft lens wearers (8.4 ± 4.7 years of prior lens wear) participated in this study. Bulbar and limbal hyperemia were subjectively graded and digitally photographed for subsequent masked objective evaluation. Subjective symptoms were scored using visual analog scales. In addition, refractive error, corneal curvature, and corneal thickness were measured. All subjects were refitted with Focus Night & Day (lotrafilcon A) SiH lenses; however, to reduce the potential for bias, they were informed that they were being randomly assigned to wear either low oxygen permeability (Dk) lenses or high Dk SiH lenses and were "masked" as to their lens assignment. Subjects returned after 1 week, 1 month, and 2 months of DW, at which time all gradings, photographs, and measurements were repeated. End-of-day subjective symptoms were also graded periodically during the study. RESULTS. Ninety-three percent of subjects were successfully refitted. Both objective and subjective evaluations showed that bulbar and limbal hyperemia decreased significantly in all quadrants during the study (p < 0.001), particularly for those subjects with greater baseline hyperemia (p < 0.001). Subjects reported a concurrent reduction in end-of-day dryness and improved end-of-day comfort compared with their habitual lenses (p < 0.001). No significant changes in refractive error, tarsal papillary response, corneal curvature, or corneal thickness were found during the study. CONCLUSIONS. Hyperemia in contact lens wearers may be attributed to a number of factors, including hypoxia. Refitting existing low Dk lens wearers with SiH lenses on a DW basis can result in a decrease in hyperemia, which may be significant for some subjects and also results in improvements in symptoms of dryness and discomfort. © 2006 American Academy of Optometry.

Lu,F., Simpson,T., Fonn,D., Sorbara,L., Jones,L. Validity of pachymetric measurements by manipulating the acoustic factor of Orbscan II. Eye and Contact Lens 2006;32,2:78-83. [ Show Abstract ]

PURPOSE. To assess the validity of pachymetric measurements by examining the constancy of the acoustic factor (AF) of the Orbscan II (Orbtek, Bausch & Lomb, Rochester, NY) after overnight rigid gas-permeable (RGP) contact lens wear. METHODS. Twenty participants wore CRT (Paragon Vision Sciences, Mesa, AZ) HDS 100 contact lenses on one eye and control lenses on the contralateral eye for one night while sleeping. Another 24 participants wore CRT lenses on both eyes for one night. Central corneal thickness was measured using optical coherence tomography and Orbscan II on the night before lens use, immediately after lens removal on the following morning, and 1, 3, 6, and 12 hours later. By using optical coherence tomography as a reference, the adjusted AF was calculated by using a least squares method over time. RESULTS. The adjusted AF depended on the corneal thickness in normally hydrated corneas. The adjusted AF and the percentage change of the adjusted AF varied before and after overnight lens wear. There was a strong and significant correlation between the corneal swelling and the percentage change of the adjusted AF (all r at least 0.91, P<0.05). CONCLUSIONS. The adjusted AF is a variable, not a constant. The AF is a function of the corneal thickness and its alteration with, for example, corneal swelling. The validity of the adjusted Orbscan II pachymetric measures using a single AF is untenable. © 2006 Lippincott Williams & Wilkins, Inc.

Moezzi,A. M., Fonn,D., Simpson,T. L. Overnight corneal swelling with silicone hydrogel contact lenses with high oxygen transmissibility. Eye and Contact Lens 2006;32,6:277-280. [ Show Abstract ]

PURPOSE. To compare central corneal swelling after 8 hours of sleep in eyes wearing 2 different silicone hydrogel lenses with high oxygen transmissibility. METHODS. Twenty neophyte subjects were randomly assigned to wear a comfilcon A lens (CooperVision Inc) in one eye and a lotrafilcon A lens (CIBA Vision) in the contralateral eye for an 8-hour overnight period. The study was repeated with another 20 neophyte subjects wearing comfilcon A in one eye only and no lens in the contralateral control eye. Central corneal thickness was measured with optical pachometry before lens insertion, immediately after lens removal on waking, at 20 and 40 minutes, 1 hour, 2 hours and 3 hours. RESULTS. There was no significant difference between the amount of overnight central corneal swelling induced by the 2 lenses (4.1% ± 1.9% with comfilcon A vs. 4.0% ± 1.7% with lotrafilcon A; P>0.05). The swelling of the comfilcon A lens-wearing eyes was significantly higher than that found in the non-lens-wearing contralateral eyes (4.5% ± 2.1% vs. 3.0% ± 1.7%; P<0.05). CONCLUSIONS. The same amount of overnight corneal swelling was induced by the 2 study lenses. The higher overnight swelling observed with the comfilcon A lenses compared to the non-lens-wearing eyes is similar to that reported in the literature for studies using lotrafilcon A lenses. © 2006 Lippincott Williams & Wilkins, Inc.

2005

Fonn,D., Bruce,A. S. A review of the Holden-Mertz criteria for critical oxygen transmission. Eye and Contact Lens 2005;31,6:247-251. [ Show Abstract ]

Purpose. Holden and Mertz established the foundations for the new generation of silicone hydrogel contact lenses for daily and extended wear in 1984. Absence of lens-induced corneal swelling was their premise and although this was possible with daily wear, the goal with extended wear seemed almost impossible because of the limitation of hydrogel materials. Experience with extended and daily wear of disposable contact lenses during the last 2 decades and, more recently, with silicone hydrogels has led to the reconsideration of the validity of the findings of Holden and Mertz. Results. A pivotal influence on the Holden and Mertz critical Dk/t value for closed-eye lens wear was exerted by two numbers: the no-lens wear corneal edema level (4%) and the silicone lens data point (Dk/t of 182 × 10-9, closed-eye edema level of 2.6%). Subsequent publications appear to give a more accurate assessment of the no-lens closed-eye corneal edema level, and there are also more recent measurements of silicone hydrogel lens Dk/t and corneal edema responses. Conclusions. It now appears that the Holden and Mertz criteria for extended-wear critical Dk/t should be revised upwards to at least 125 × 10 -9. © 2005 Contact Lens Association of Ophthalmologists, Inc.

Fonn,D., Sweeney,D., Holden,B. A., Cavanagh,D. Corneal oxygen deficiency. Eye and Contact Lens 2005;31,1:23-27. [ Show Abstract ]

Objectives. To compare the ocular effects of low Dk hydrogel and high Dk silicone hydrogel contact lenses. Methods. A review of recent literature was conducted to determine the effects of wearing low and high Dk soft lenses on corneal swelling, vascular response, refractive error and the corneal epithelium. Results. High Dk silicone hydrogel contact lenses became available for research and clinical practice almost 10 and 5 years ago respectively. During that time many studies have been conducted and it has been demonstrated repeatedly how much improvement there has been to the physiological response of the eye particularly when wearing the lenses on an overnight basis. Conclusions. Although silicone hydrogels only constitute about 2% of current wearers, their positive effects on the eye compared with low Dk hydrogel lenses should make them the most dominant lenses in the near future. © 2005 Contact Lens Association of Ophthalmologists, Inc.

Sorbara,L., Fonn,D., Simpson,T., Lu,F., Kort,R. Reduction of myopia from corneal refractive therapy. Optometry and Vision Science 2005;82,6:512-518. [ Show Abstract ]

Purpose. The purpose of the study was to monitor the efficacy of corneal refractive therapy (CRT) lenses to reduce myopia over a 4-week period. Refractive error, keratometry, high and low contrast acuity, and subjective vision after 28 days of using CRT contact lenses were measured. Methods. Twenty-three myopes wore CRT HDS lenses, Dk = 100. The Nikon autokefractor/keratometer was used to measure the refractive error and keratometric changes. Visual acuity was measured using computerized high and low contrast charts and the subjects completed visual analog scales characterizing their vision on a daily basis. Measurements were performed at baseline (before lens insertion before sleep), immediately after lens removal the next morning and at 1, 3, 7, and 14 hours after eye opening. Measurements were made on the days following 1, 4, 10, and 28 nights of lens wear. After 72 hours of no lens wear, these parameters were again measured to assess corneal recovery. Results. The pretreatment manifest refraction (mean of OD and OS ± standard deviation [SD]) was -2.72 DS ± 1.06 and -0.55 DC ± 0.40. Myopic spherical equivalent refractive error (± SD) decreased by 1.30 DS ± 0.53 (range 0-3 D) immediately after lens removal on day 1 and by 2.59 DS ± 0.77 by day 28 (range 1.25-3.88 D). The cylinder remained unchanged. Uncorrected visual acuity improved by 5 lines after one night and reached 0.00 LogMAR (6/6) by day 4. Visual acuity was maintained throughout the day by day 10. The day and time effect of the spherical equivalent change and the central corneal radius of curvature were statistically significant (p < 0.01) up to day 10 and remained the same until day 28. Central (autokeratometer) Ks flattened by 1.28 D ± 1.35 after one night and 2.33 D ± 1.30 by day 28. The subjective vision improved significantly from day 1 to day 28 (p < 0.01) and was maintained throughout the day from day 4 to day 28 (p < 0.01). All measures did not recover completely to baseline after 72 hours of no lens wear. Conclusions. CRT lenses significantly reduced myopia, improved visual acuity and subjective vision, and flattened central corneal curvature. Maximal effect was achieved after 10 days and was maintained for the rest of the study period. Copyright © 2005 American Academy of Optometry.

2004

Haque,S., Fonn,D., Simpson,T., Jones,L. Corneal and epithelial thickness changes after 4 weeks of overnight corneal refractive therapy lens wear, measured with optical coherence tomography. Eye and Contact Lens 2004;30,4:189-193. [ Show Abstract ]

Purpose. To investigate thickness changes of the total cornea and epithelium across the horizontal corneal meridian after 4 weeks of overnight corneal refractive therapy (CRT) rigid contact lens (Paragon Vision Sciences, Mesa, AZ) wear. Methods. Thirty subjects were fitted with CRT contact lenses (Dk/t = 67), which were worn overnight for 4 weeks. Corneal thickness was measured at nine locations along the horizontal meridian by using optical coherence tomography (OCT) before lens insertion in the evening. Corneal thickness was measured the next morning immediately after lens removal and 1, 3, 7, and 14 hours later. This was repeated on days 4, 10, and 28 of the study and then 3 days after discontinuing lens wear. Results. Twenty-three subjects completed the study. At lens removal on day 1, the central and paracentral cornea swelled by 4.9% and 6.2%, respectively (both P = 0.000). The central epithelium thinned by 7.3%, and the mid peripheral epithelium thickened by 13% (both P = 0.000). Corneal swelling recovered throughout the day, with most of the deswelling taking place within the first 3 hours after lens removal. Maximal central epithelial thinning reached 13.5% by day 4. Three days after the study completion, corneal and epithelial thickness had recovered to baseline values. Conclusions. This study shows that CRT lenses induce differential overnight swelling across the cornea, with rapid deswelling during the day. Central epithelial thinning and paracentral thickening occurs, with recovery 3 days after discontinuation of lens wear. © 2004 Contact Lens Association of Ophthalmologists, Inc.

Moezzi,A. M., Fonn,D., Simpson,T. L., Sorbara,L. Contact lens-induced corneal swelling and surface changes measured with the Orbscan II corneal topographer. Optometry and Vision Science 2004;81,3:189-193. [ Show Abstract ]

Purpose. The purpose of this study was to measure central and topographical corneal swelling in response to contact lens wear and eye closure, to determine whether the swelling induced by soft and polymethyl methacrylate (PMMA) lenses is different, and to determine whether the anterior and/or posterior corneal shape alters with corneal swelling. Methods. An Orbscan II corneal topographer was used to measure corneal swelling and the shape of the anterior and posterior corneal surfaces of 16 neophytes before and after wearing soft and PMMA contact lenses with near-zero oxygen transmissibility. The lens-wearing eye was patched for 3 h. Results. The mean 15.1% ± 3.8% (±SD) central corneal swelling with soft lenses was significantly > 12.6% ± 4.1% with PMMA lenses. Topographical corneal swelling was significantly greater with soft vs. PMMA lenses. However, the difference between central and peripheral corneal swelling was much greater with PMMA lenses. With both lenses, the cornea swelled significantly more in the center than the periphery. The anterior best-fit sphere radius remained unchanged in response to soft lenses (0.00 ± 0.04 mm) and steepened slightly but significantly with PMMA lenses (-0.04. ± 0.05 mm). The posterior best-fit sphere radius flattened significantly with both lenses (0.12 ± 0.07 mm with soft and 0.14 ± 0.08 mm with PMMA lenses). Conclusions. Corneal swelling (greater centrally than peripherally) flattens the posterior surface of the cornea and is independent of lens type. Although the anterior best-fit sphere radius steepened with PMMA, the magnitude is probably clinically unimportant. Both lens types produced greater central vs. peripheral corneal swelling. However, the soft lens induced significantly greater overall swelling than PMMA. Because their oxygen transmission was the same, these results suggest that there is lateral diffusion of oxygen from the peripheral area of the cornea (that is not covered by the lens) toward the center.

Sorbara,L., Simpson,T., Vaccari,S., Jones,L., Fonn,D. Tear turnover rate is reduced in patients with symptomatic dry eye. Contact Lens and Anterior Eye 2004;27,1:15-20. [ Show Abstract ]

Purpose: Tear turnover rate (TTR) is defined as the percent decrease of fluorescein concentration in the tears per minute after the instillation of fluorescein. The purpose of this study was to examine differences in TTR in a sample with symptoms of dry eye and an asymptomatic control sample using the Fluorotron Master™ Fluorophotometer. Methods: TTR was measured using the OcuMetrics Fluorotron Master™. It measures the decay of the fluorescence of high molecular weight fluorescein FITC Dextran instilled into the tear film. Twenty participants (post-menopausal women) were enrolled in the study (10 asymptomatic (age 64.7±6.99) and 10 symptomatic (age 61.5±7.98)). Participants were grouped according to either a positive (symptomatic) or negative (asymptomatic) McMonnies Dry Eye Questionnaire, i.e., an indication of self-reported ocular dryness and the use of rewetting/lubricating drops (questions 4 and 5). TTR was measured in the afternoon only. Measurements were made on the right eye with a controlled blink rate (15 blinks/min), for up to 30 min, post-insertion of 2 μl of 2% FITC Dextran (MW 9500). The scan data were used to construct a graph of log fluorescein concentration (ng/ml) as a function of time and the TTR calculated (%/min=(1-ln (slope))×100). Results: There was a significant difference in the TTR between symptomatic and asymptomatic subjects. Mean TTR (symptomatic) was 4.89±2.74%/min (range, 2.04-11.81) and mean TTR (asymptomatic) was 11.85±3.31%/min (range, 5.76-16.45) (P<0.0001). Conclusions: Fluorophotometry may be used to demonstrate differences in the tear turnover rate in this post-menopausal group of women, with patients experiencing symptoms of dry eye having a lower TTR than the normals. © 2003 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

2003

Wang,J., Fonn,D., Simpson,T. L. Topographical thickness of the epithelium and total cornea after hydrogel and PMMA contact lens wear with eye closure. Investigative Ophthalmology and Visual Science 2003;44,3:1070-1074. [ Show Abstract ]

PURPOSE. To determine changes in topographical thickness of the epithelium and total cornea after hydrogel (2-hydroxyethyl methacrylate; HEMA or soft lens) and PMMA rigid contact lens wear with eyes closed, as measured by optical coherence tomography (OCT). METHODS. Epithelial and total corneal thickness in 18 neophyte eyes was measured with OCT at intervals of 10° across a 10-mm zone of the horizontal meridian of the cornea, before and after 3 hours of soft and rigid contact lens wear with the eye closed. These measurements were repeated 20 minutes after removal of the lenses. RESULTS. Lens type, time, and location were found to be significant main influences (P < 0.0001) on corneal swelling in patched eyes, by three-way ANOVA, and there was a significant three-way interaction among lens type, time, and location (F(16,272) = 1.78, P = 0.033). However, there was no significant main effect and interaction of epithelial thickness (F(16, 272) = 0.33, P = 0.99). Immediately after removal of the lenses, total corneal thickness in the horizontal meridian was significantly greater with both soft and PMMA lenses (P < 0.001) at each location with each lens, compared with the baseline measurements. With both lenses, the increase in actual thickness and percentage of corneal swelling at the center was greater than at each peripheral point (excluding the first 10° points; P < 0.005). HEMA lenses caused greater corneal swelling than the PMMA lenses at each location immediately after removal of the lenses (P < 0.005). CONCLUSIONS. This study shows that corneal swelling is dependent on lens type and corneal location when eyes are closed, but epithelial thickness across the horizontal corneal meridian does not change during lens wear with eyes closed. OCT is an efficient method of measuring topographical corneal and epithelial thickness in response to contact lens wear.

Wang,J., Fonn,D., Simpson,T. L., Jones,L. Precorneal and pre- and postlens tear film thickness measured indirectly with optical coherence tomography. Investigative Ophthalmology and Visual Science 2003;44,6:2524-2528. [ Show Abstract ]

PURPOSE. To demonstrate the feasibility of indirectly measuring the precorneal tear film thickness and pre- and postlens tear film (PLTF) thickness using optical coherence tomography (OCT). METHODS. Central corneal thickness (C1) which includes the tear film (T) of both eyes of 40 non-contact lens wearers was measured using OCT after calibration. The mean age of the 40 subjects was 31.2 ± 9.3 years with a mean horizontal K-reading of 7.87 mm. Rigid contact lenses with base curves 0.3- to 0.5-mm steeper than the flattest K of the eye were fitted to measure real corneal thickness (C2), independently of the postlens tear film. T was calculated by T = C1 - C2. To measure pre- and postlens tear film thickness, Focus Night & Day and Acuvue lenses (Vistakon, Johnson & Johnson Vision Care, Jacksonville, FL) were fitted on both eyes. Central soft lens thickness (L1), which includes the prelens tear film (P), was measured by OCT in situ and in saline in a wet cell (L2). P was calculated by P = L1 - L2. Thickness of the central cornea plus the postlens tear film (C3) was measured during lens wearing. Postlens tear film (PLTF) was calculated by PLTF = C3 - C2. RESULTS. The mean ± SD precorneal tear film thickness was 3.3 ± 1.5 μm (range, 0-6.9) before lens insertion and 4.7 ± 2.3 μm (range, 0.7-11.0) after lens fitting, which was significantly thicker (paired t-test: P < 0.01). The prelens tear film thickness was 3.9 ± 2.6 and 3.6 ± 2.1 μm (mean ± SD; paired t-test: P = 0.52) and the postlens tear film thickness was 4.5 ± 2.3 and 4.7 ± 3.1 μm (paired t-test: P = 0.08) on and under Focus Night & Day and Acuvue lenses, respectively. Post hoc tests showed that precorneal (baseline) and prelens tear films were equivalent, and each was different (thinner; Tukey honestly significant difference P < 0.05) from the postlens tear film. CONCLUSIONS. OCT can noninvasively measure the thickness of the precorneal and prelens tear film as well as the postlens tear film. The thickness of the normal precorneal tear film is approximately 3 μm and becomes thicker after lens fitting. The postlens tear film is thicker than the precorneal and prelens tear films with soft contact lenses. The thickness of both preand postlens tear films appears to be independent of the investigated lens types.

Du Toit,R., Vega,J. A., Fonn,D., Simpson,T. Diurnal variation of corneal sensitivity and thickness. Cornea 2003;22,3:205-209. [ Show Abstract ]

Purpose. To measure the diurnal variation of central corneal sensitivity and thickness over 24 hours. Methods. A noncontact pneumatic esthesiometer to measure central corneal sensitivity and an optical pachymeter to measure central corneal thickness were used on 20 noncontact lens wearers. These measurements were performed at 22:00 before 8 hours of sleep and on the following day on eye opening and at hourly intervals between 7:00 and 22:00. Results. Central corneal sensitivity varied by 35% over the 24 hours. Sensitivity was significantly lower by 17.1 ± 2.1% on eye opening and recovered to the level of the previous night after 4 hours. Corneal sensitivity continued to increase throughout the day but was not significantly higher. Central corneal thickness varied by 3.9% over the 24 hours. The mean overnight corneal swelling was 2.9 ± 0.31%, and 2 hours after eye opening, the cornea had deswelled to the same thickness as the previous night. The cornea thinned further throughout the day, but there were no statistically significant differences between the values after 14:00. There was a high correlation between corneal sensitivity and thickness over time (r = 0.8; p < 0.05). Discussion. Corneal sensitivity correlated with corneal thickness: both were higher on awakening and then decreased and remained below the levels measured the previous night. This may be due to physiological and/or environmental factors. The lack of significant differences between the values after 14:00 suggests that baseline may be measured at any time from 7 hours after eye opening.

Fonn,D., Dumbleton,K. Dryness and discomfort with silicone hydrogel contact lenses.. Eye & contact lens 2003;29,1 Suppl:S101-104; discussion S115-118, S192-194. [ Show Abstract ]

PURPOSE: The purpose of this study was to determine whether symptoms of dryness and discomfort are experienced differently with silicone hydrogel lenses compared to conventional hydrogels, in symptomatic and asymptomatic subjects. METHODS: Thirty-nine symptomatic and asymptomatic subjects wore four types of lenses: Focus NIGHT & DAY (CIBA Vision), Focus DAILIES (CIBA Vision), ACUVUE 2 (Johnson & Johnson Visioncare) and Proclear Compatibles (CooperVision) contralaterally for 7 hours and rated comfort and dryness on a zero-to-100 point visual analog scale at 0, 1, 3, 5 and 7 hours. RESULTS: In both groups, no lens differences were found for comfort and dryness, but the comfort and dryness ratings of the symptomatic group decreased significantly (became worse) over the 7-hour period. CONCLUSIONS: These results demonstrate that dryness and comfort is the same over time with silicone hydrogel as with the other three lenses.

Situ,P., Du Toit,R., Fonn,D., Simpson,T. Successful monovision contact lens wearers refitted with bifocal contact lenses. Eye and Contact Lens 2003;29,3:181-184. [ Show Abstract ]

Purpose. Should successful monovision contact lens wearers be refitted with bifocal lenses? Methods. Fifty current monovision lens wearers were fitted with ACUVUE Bifocal contact lenses (Johnson & Johnson Vision Care, Jacksonville, FL). Visual function and subjective vision ratings were assessed with habitual monovision lenses at the first visit and then were repeated at the end of 6 months while wearing bifocal lenses. Lens preference was determined at the end of the 6-month study, and the subjects were called 1 year later to repeat the lens preference questionnaire. Results. Forty (80%) subjects completed the 6-month study; nine discontinued for visual reasons. At the end of 6 months of wear, 68% preferred bifocal lenses and 25% preferred monovision. Of the subjects who were contacted a year later, 53% were still wearing bifocal lenses. High-contrast visual acuity and letter contrast sensitivity at distance was the same for monovision and bifocal lenses, but low-contrast acuity was better with monovision. Intermediate low- and high-contrast acuity and 3-meter and near stereoscopic acuity were better with bifocal lenses. Near high- and low-contrast acuity were better with monovision. All subjective ratings, except near vision in poor lighting, were significantly greater with bifocal lenses. Conclusions. It is possible to refit successful monovision lens wearers with simultaneous vision bifocal lenses, and these lenses should be considered as an alternative method for the correction of presbyopia. In addition, subjective responses to bifocal lenses may not be reflective of visual function measurements. © 2003 Contact Lens Association of Ophthalmologists, Inc.

2002

Wang,J., Fonn,D., Simpson,T. L., Jones,L. Relation between optical coherence tomography and optical pachymetry measurements of corneal swelling induced by hypoxia. American Journal of Ophthalmology 2002;134,1:93-98. [ Show Abstract ]

PURPOSE: To determine the relation between optical coherence tomography (OCT) and optical pachymetry (OP) measurements of corneal swelling induced by hypoxia. DESIGN: Experimental study. METHODS: One randomly selected eye of 20 noncontact lens wearers (10 males and 10 females, age 35.6 ± 9.6 years) was patched during 3 hours of soft contact lens (SCL) wear while the contralateral eye acted as control. Central corneal thickness of both eyes was measured before and after SCL wear using OCT and OP in randomized order. RESULTS: Baseline central corneal thickness was 523.6 ± 33.0 μm (mean ± standard deviation [SD]) measured with OCT and 490.6 ± 25.5 μm with OP. Immediately after contact lens removal, corneal thickness measured with OCT increased by 13.8 ± 2.3% compared with 12.1 ± 1.8% (paired t test: P < .001) measured with OP. Thereafter, corneal thickness decreased at the rate of 5.6% per hour for OCT and 5.4% per hour for OP. The difference in thickness between instruments before lens insertion, which was 33 μm compared with the difference after lens removal (edematous cornea), which ranged from 46 to 41 μm. The difference between instruments decreased during the corneal deswelling period after lens removal. The correlation coefficient between OCT and OP was 0.914 before lens insertion and 0.932 after lens removal. CONCLUSION: This study has demonstrated the difference of corneal thickness measured with OCT and OP. Although both instruments are correlated highly in all conditions tested, OCT may overestimate corneal thickness in normal and edematous corneas. © 2002 by Elsevier Science Inc. All rights reserved.

Wang,J., Fonn,D., Simpson,T. L., Jones,L. The measurement of corneal epithelial thickness in response to hypoxia using optical coherence tomography. American Journal of Ophthalmology 2002;133,3:315-319. [ Show Abstract ]

PURPOSE: To determine if corneal epithelial thickness increases in association with corneal edema induced by wearing soft contact lenses during eye closure. DESIGN: Experimental study. METHODS: One eye (randomly selected) of twenty noncontact lens wearers (10 males and 10 females, age 35.6 ± 9.6 years) was patched during 3 hours of soft contact lens (SCL) wear and the contralateral eye acted as a control. Corneal and epithelial thickness of both eyes was measured before and after SCL wear using optical coherence tomography (OCT). RESULTS: Immediately after contact lens removal, total corneal thickness was increased significantly by 13.8 ± 2.3% (mean ± SD) compared with baseline (P .05, paired t test). Immediately after contact lens removal, corneal epithelial thickness was increased by 1.7 ± 4.8%, but this change was not statistically significant (P > .05, paired t test). Following contact lens removal, epithelial thickness changed significantly (Repeated measure analysis of variance [Re-ANOVA]: F(7,133) = 4.91, pH-F < 0.001) over the next 100 minutes with thinning recorded at 60, 80, and 100 minutes (P < .05, paired t test). There was no significant change over time in epithelial thickness of the control eyes (Re-ANOVA: F(4, 76) = 0.91, pH-F = 0.464). CONCLUSION: OCT demonstrated that corneal epithelial thickness does not increase in response to hypoxia from SCL wear and eye closure, in contrast to a significant increase in total corneal thickness. © 2002 by Elsevier Science Inc. All rights reserved.

Du Toit,R., Pritchard,N., Heffernan,S., Simpson,T., Fonn,D. A comparison of three different scales for rating contact lens handling. Optometry and Vision Science 2002;79,5:313-320. [ Show Abstract ]

Purpose. To compare the validity, responsiveness, and reliability of three subjective rating scales applied to soft contact lens (SCL) handling. Methods. Fifty-four adapted SCL wearers handled three different types of lenses on two occasions and rated the handling with each scale: visual analogue scales (VAS), 20-interval visual analogue scales with descriptors (VAD) and Likert rating scales with five intervals (LRS). Results. There were significant differences between the scales (p < 0.01) and between the subjective ratings of lens handling (p < 0.001). VAS showed the least variability, exhibited the highest construct validity, were the most responsive, and were the most reliable: interclass correlations (0.63), coefficient of repeatability (27.5), and correlation between test and retest (Spearman r = 0.65, [all p < 0.05]). Higher repeatability, because of the fewer intervals of LRS, was not demonstrated and, generally, LRS was the least satisfactory scale. Handling was rated as easiest using VAD and most difficult using LRS. Conclusions. Although all three scales can be used to provide measures of lens handling, VAS may provide a simple and repeatable tool for measuring subjective responses.

Dumbleton,K. A., Chalmers,R. L., McNally,J., Bayer,S., Fonn,D. Effect of lens base curve on subjective comfort and assessment of fit with silicone hydrogel continuous wear contact lenses. Optometry and Vision Science 2002;79,10:633-637. [ Show Abstract ]

Purpose. To study the effect of base curve on subjective comfort of silicone hydrogel extended wear lenses. Methods. Ninety-five subjects were first trial fitted with 8.6-mm base curve lotrafilcon A (Focus Night & Day) lenses and then with 8.4-mm lenses only if poor subjective comfort or poor fit was present. Comfort and fit were assessed after 15 min. Subjects with discomfort or signs of poor fit were then trial fitted with 8.4-mm lenses. Results. Of 190 eyes, 74.2% were fitted with 8.6-mm lenses, and 23.7% required 8.4-mm lenses. Two (2.1%) subjects could not be fitted with either base curve. Mean steep keratometry (K) reading for eyes dispensed with 8.6-mm lenses was 43.88 D and 45.56 D for eyes dispensed in the 8.4-mm lenses (p < 0.001). Conclusions. A clinically useful criterion showing the need for 8.4-mm lenses was steep K of ≥45.50 D; 77% of these eyes required the steeper lens for good comfort and fit. Subjective discomfort with 8.6-mm lenses was also a useful signal for the need of a steeper lens; mean comfort scores for those subjects rose from 6.33 with 8.6-mm lenses to 9.44 with the 8.4-mm lenses for eyes requiring the steeper lens (p < 0.001).

Fonn,D., MacDonald,K. E., Richter,D., Pritchard,N. The ocular response to extended wear of a high Dk silicone hydrogel contact lens. Clinical and Experimental Optometry 2002;85,3:176-182. [ Show Abstract ]

Purpose: A four-month extended wear clinical trial was conducted to compare the ocular effects of a high Dk Balafilcon A silicone hydrogel lens and a low Dk HEMA 38.6 per cent H2Osoft lens. Method: Twenty-four subjects who were adapted to daily wear of soft lenses wore a high Dk lens in one eye and a low Dk HEMA lens in the other eye for four months on an extended wear basis after one week of daily wear. Thirteen progress evaluations were conducted using standard clinical procedures. Results: Eighteen subjects (75 per cent) completed the study. The high Dk lens induced significantly less bulbar and limbal injection and corneal vascularisation than the low Dk HEMA lens (p < 0.05). Epithelial microcysts were observed only in the eyes wearing the low Dk lens. A significant increase in myopia was found in the eyes wearing the low Dk HEMA lens (mean = 0.50 D, p < 0.01) compared to the insignificant myopic increase of 0.06 D in the eyes wearing the high Dk lens. Three subjects developed small infiltrates in the high Dk lens wearing eyes and significantly more post-lens debris was observed under the high Dk lens. Six subjects developed papillary conjunctivitis in the eye wearing silicone hydrogel lenses but only two of those were discontinued from the study. Conclusion: No hypoxia-related effects were observed with extended wear of the high Dk Balafilcon A silicone hydrogel lens.

2001

Du Toit,R., Simpson,T. L., Fonn,D., Chalmers,R. L. Recovery from hyperemia after overnight wear of low and high transmissibility hydrogel lenses. Current eye research 2001;22,1:68-73. [ Show Abstract ]

Purpose. To measure the limbal vascular response after 8 hours of eye closure while wearing high and low permeability lenses compared to control eyes without lenses. Method. Twenty neophyte participants wore lotrafilcon A silicone hydrogel lenses (HDk; Dk = 140) or etafilcon A hydrogel lenses (LDk; Dk = 18). On two different nights the lenses were randomly worn for 8 hours during sleep in the right eyes only. Left eyes were non-lens wearing controls. Biomicroscopic images of the temporal limbal area were videotaped at baseline, on eye opening and every 20 minutes for 3 hours. A masked observer graded digitized images of the limbal area. Results. On waking and after lens removal there were no differences in hyperemia between the HDk and LDk lens wearing eyes. There were also no differences at any time between the HDk lens wearing eyes and their control eyes (p > 0.05). On waking the eyes wearing the LDk lens were more hyperemic compared to baseline (p < 0.001) and compared to their control eyes at 20 (p < 0.001) and 180 minutes (p = 0.01), indicating slower recovery from hyperemia. The HDk lens wearing eyes recovered to their baseline levels by 180 minutes (p = 0.99), compared to the LDk lens wearing eyes, which had not recovered to baseline levels by 180 minutes (p = 0.04). Conclusion. The reduction in hyperemia over time of the HDk lens wearing eyes was the same as the controls. The LDk lens wearing eyes were more hyperemic than the controls on waking and the reduction in hyperemia over time was slower. This suggests that the slower recovery from hyperemia may be affected by the lower oxygen transmissibility of the LDk lens.

Du Toit,R., Situ,P., Simpson,T., Fonn,D. The effects of six months of contact lens wear on the tear film, ocular surfaces, and symptoms of presbyopes. Optometry and Vision Science 2001;78,6:455-462. [ Show Abstract ]

Purpose. To assess the tear film, ocular surfaces, and symptoms of ocular discomfort in a presbyopic population before and after contact lens wear. Methods. A total of 150 presbyopes (49% were previous soft contact lens wearers) participated in a clinical trial in which they wore either monovision (single vision Acuvue lenses) or Acuvue Bifocal contact lenses. Clinical measurements of tear film, biomicroscopy, and corneal sensitivity as well as subjective ratings using the Dry Eye Questionnaire were collected at the initial visit and repeated after 6 months. Comparisons were made between age groups (40 to 51 years and 52 to 71 years) and genders before and after contact lens wear. Associations between objective and subjective tests were sought. Results. After 6 months of contact lens wear, clinical signs had worsened by less than one-half of a grade, and tear break up time (TBUT) worsened by 3 s. Only TBUT was lower for the older age group. Females had less bulbar hyperemia, more sensitive eyes, more lissamine green staining, and lower TBUT and phenol red thread measurements (all p lt; 0.04). Twenty-eight percent experienced dryness before contact lens wear, but this figure increased to 68% when wearing contact lenses. There were no age differences, but almost twice as many females as males reported dryness. Reporting symptoms of dryness was associated with gender, corneal sensitivity, and type of corneal staining. Conclusions. These results provide a representation of the ocular surface condition and symptoms of ocular discomfort in the middle-aged population and seem similar to reports of younger populations. Wearing contact lenses seems to influence dry eye symptoms more than age or gender. Therefore, presbyopes should not be excluded from consideration for contact lens fitting.

Dumbleton,K. A., Chalmers,R. L., Richter,D. B., Fonn,D. Vascular response to extended wear of hydrogel lenses with high and low oxygen permeability. Optometry and Vision Science 2001;78,3:147-151. [ Show Abstract ]

Purpose. The purpose of this study was to determine the impact of extended wear of high and low oxygen permeability (Dk) lenses on the development or resolution of limbal hyperemia and corneal neovascularization in a randomized prospective clinical trial. Methods. Adapted daily-wear contact lens wearers were randomly assigned to one of two groups. The low-Dk group (N = 23) wore etafilcon A lenses (Dk/t = 40) for up to 7 days and 6 nights, and the high-Dk group (N = 39) wore lotrafilcon A lenses (Dk/t = 175) for up to 30 days and nights. Limbal hyperemia and neovascularization were assessed and graded during 9 months of extended wear. A stratified analysis to determine how change in ocular redness depended on initial presentation was also conducted. Results. On a 0 to 100 scale, extended wear of low-Dk lenses resulted in a 16-point increase in limbal hyperemia (p < 0.0001); no significant change occurred with the high-Dk lenses. The difference was greatest for low-Dk participants who initially presented with lower levels of hyperemia (N = 18). There was a slight resolution of redness in participants who initially presented with higher levels of hyperemia (N = 10) after wearing the high-Dk lenses. Neovascularization increased by an average of 0.5 on a scale of 0 to 4 in low-Dk lens wearers (p < 0.0001) but remained unchanged in the high-Dk lens wearers. The increase was most marked for the low-Dk group with lower levels of neovascularization at baseline. Conclusions. Subjects who wore lenses with higher oxygen permeability for 9 months of extended wear exhibited a lower vascular response of the ocular surface compared with subjects who wore lenses of lower oxygen permeability for the same period. This result was found both for the surface limbal vessels and in the deeper neovascular stromal vessels. Moderate neovascularization also developed after 3 months of extended wear of low-Dk hydrogels, whereas high-Dk lenses caused no neovascularization.

2000

Chong,T., Simpson,T., Fonn,D. The repeatability of discrete and continuous anterior segment grading scales. Optometry and Vision Science 2000;77,5:244-251. [ Show Abstract ]

Purpose: To investigate the repeatability of three anterior segment clinical grading scales: 1) verbal descriptors scale (VDS), 2) photographic matching scale (PS), and 3) continuous matching scale (CS). Methods: Five optometrists graded 30 slides each of 3-9-o'clock staining, bulbar redness, and palpebral conjunctival roughness twice, separated by at least a day. VDS and PS were five-point scales (0-4.) with half grades permitted. The CS was a 5-second, 240-frame video movie generated using morphing software. PS and CS grading was done with references presented on a computer screen. Results: Averaged across observers, the test-retest intraclass correlation, correlation coefficient of concordance, and Pearson's r ranged from 0.95 to 0.99 (all p < 0.001). Coefficients of repeatability using CS to grade all three ocular conditions ranged between 0.31 and 0.49. The corresponding PS and VDS coefficients of repeatability ranged between 0.37 and 0.49; PS generally had better repeatability than VDS. Conclusions: Each of the clinical grading scales was reliable. The coefficients of repeatability showed that bulbar redness and palpebral conjunctival roughness were graded with higher precision using CS.

Dumbleton,K., Jones,L., Chalmers,R., Williams-Lyn,D., Fonn,D. Clinical characterization of spherical post-lens debris associated with lotrafilcon high-DK silicone lenses. CLAO Journal 2000;26,4:186-192. [ Show Abstract ]

Purpose: Experience with high Dk silicone hydrogel lenses has revealed post-lens debris, which is characterized by the appearance of spherical, translucent particles referred to as 'mucin balls.' The objectives of this analysis were to characterize the presence of mucin balls, determine whether any ocular characteristic predicts the development of mucin ball debris, and determine whether there is any association between mucin balls and the ocular response to contact lens wear. Methods: Ninety-two subjects wore lotrafilcon A lenses on an extended wear basis for up to 30 nights and were followed for 6 months. Mucin balls were graded on a 0 to 4 scale at three visits. Subjective ratings and biomicroscopic appearance were recorded at all visits. Results: Mucin balls were observed in 70% of subjects at one or more visits, and 29% of subjects at all three visits. There was no change in the mean grade of mucin balls over time. Mucin balls were graded > 1 in 20% of eyes, > 2 in 6% of eyes, and > 3 in 2% of eyes. Subjects who exhibited mucin balls at each clinical visit had significantly steeper keratometry readings along the flatter meridian (44.3 D) than those who never exhibited mucin balls (42.9 D, P<0.0001). The percentage of subjects who 'never' use lubricating drops was higher in the subjects with mucin balls (P=0.0014). No association was found between mucin ball observation and biomicroscopic appearance, inflammatory responses, or subjective responses. Conclusions: The presence of mucin balls does not appear to be detrimental to contact lens wear. Eyes with steeper corneal curvature were significantly more likely to present with mucin ball debris, indicating they may be a function of lens fit. Clinical factors that may be modified in order to menage the more severe presentation of mucin balls are the use of lubricating drops and the number of nights extended wear schedule.

Pritchard,N., Jones,L., Dumbleton,K., Fonn,D. Epithelial inclusions in association with mucin ball development in high-oxygen permeability hydrogel lenses. Optometry and Vision Science 2000;77,2:68-72. [ Show Abstract ]

Debris trapped behind contact lenses may be associated with adverse reactions in extended wear. Although streaks and clumps of cellular material have been reported after overnight wear of conventional materials, recent experience with several high-oxygen permeability (Dk), silicone-containing hydrogel lenses indicates that certain participants are prone to the development of a unique back surface debris. This debris forms as spherical, translucent entities and results in depressions within the ocular surface after lens removal. Little information is known about these spherical bodies, particularly with respect to their composition and development. In this report, we provide photographic evidence of this debris (sometimes termed 'mucin balls' or 'lipid plugs'), discuss its differential diagnosis and describe a case in which material seems to be embedded in the epithelium as a direct consequence of their presence.

Sorbara,L., Chong,T., Fonn,D. Visual acuity, lens flexure, and residual astigmatism of keratoconic eyes as a function of back optic zone radius of rigid lenses. Contact Lens and Anterior Eye 2000;23,2:48-52. [ Show Abstract ]

The purpose of this study was to determine whether the visual acuity of keratoconic eyes was affected by alteration of back optic zone radii (BOZRs) of rigid gas permeable lenses (RGP) contact lenses. Visual acuity, spherical and sphero-cylindrical over-refraction and keratometry of the front surface of the RGP lenses of nine keratoconic eyes were measured. The BOZR of the five lenses varied from steeper to flatter than that habitually worn by the subjects. The steepest lenses produced significantly greater lens flexure and residual astigmatism (P<0.002) and worse high and low contrast visual acuity with the spherical over-refraction (P<0.05). There was no statistical difference in visual acuity across the range of BOZR when a sphero-cylindrical over-refraction was applied. Thus reduced visual acuity in keratoconus with steep lenses is likely due to uncorrected residual astigmatism from a combination of several possible sources. © 2000 British Contact Lens Association.

1999

Dumbleton,K. A., Chalmers,R. L., Richter,D. B., Fonn,D. Changes in myopic refractive error with nine months' extended wear of hydrogel lenses with high and low oxygen permeability. Optometry and Vision Science 1999;76,12:845-849. [ Show Abstract ]

Background: A small but significant increase in myopia after extended wear of low oxygen permeability (Dk) hydrogel lenses has been previously reported; however, the specific impact of hypoxia on refractive status and corneal curvature with extended wear are not well documented. The purpose of this study was to compare the refractive changes induced over a period of 9 months' extended wear with high-Dk fluorosiloxane hydrogel lenses and low-Dk hydrogel lenses. Methods: Adapted daily wear contact lens wearers were randomly assigned to one of two groups. The low-Dk group wore etafilcon A (Dk = 28) for up to 7 days and 6 nights and the high-Dk group wore Iotrafilcon A (Dk = 140) for up to 30 days and nights. Refractive error and corneal curvature were measured at 3-month intervals over 9 months of extended wear. Results: The etafilcon A group demonstrated an average increase in myopia of 0.30 D over the 9-month period; however, no change in spherical myopic correction was measured in the Iotrafilcon A group. The cylindrical component did not change in either group. A stratified analysis revealed a greater increase in myopia for low myopes than moderate myopes in the etafilcon A group but no difference in the Iotrafilcon A group. Keratometric analysis revealed no change in the etafilcon A group and a small degree of central corneal flattening in both major meridians of 0.35 D in the Iotrafilcon A group. Conclusions: Nine months of extended wear of low-Dk lenses is associated with a small degree of myopic progression in adult myopes that appears to be reversible. Wearing fluorosiloxane-hydrogel lenses of high-Dk had no impact on refractive error and may be associated with a small degree of central corneal flattening.

Fonn,D., Du Toit,R., Simpson,T. L., Vega,J. A., Situ,P., Chalmers,R. L. Sympathetic swelling response of the control eye to soft lenses in the other eye. Investigative Ophthalmology and Visual Science 1999;40,13:3116-3121. [ Show Abstract ]

PURPOSE. To compare central corneal swelling and light scatter after 8 hours of sleep in eyes wearing high- and low-Dk hydrogel lenses and to the contralateral control eyes. METHODS. Twenty neophyte subjects wore a Lotrafilcon A (Dk, 140; Ciba Vision, Duluth GA) silicone hydrogel lens and an Etafilcon A (Dk, 18; Acuvue; Vistakon, Jacksonville, FL) 58% water content hydrogel lens of similar center thickness in random order in the right eye only, for overnight 8-hour periods. The contralateral nonwearing left eyes served as controls. Central corneal thickness was measured using an optical pachometer and light scatter using a Van den Berg stray-light meter before lens insertion, after lens removal on waking, and every 20 minutes for the next 3 hours. RESULTS. Central corneal swelling induced by the Etafilcon A lens on eye opening was significantly higher than with the Lotrafilcon A lens (8.66% ± 2.84% versus 2.71% ± 1.91%; P < 0.00001). Light scatter induced by the Etafilcon A lens on eye opening was significantly higher than with the Lotrafilcon A lens (46.09 ± 5.62 versus 42.78 ± 6.07 Van den Berg units, P = 0.0078). The swelling of the control eyes paired with the Etafilcon A lens- wearing eyes was also slightly but significantly higher than that of the control eyes paired with the Lotrafilcon A lens-wearing eyes (2.34% ± 1.26% versus 1.44% ± 0.91%; P = 0.0002). Light-scatter measurements were not significantly different between control sets of eyes but showed the same trend. CONCLUSIONS. In neophyte subjects, corneal swelling of the contralateral control eyes appears to be influenced by the swelling of the fellow lens-wearing eyes - that is, the swelling of the contralateral control eye was significantly lower when there was less swelling of the fellow eye wearing the high-Dk lens. Although there was no statistically significant difference in light-scatter measurements between the control sets of eyes, a trend similar to the corneal swelling results was observed, which could be used to support the suggestion that this may he a sympathetic physiological response rather than an unusual sampling coincidence.

Fonn,D., Situ,P., Simpson,T. Hydrogel lens dehydration and subjective comfort and dryness ratings in symptomatic and asymptomatic contact lens wearers. Optometry and Vision Science 1999;76,10:700-704. [ Show Abstract ]

Purpose. To determine whether lens dehydration correlates with discomfort, dryness, and noninvasive tear break-up time in symptomatic and asymptomatic contact lens wearers and whether dehydration of the two lens types varies. Method. Twenty hydrogel contact lens wearers with dryness- related symptoms and 20 asymptomatic wearers wore an Etafilcon A lens (Acuvue; Vistakon, Inc., Jacksonville, Florida) in one eye and an Omafilcon A lens (Proclear; Biocompatibles, Norfolk, Virginia) in the contralateral eye for 7 h in a randomized, double-masked study. Lens water content was measured before and after 7 h of lens wear and prelens noninvasive tear film break-up time (NIBUT) was measured immediately after insertion and after 5 h of lens wear. Subjective comfort and dryness were rated at 0, 1, 3, 5, and 7 h of lens wear. Results. The symptomatic group had significantly reduced prelens NIBUT, decreased comfort, and increased dryness, but there was no difference between lenses for these variables. The Omafilcon-A lenses dehydrated significantly less than the Etafilcon A lenses, but there was no significant difference in lens dehydration between two subject groups. Conclusion. No correlation was found between lens dehydration and subjective dryness and comfort. Symptomatic hydrogel contact lens wearers with decreased wearing time had measurably decreased comfort, increased dryness ratings, and reduced NIBUT.

Fonn,D., Situ,P., Simpson,T. L. Oxygen and contact lens wear. Chin J Optom and Ophthalmol 1999;1,3:185-189.

Vega,J. A., Simpson,T. L., Fonn,D. A noncontact pneumatic esthesiometer for measurement of ocular sensitivity: A preliminary report. Cornea 1999;18,6:675-681. [ Show Abstract ]

Purpose. The aim of this investigation was to evaluate a prototype noncontact pneumatic esthesiometer for measuring sensitivity of the eye. Methods. To evaluate the instrument's repeatability, central corneal sensitivity was recorded on two separate occasions with a 24-h interval between the two measures. In a separate experiment, corneal edema was induced with a thick hydrogel lens, and the eye was closed and patched. Corneal sensitivity was measured before wearing the lenses for 3 h, immediately after lens removal, and 15 min later. Corneal sensitivity also was measured before the instillation of a single drop of proparacaine (Alcaine, 0.5%) and at 2 and 18 min later. Sensitivity was measured at the corneal apex and at a temporal conjunctival location 3 mm from the limbus. Results. A high correlation was found between clays 1 and 2 (r = 0.90; p = 0.0001). The coefficient of repeatability (COR = 0.87 mm Hg) showed that 95% of the difference between test and retest measures were between ±0.87 mm Hg. Corneal sensitivity decreased by 55% after lens-induced corneal swelling and by 159% after instillation of the topical anesthetic. Central corneal sensitivity was found to be significantly higher than that of the temporal conjunctiva (p = 0.0001). Conclusion. We conclude that this pneumatic esthesiometer provides repeatable and reliable measures of ocular-surface sensitivity.

1998

Elliott,M., Fandrich,H., Simpson,T., Fonn,D. Analysis of the repeatability of tear break-up time measurement techniques on asymptomatic subjects before, during and after contact lens wear. Contact Lens and Anterior Eye 1998;21,4:98-103. [ Show Abstract ]

This study assessed the repeatability of various methods of measuring tear break-up time (TBUT) with and without soft contact lenses (CLs).TBUT was measured on 22 subjects with the tearscope, videokeratoscope and slit-lamp before and after 30 min of soft CL wear, and immediately after CL removal. Slit-lamp corneal TBUT was measured with fluorescein and without fluorescein while wearing CLs. TBUT was measured three times on the right eye only, using each technique in randomised order. TBUT measurements on CLs were repeated a second day. TBUT measurements were highly variable under all conditions and our results indicated a lack of correlation between techniques. The videokeratoscope was the least repeatable; while the tearscope was the most repeatable technique.

Elliott,M., Simpson,T., Richter,D., Fonn,D. Repeatability and comparability of automated keratometry: The Nikon NRK-8000, the Nidek KM-800 and the Bausch and Lomb keratometer. Ophthalmic and Physiological Optics 1998;18,3:285-293. [ Show Abstract ]

This study assessed the repeatability of the Nikon NRK-8000, the Nidek KM-800 and the Bausch and Lomb keratometer. In addition, the comparability of the Nikon NRK-8000 and the Nidek KM-800 are evaluated relative to the Bausch and Lomb keratometer. Measurements were taken with all three techniques on two separate occasions with a test-retest separation of at least 24 hr. The right eyes of 30 normal subjects were used. Repeatability and comparability statistics and plots were generated using matrix representations of dioptric power. The Nidek KM-800 coefficient of repeatability values were found to be 0.345, 0.187, and 0.321 in the vertical, torsional, and horizontal meridians while the Nikon NRK-8000 values were 0.346, 0.232, and 0.276 respectively.

Pritchard,N., Fonn,D. Post-lens tear debris during extended wear of hydrogels. Canadian Journal of Optometry 1998;60,2:87-91. [ Show Abstract ]

Debris entrapment after overnight wear of hydrogel lenses has been implicated as a cause of adverse ocular responses. We conducted two short-term pilot studies to determine if post-lens debris is related to the duration of lens wear, lens binding after overnight wear, movement of the lens prior to sleep or lens type. Debris and lens movement patterns upon waking were examined after one night (1N), one day and one night (1D+N) and one week of extended wear (6N). Three lens types were used on 10 subjects for the 1N experiment, and one lens type was used on 6 different subjects for the 1D+N and 6N experiment. Debris did appear to increase with duration of wear and was observed in approximately 60% of subjects after 1N. The appearance of debris observed ranged from light grey streaks to small clumped patches. Acuvue was bound more frequently than Medalist and NewVue. Movement was re-established after approximately 4 minutes of eye opening; however, the lenses appeared more adherent after 6N of overnight wear than after 1N or 1D+N. Debris dissipated after approximately 15 minutes (range 9 to 24 minutes) following eye opening. No statistical association was made between debris, lens binding, movement and lens type in this small group of subjects. These experiments demonstrated that debris appears to increase with duration of wear, may be associated with lens binding in a larger group and is quite difficult to view and quantify.

1997

Doughty,M. J., Fonn,D., Richter,D., Simpson,T., Caffery,B., Gordon,K. A patient questionnaire approach to estimating the prevalence of dry eye symptoms in patients presenting to optometric practices across Canada. Optometry and Vision Science 1997;74,8:624-631. [ Show Abstract ]

Objective. To collect questionnaire data from patients in a large clinical population that would allow for an estimate of the prevalence of self-reported symptoms of dry eyes. Methods. A 13-point questionnaire (The Canada Dry Eye Epidemiology Study, CANDEES) was mailed to all optometric practices in Canada in October 1994, with the request that it be completed by 30 successive nonselected patients. Results. Four hundred fifty sets of questionnaires (total, 13,517) were analyzed (a 15.7% return rate) from patients aged from 80 years; 55% were in the 21- to 50-year age group; 60.7% were female; and 24.3% were contact lens wearers. A total of 28.7% reported dry eye symptoms, of whom 24.2% reported concurrent dry mouth, 24.5% had worse symptoms in the morning, 30.3% reported concurrent lid problems, and 35.7% reported a history of allergies. Of the 3716 patients reporting symptoms, 62 (1.6%) were in the 'severe' category and 290 (7.8%) were in the 'constant but moderate' category. Contact lens wear, concurrent allergies, dry mouth, lid problems, or use of medications increased the chance of a patient reporting dry eye symptoms. Conclusions. The prevalence of patients reporting any level of symptoms of dry eyes was approximately 1 in 4; severe symptoms were reported by 1 in 225 patients.

Elliott,M., Simpson,T., Richter,D., Fonn,D. Repeatability and accuracy of automated refraction: A comparison of the Nikon NRK-8000, the Nidek AR-1000, and subjective refraction. Optometry and Vision Science 1997;74,6:434-438. [ Show Abstract ]

This study assessed the repeatability of the Nikon NRK-8000, the Nidek AR-1000, and subjective refraction. In addition, the accuracy of the Nikon and the Nidek were evaluated in comparison to subjective refraction. Measurements were taken with all 3 techniques on 2 separate occasions with a test-retest separation of at least 24 h. The right eyes of 30 normal subjects were used. Repeatability and accuracy statistics and plots were generated using matrix representations of dioptric power. Subjective refraction was the most repeatable method, with the coefficient of repeatability (COR) found to be 0.611, 0.224, and 0.490 in the vertical, torsional, and horizontal meridians. The autorefractors' COR was found to range from 0.712 to 0.826 for the vertical and horizontal meridians, whereas the torsional meridian ranged from 0.224 to 0.319.

1996

Fonn,D., Pritchard,N., Garnett,B., Davids,L. Palpebral aperture sizes of rigid and soft contact lens wearers compared with nonwearers. Optometry and Vision Science 1996;73,3:211-214. [ Show Abstract ]

Previous studies have shown that contact lens wear may affect palpebral aperture size (PAS). In this study, 74 wearers of rigid lenses were matched for sex and age with soft lens wearers and nonwearers. Partial face photographs were taken of all subjects, in the case of contact lens wearers, after lens removal. PAS was determined by measuring the resulting 35-mm transparencies on a Mitutoya profile projector. The mean PAS of the rigid lens wearers (9.76 ± 0.99 mm) was found to be significantly smaller than that of the soft lens wearers (10.24 ± 0.94 mm) and the nonwearers (10.10 ± 1.11 mm) (p = 0.0154, analysis of variance). There was no significant difference between the PAS of soft lens wearers and nonwearers. This study supports the hypothesis that rigid lens wear causes a decrease in PAS.

Pritchard,N., Fonn,D., Weed,K. Ocular and subjective responses to frequent replacement of daily wear soft contact lenses. CLAO Journal 1996;22,1:53-59. [ Show Abstract ]

Purpose: A significant number of soft contact lens wearers develop complications as a result of lens contamination. We conducted a single-blind 2 year clinical trial to determine if scheduled frequent replacement of lenses decreases complications. Methods: One hundred nineteen non-contact lens wearers were fit with soft contact lenses and randomly assigned to 1 or 3 month replacement schedules or a non-replacement (control) group. All subjects were fit with 0.04 mm thick HEMA (water content: 38%) lenses to be worn on a daily wear basis only. A single multipurpose solution was prescribed for cleaning and disinfection. Results: The 2-year results showed a significantly greater number of subjects in the non-replacement group exhibited microcysts, infiltrates, clinically significant corneal staining, and limbal and bulbar injection. As a result of lens deposition and damage, approximately twice the number of unscheduled lens replacements per subject were necessary in the non-replacement group compared with the 1 and 3 month replacement groups. Overall subject satisfaction with lens wear decreased in the non-replacement group and increased in the 1 and 3 month replacement groups over the 2-year period. Conclusions: Frequent replacement of soft lenses for daily wear as compared to non-replacement daily wear: 1) is less likely to cause contact lens induced complications; 2) reduces the number of unscheduled lens replacements; and 3) improves satisfaction with lens wear.

Sorbara,L., Fonn,D., Holden,B. A., Wong,R. Centrally fitted versus upper lid-attached rigid gas permeable lenses. Part I. Design parameters affecting vertical decentration. International Contact Lens Clinic 1996;23,3:99-104. [ Show Abstract ]

The purpose of this study was to develop rigid gas permeable lens designs that would facilitate upper lid attachment and central (interpalpebral) positions. A pilot study was conducted with trial lenses of varying back surface designs and axial edge lifts (AELs) with and without lenticulated front surface designs. From this study, the final upper lid attachment lens was designed to have high AELs (150–300 mm) and a minus carrier lenticulation. The centered lenses had an AEL of 110 mm, with thin edges. Forty-one neophyte subjects were fitted with these two designs to be worn contralaterally for an 8-month period during which the consistency of the lens position was examined. We were unable to achieve upper lid attachment on 6 subjects, and a further 10 were discontinued for other reasons. Of the remaining 25 subjects who completed the study, 80% had consistent upper lid attachment in the one eye and a centered lens in the other, over the eight visits. The balance of the subjects demonstrated correct lens positioning for at least 50% of the visits. The lens design factors that correlated with vertical decentration of the lenses were AEL (r = 0.614), edge thickness (r = 0.751), and front surface carrier radius (r = 0.654).

1995

Doughty,M. J., Potvin,R., Pritchard,N., Fonn,D. Evaluation of the range of areas of the fluorescein staining patterns of the tarsal conjunctiva in man. Documenta Ophthalmologica 1995;89,4:355-371. [ Show Abstract ]

Fluorescein dye is commonly used to highlight the tarsal conjunctiva in man to facilitate diagnosis of papillary conjunctivitis. A quantitative analysis of the fluorescein-highlighted features could be useful in both assignment of severity grades as well as for objective comparisons but no data is available on the distributions of sizes (areas) of these features. An exploratory, range-finding study was undertaken to provide data on feature areas that might be encountered. After application of fluorescein, 35 mm photographs were taken at a fixed distance with zone 1/zone 2 (Allansmith) of the tarsal plate aligned perpendicular to the camera. The photographs were projected, an overlay of 150 to 180 contiguous features outlined by fluorescein made and planimetry used to assess the areas and area distributions of the features on tarsal plates clinically graded with stages 1 to 4 papillary hypertrophy. For zone 1 of the tarsal plate in asymptomatic subjects, a fluorescein solution highlights the limits of features that enclose an area averaging 30,000 μm2 (range 8000 to 120,000; median area of close to 35,000 μm2). The areas of these features were generally normally distributed and there was little variation in feature areas across the zone. At different stages of clinical papillary conjunctivitis, the areas of the negative staining patterns are larger. Averages of 60,000 to 90,000 μm2, median values of close to 70,000 μm2 and individual feature areas up to 350,000 μm2 were seen in mildly symptomatic patients. These distributions were generally heterogeneous and showed a skewed distribution. Areas averaging up to 0.755 mm2 (range 0.6 to 3.2 mm2) were measured in moderate to severe papillary hypertrophy.

Fonn,D., Gauthier,C. A., Pritchard,N. Patient preferences and comparative ocular responses to rigid and soft contact lenses. Optometry and Vision Science 1995;72,12:857-863. [ Show Abstract ]

Patient preferences and ocular responses were compared between rigid and soft contact lenses by randomly fitting 32 neophyte subjects with a rigid lens in 1 eye and a soft lens in the contralateral eye. Twenty-seven of 32 subjects completed the 3-month study and 16 subjects were willing to continue for an additional 3-month extension. Subjects preferred the comfort and handling of the soft lens but preferred the vision provided by the rigid lens and initially its ease of maintenance. There was also a marked preference for the soft lens when all aspects of lens wear were compared. Objectively, the rigid lenses were responsible for more ocular changes than the soft lenses. Palpebral aperture sizes of the rigid gas permeable (RGP) wearing eyes decreased significantly (0.5 mm; p < 0.05) compared to the soft lens wearing eyes. The incidence of corneal staining was significantly greater in the rigid lens wearing eye (50% RGP vs. 22% soft) but limbal injection was greater in the soft lens wearing eye (18% soft vs. 6% RGP). Refractive sphere, cylinder, and corneal astigmatism decreased in the rigid lens wearing eye after 3 months. This daily wear clinical trial has shown a marked subjective preference for wearing soft lenses with fewer short-term ocular effects.

Potvin,R. J., Fonn,D., Sorbara,L. Comparison of polycarbonate and steel test surfaces for videokeratography. Journal of Refractive Surgery 1995;11,2:89-91. [ Show Abstract ]

BACKGROUND: Assessing video imaging systems for measuring corneal topography often requires test surfaces. Steel bearings have been employed, but manufacturers caution that high reflectance (>90%) relative to the eye (<10%) may compromise test findings. The differences between steel and polycarbonate test surfaces are quantified in this study. METHODS: Images of a steel and a polycarbonate sphere of known radius of curvature were obtained with the Tomey/Computed Anatomy Topographic Modeling System (TMS, Cambridge, Mass). Analysis was performed on the raw video data files and the resultant surface curvature estimates. RESULTS: The raw video images differed sufficiently to affect image processing. Polycarbonate yielded consistently better images. Many steel images (approximately 25%) contained data points that could not be processed; calculated surface contour was more variable for these. Differences were less obvious when these images were removed from the pool. CONCLUSIONS: Results support the manufacturer's caution against the use of steel surfaces for testing or calibration of the TMS instrument. Problems appear due to the fundamental differences in the intensity distributions of video images captured from high- and low-reflectance surfaces.

Pritchard,N., Fonn,D. Dehydration, lens movement and dryness ratings of hydrogel contact lenses. Ophthalmic and Physiological Optics 1995;15,4:281-286. [ Show Abstract ]

Previous studies have shown that soft lenses dehydrate during lens wear. The purpose of this study was to determine the dehydration time course of 38% water content non-ionic Medalist(®), 58% ionic Acuvue(®) and 74% non-ionic Permaflex(®) lenses, and the relationship between dehydration and in vivo diameter, movement and symptoms of dryness. Nineteen subjects randomly wore three pairs of lenses, each for 7 h. Lens movement and diameter were measured in vivo and hydration after lens removal at 1, 3 and 7 h. Dryness was rated by the subjects using a visual analogue scale. A separate experiment was conducted to measure hydration changes after 7 continuous hours of lens wear. The water content of all three lens types decreased significantly over 7 h with Acuvue decreasing more than the Permaflex and Medalist(®) lenses in the interrupted and continuous experiments (ANOVA P < 0.05). Dehydration of Acuvue was significantly greater in the 7 h continuous experiment (9.0 ± 2.6% H2O, ANOVA P = 0.0062) compared to the interrupted experiment. Hydration levels measured for Acuvue lenses on subjects for control purposes at 0, 1, 3 and 7 h showed no difference over time (ANOVA P = 0.0711). Movement of Permaflex lenses decreased 0.60 ± 0.57 mm (ANOVA P = 0.0005) over 7 h and the in vivo diameter of Acuvue lenses decreased by 0.12 ± 0.16 mm (ANOVA P = 0.0569). Dryness ratings increased significantly and equally for all three lenses over 7 h (ANOVA P = 0.9833). No correlation was found between lens dehydration, movement, diameter and dryness with the exception of a weak significant (r = 0.5, P < 0.05) correlation between dehydration and dryness for Permaflex. The results of the study suggest that dehydration of soft lenses over a 7 h period does not significantly affect the clinical performance (dryness and movement) of the three lens types.

Sivak,J. G., Herbert,K. L., Fonn,D. In vitro ocular irritancy measure of four contact lens solutions: Damage and recovery. CLAO Journal 1995;21,3:169-174. [ Show Abstract ]

We measured the potential toxicity of four contact lens solutions using an in vitro approach in which the optical quality of the cultured bovine lens was measured as a function of exposure to each substance tested. This approach uses an automated scanning laser to measure the focal variability of lenses contained in special culture cells and maintained under long-term culture conditions. The products tested included three rigid gas permeable contact lens conditioning solutions (Boston Conditioning Solution(TM), Boston Advance Conditioning Solution(TM), and a new formulation of Boston Advance Conditioning Solution(TM) [Polymer Technology]) and one soft contact lens disinfecting system (OptimEyes(TM); Core Technologies). The results indicate a wide range of toxicologic potential that corresponds, on a relative basis, with published in vivo evaluation of the same substances. Moreover, the results demonstrate that this in vitro system can be used to evaluate the potential for recovery from damage caused by the four solutions tested.

Skaff,A., Cullen,A. P., Doughty,M. J., Fonn,D. Corneal swelling and recovery following wear of thick hydrogel contact lenses in insulin-dependent diabetics. Ophthalmic and Physiological Optics 1995;15,4:287-297. [ Show Abstract ]

Thick, 0.34 mm, 38% water hydrogel lenses were fitted, under a pressure patch, to one eye of 18 type I diabetic patients (aged 18-40 years) to assess the acute response to hypoxia and hypercapnia; the response was compared with that in 18 healthy, aged-matched nondiabetic subjects; the closed-eye lens wear was started mid-morning. Pre-lens wear assessments were made of acuity, intraocular pressure (IOP), central corneal thickness (CCT) and corneal appearance by biomicroscopy. The mean duration of the diabetes was 13±7 years and the Baseline CCT values were marginally greater in diabetic patients (600±33μm) compared with a group of non-diabetic control subjects (584±26μm; P>0.5). A 7.7±2.1% increase in CCT was measured after 3h lens wear in the diabetic patients while an average 10.6±2.4% increase in CCT was measured in the control subjects (P<0.05). The recovery of corneal thickness to baseline values in diabetic patients was slower (at 44.8±2.0% per hour) than the control subjects (53.9±2.1 per hour; P<0.05) although recovery of corneal thickness occurred in both groups within 2.5-3h, IOP values (non-contact tonometry) were higher in the diabetic patients than in the controls (14.5±2.9 vs 12.4±1.7mmHg; P<0.01). Overall, those corneas with greater baseline CCT values tended to swell less than those with lower baseline CCT values (r = 0.582). Positive correlations were also found between corneal thickness and IOP and blood glucose. The diabetic patients thus tended to have slightly thicker corneas (but this could be related to blood glucose or IOP rather than true corneal disease) and also had corneas that tended to swell less with a contact lens stress test (but this could be constitutively due to the slight oedema already present). The different corneal response in diabetic patients may thus be the result of physical determinants such as initial oedema and IOP and not the result of a disease of the cornea itself.

1994

Potvin,R. J., Doughty,M. J., Fonn,D. Tarsal conjunctival morphometry of asymptomatic soft contact lens wearers and non-lens wearers. International Contact Lens Clinic 1994;21,11-12:225-231. [ Show Abstract ]

Soft contact lens wear is known to induce changes in the tarsal conjunctiva; qualitative grading is the current standard for recording such changes. This project was designed to investigate the usefulness of quantitatively assessing the morphometry of the tarsal conjunctiva, through a comparison of eight asymptomatic long-term soft contact lens wearers and eight nonwearers. The right tarsal plates were photographed after staining with fluorescein. A subjective assessment and grading of the fluorescein-highlighted tarsal plates was not able to distinguish the wearers and nonwearers. However, morphometry of the fluorescein-highlighted features across zone 1 of each tarsal plate revealed two basic patterns to the histograms of the areas of these features in both contact lens wearers and nonwearers. The analyses suggest that there are at least two types of "features" highlighted by fluorescein, evident in both wearers and nonwearers. Asymptomatic long-term soft lenswear appears to reduce the size of "small features" and increase the size and variability of "large features". These differences could be shown to be statistically significant. Further refinement of these quantitative assessment techniques should be useful in defining contact lens wear-related changes in the tarsal conjunctiva. © 1994.

1993

Doughty,M. J., Fonn,D. Pleomorphism and endothelial cell size in normal and polymegethous human corneal endothelium. International Contact Lens Clinic 1993;20,5-6:116-123. [ Show Abstract ]

The normal human corneal endothelium is composed of a tessellated mosaic of cells with different numbers of sides. A number of published studies indicate that while six-sided cells predominate (58-74%), significant numbers of five-sided (13-22%) and seven-sided (11-18%) are present along with occasional four-, eight-, nine- and even 10-sided cells. In polymegethous endothelia (associated with polymethyl methacrylate [PMMA] lenses and extended wear soft contact lenses [EW SCL]), the decline in the percentage of six-sided cells is associated with increases in the percentage of four-, five-, seven-, or eight-sided cells. Our analysis of photo slit-lamp micrographs revealed that the four- or five-sided cells tend to be smaller than the six-sided cells, whereas the seven-sided or larger cells are larger than six-sided cells. As a result, analyses of the average areas of each cell type indicate that the greater the pleomorphism (associated with polymegethism) the steeper the slope of a plot relating cell areas to the number of cell sides. The relationship is not necessarily linear (as suggested in previous reports), but does indicate that the remodeling of the endothelium (when significant cell loss is not evident) may follow some formal ordered process. © 1993.

Doughty,M. J., Fonn,D., Nguyen,K. T. Assessment of the reliability of calculations of the coefficient of variation for normal and polymegethous human corneal endothelium. Optometry and Vision Science 1993;70,9:759-770. [ Show Abstract ]

In endothelial morphometry, uncertainty exists concerning how many cells should be measured. A study was undertaken to calculate mean cell area and coefficient of variation (COV) of cell areas using different numbers of cells from photo-slitlamp pictures and published micrographs. Groups of 65, 95, or 165 tesselated cells were measured and area and COV values calculated in progressive sets of 5 cells; each pair of values was compared to that obtained using all cells in each group. The results show that, for both normal (homomegethous) and irregular (polymegethous) endothelia, even cell counts as low as 50 cells can usually provide average cell area values that are within 1 to 2% of the values estimated from larger groups of cells. A similar reliability was observed for estimates of COV for normal endothelia. However, for polymegethous endothelia, even with 100 cells analyzed, the estimates of COV generally only approached a +/- 4% reliability. This uncertainty in COV estimates should be considered in both comparative studies and in regression analyses of COV changes over time or other variables.

Elliott,D. B., Fonn,D., Flanagan,J., Doughty,M. Relative sensitivity of clinical tests to hydrophilic lens-induced corneal thickness changes. Optometry and Vision Science 1993;70,12:1044-1048. [ Show Abstract ]

The relative sensitivity of the van den Berg Straylightmeter, slitlamp biomicroscopy, a modified optical pachometer, Bailey-Lovie logMAR visual acuity (VA), and two glare tests (The Brightness Acuity Tester used with 10% contrast VA and Pelli-Robson contrast sensitivity) to hydrophilic contact lens-induced edema was assessed in 19 subjects (mean age 25.9 +/- 4.5 years). After baseline assessments, subjects wore thick hydrogel lenses on one eye which was patched tightly for 3 h. Assessments were repeated at frequent intervals after lens removal to assess recovery. None of the pachometer measurements returned to baseline within the 2-h monitoring period, although the majority were within 2% of baseline corneal thickness. The average time for the Straylightmeter scores to recover to baseline values after the lens removal was 90 min, which was similar to the time when visible edema at the slitlamp disappeared. The average time for return to baseline of logMAR VA and the two glare tests was consistently two to three times shorter than the time for the Straylightmeter score. The Straylightmeter therefore provided assessments of corneal edema similar to slitlamp examination and was more sensitive than VA or glare testing.

1992

Sorbara,L., Fonn,D., MacNeill,K. Effect of rigid gas permeable lens flexure on vision. Optometry and Vision Science 1992;69,12:953-958. [ Show Abstract ]

The flexure of spherical rigid lenses (various materials) and a soft lens was measured using automated over-keratometry on 6 adapted rigid lens wearers (12 eyes) whose corneal toricity ranged from 1.37 to 3.87 D. The results showed: (1) that there was no significant difference in flexure between polymethyl methacrylate (PMMA), silicone acrylate, and the fluorosilicone acrylate lenses (whose Dks ranged from 0 to 115). However, Advent (fluoropolymer) did flex significantly more than the other rigid lenses, and significantly less than the soft lens (Bausch & Lomb U4) and (2) that lens flexure of the rigid lenses did not alter over a 2-h period. We also measured high and low contrast visual acuity (HCVA and LCVA), and the results from subjects wearing Advent and the soft lens were significantly worse than with the other rigid lenses. Finally, the results of this study showed no correlation between rigid lens flexure and permeability and between rigid lens flexure and visual acuity when Advent was excluded from the linear regression analysis.

1991

Fonn,D., Gauthier,C. Prevalence of superficial fibrillary lines of the cornea in contact lens wearers and nonwearers. Cornea 1991;10,6:507-510. [ Show Abstract ]

Superficial corneal epithelial striations described as fibrillary lines have been documented as a common finding in normal and keratoconic eyes. We first noticed these fine white structures in both soft and rigid contact lens wearers. This prompted us to investigate whether the prevalence of these lines was greater in contact lens wearers than in non-lens wearers. Our results indicated that although the lines were more frequently observed in lens wearers (35.7% of 42 patients) than in the controls (19.0% of 42 patients), the difference was not statistically significant (p = 0.0867, χ2 analysis). We speculate that lens wear makes fibrillary lines more visible but is not responsible for their presence.

1990

Fonn,D., Anderson,R., Sorbara,L., Callender,MGE A survey of optometric contact lens use in Canada. Canadian Journal of Optometry 1990;52,3:90-95. [ Show Abstract ]

A questionnaire was mailed to all optometrists in Canada for the purpose of conducting a national survey on the habits of prescribing contact lenses and care products. Optometrists were requested to complete the survey for each practice for the time period of April 1, 1987 - April 1, 1988. The results of the survey revealed a response from slightly more than 10% (221) of the optometric practices. The vast majority of patients fitted with contact lenses (81%) were in the 17-44 year age group and 50% of the patients fitted with contact lenses in that period had never worn lenses previously or had not worn lenses for five years prior to the survey period. A high proportion of soft lenses (85%) were prescribed compared to rigid lenses (14%). Hydrogen peroxide was the preferred method of disinfection and extended wear was moderately popular.

1988

Fonn,D., Holden,B. A. Rigid gas-permeable vs. hydrogel contact lenses for extended wear. American Journal of Optometry and Physiological Optics 1988;65,7:536-544. [ Show Abstract ]

A clinical trail was conducted to compare the extended wear performance of rigid gas-permeable (RGP) contact lenses with that of soft lenses. Subjects were fitted with a RGP lens (Boston IV) in one eye and a soft lens (Bausch & Lomb 'O' series) in the other eye, and wore them on an extended wear basis for up to 3 months. No subjects developed any acute adverse reactions in the RGP lens-wearing eye. After the initial adaptation period, subject acceptance of RGP extended wear in terms of vision and comfort was superior. The RGP lenses also induced less chronic hypoxic stress than hydrogel lenses of comparable Dk/L, as evidenced by the presence of epithelial microcysts. Several complications of RGP extended wear were observed including lens binding, blepharoptosis, transient pupil size increases, and corneal staining. As hypoxia-induced corneal changes, such as microcysts and striae, were observed in the RGP lens-wearing eyes, we consider that these particular RGP lenses do not have adequate oxygen transmissibility for successful long-term extended wear. However, if RGP lens materials of higher oxygen transmissibility and better designs can be attained, the potential of RGP extended wear would appear promising.

Abstracts

2016

Moezzi A, Fonn D, Hutchings N, Simpson T. Mixed model analysis of corneal deswelling following overnight wear of silicone hydrogel lenses. Invest Ophthalmol Vis Sci 2016;57: E-abstract 1491. [ PDF ]

Yang M, Luensmann D, Fonn D, Woods J, Gordon K, Jones L, Jones D. Myopia prevalence in canadian school children. Optom Vis Sci 2016;93: E-abstract 165328. [ PDF ]

2015

Guthrie S, Woods J, Dumbleton K, Fonn D, Jones L. Contact lens discomfort management strategies of ECPs. Optom Vis Sci 2015;92: E-abstract 155050. [ PDF ]

2014

Payor R, Woods J, Fonn D, Situ P, Dillehay S, Griffin R, Tyson M, Jones L. Feasibility Testing of a Novel Soft Contact Lens Optical Design to Reduce Suspected Risk Factors for the Progression of Juvenile Onset Myopia. Invest Ophthalmol Vis Sci 2014;55: E-abstract 3638.

Luensmann D, Situ P, Fonn D, Jones L. Evaluation of the Performance of a New Silicone Hydrogel Color Contact Lens. Optom Vis Sci 2014;91: E-abstract 145179. [ PDF ]

2013

Dumbleton K, Richter D, Jones L, Fonn D. Eye examination frequency and contact lens purchase patterns. Optom Vis Sci 2013;90: E-Abstract 135126.

2012

Dumbleton K, Woods CA, Woods J, Moezzi A, Fonn D, Jones L. An Investigation Into The Role Of Masked Lens Replacement On Subjective Comfort And Vision With Aging Soft Contact Lenses . Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 4722.

Keir N, Richter D, Varikooty J, Jones L, Woods C, Fonn D. End Of Day Comfort Interpreted Using A Novel Cumulative Comfort Score. Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 4728.

Fonn D, Situ P, Paquette L, Keir N, Dillehay S. Extra-curricular Activities Of Myopic Children. Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 4722.

Dumbleton K, Woods C, Moezzi A, Fonn D, Jones L. The influence of masked lens replacement on subjective comfort and vision with aging soft contact lenses. Contact Lens & Anterior Eye 2012;35,S1:e38.

Keir N, Richter D, Varikooty J, Jones L, Woods C, Fonn D. End of day comfort interpreted using a novel cumulative comfort score for symptomatic contact lens wearers. Contact Lens & Anterior Eye 2012;35,S1:e37.

Keir N, Varikooty J, Richter D, Jones L, Woods C, Fonn D. Evaluation of lens surface appearance and ocular physiology with three silicone hydrogel daily disposables. Contact Lens & Anterior Eye 2012;35,S1:e6.

Varikooty J, Keir N, Richter D, Jones L, Woods C, Fonn D. Subjective comfort with three silicone hydrogel daily disposables in symptomatic contact lens wearers. Contact Lens & Anterior Eye 2012;35,S1:e7-e8.

Holden B, Fonn D, La Hood D, Moezzi A, Richter D, Lazon de la Jara P. Revised Estimate of the Oxygen Transmissibility Needed to produce Same Level of Overnight Corneal Swelling as that which occurs when No Lens is worn. American Academy of Optometry, 2012.

Fonn D, Holden B, Moezzi A, Lazon de la Jara P, La Hood D, Richter D. Overnight Corneal Swelling (ONCS) of the Contralateral Non-Lens Wearing Eye is affected by the amount of ONCS in the Lens Wearing Eye. American Academy of Optometry, 2012.

2011

Robinson B, Feng Y, Fonn D, Woods C, Gordon K, Gold D. Risk Factors For Visual Impairment- Report From A Population-based Study (C.U.R.E.S.) . Invest Ophthalmol Vis Sci 2011;52:ARVO E-Abstract 4217.

Keir N, Woods C, Fonn D. The Impact Of Lens Wear On In Vivo Wettability Of Silicone Hydrogel Contact Lenses . Invest Ophthalmol Vis Sci 2011;52:ARVO E-Abstract 6505.

Basuthkar S, Simpson T, Fonn D. Correlates of Subjective and Objective Measures of Ocular Discomfort . Invest Ophthalmol Vis Sci 2011;52:ARVO E-Abstract 1970.

Guthrie S, Woods J, Keir N, Dillehay S, Tyson M, Griffin R, Fonn D, Jones L, Irving E. Controlling lens induced myopia in chickens with peripheral lens design. Optom Vis Sci 2011;88:E-Abstract 110421.

Dumbleton K, Woods C, Fonn D, Jones L. An internet based survey to investigate lapsed contact lens wearers in Canada. International Society for Contact Lens Research (Napa Valley, California), 2011.

Woods J, Guthrie S, Keir N, Choh V, Fonn D, Jones L, Irving E. Myopia development – what can the chicken tell us?. Contact Lens & Anterior Eye 2011;34,Supplement 1:s13.

Luensmann D, Keir N, Richter D, Woods C, Fonn D. In vivo wettability changes over 3 days using daily disposable contact lenses. Optom Vis Sci 2011;88:E-abstract 115384.

Anderson T, Moezzi A, Varikooty J, Jones L, Woods C, Fonn D. A novel method for measuring contact lens movement and centration using a high speed camera and computer vision. Optom Vis Sci 2011;88:E-abstract 115439.

Dumbleton K, Woods C, Jones L, Fonn D. Comparing contact lens compliance and complications in a university clinic with private optometry offices. Optom Vis Sci 2011;88:E-abstract 110257.

Dumbleton K, Woods C, Jones L, Fonn D. A survey to investigate lapsed contact lens wearers in Canada. Optom Vis Sci 2011;88:E-abstract 110416.

Moezzi A, Situ P, Luensmann D, Fonn D, Woods C, McNally J, Jones L. Does comfort with aging silicone hydrogel lenses relate to changes in lens fit and conjunctival staining?. Optom Vis Sci 2011;88:E-abstract 115708.

Woods M, Dumbleton K, Woods C, Jones L, Fonn D. Do contact lens wearers remember what products they are using?. Optom Vis Sci 2011;87:E-abstract 115811.

Situ P, Simpson T, Jones L, Fonn D, Woods C. The relationship between solution induced corneal staining and ocular surface sensitivity. Invest Ophthalmol Vis Sci 2011;51:E-Abstract 6514.

2010

Fonn D, Moezzi A, Richter D, Woods CA. Can Overnight Lens Induced Corneal Swelling Be Minimised to Equal No Lens Wear Regardless of Oxygen Transmissibillity?. Optom Vis Sci 2010;87:E-Abstract 100318.

Fonn D, Woods C, Richter D, Moezzi A. Critical Oxygen Transmissiblity to Avoid Overnight Lens Induces Corneal Swelling. Contact Lens & Anterior Eye 2010;33,6:267.

Szczotka-Flynn LB, Albright M, Gillespie B, Kuo J, Fonn D, Lass JH. The Association Between Mucin Balls and a Decreased Incidence of Corneal Infiltrative Events During Extended Contact Lens Wear Canadian Uncorrected Refractive Error Study- A Pilot Study. Invest Ophthalmol Vis Sci 2010;51:ARVO E-Abstract 1517.

Robinson B, Feng Y, Woods C, Gold D, Gordon K, Fonn D. Canadian Uncorrected Refractive Error Study - A Pilot Study. Invest Ophthalmol Vis Sci 2010;51:ARVO E-Abstract 1718.

Dumbleton K, Richter D, Woods C, Jones L, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement in Canada. Ontario Association of Optometrists, 2010.

Keir N, Fonn D. Performance of visual acuity and contrast sentsitivity tests with multifocal contact lenses. Optom Vis Sci 2010;87:E-abstract 105912.

Dumbleton K, Richter D, Woods C, Jones L, Fonn D. Relationship between compliance with lens replacement and contact lens related problems in silicone hydrogel wearers. Optom Vis Sci 2010;87:E-abstract 100183.

Woods C, Dumbleton K, Richter D, Jones L, Fonn D. Compliance with lens care and contact lens case care and replacement. Optom Vis Sci 2010;87:E-abstract 100194.

Sorbara L, Richter D, Peterson R, Schneider S, Woods C, Jones L, Fonn D. Comparison between live and digital slit lamp images of corneal staining. Optom Vis Sci 2010;87:E-abstract 100083.

Peterson R, Fonn D, Woods C, Jones L. How to stop SICS!. Contact Lens & Anterior Eye 2010;33,6:272.

Dumbleton K, Woods C, Jones L, Richter D, Fonn D. The effect of compliance with replacement frequency on comfort and vision with silicone hydrogel lenses. Contact Lens & Anterior Eye 2010;33,6:263.

2009

Keir N, Srinivasan S, Jones L, Woods C, Fonn D. The performance of a silicone hydrogel daily disposable contact lens in a group of asymptomatic silicone hydrogel lens wearers. Asia Pacific Contact Lens Meeting (Hong Kong), 2009.

Fonn D, Moezzi A, Varikooty J. Average and individual overnight central corneal swelling with four different silicone hydrogel lenses. Contact Lens & Anterior Eye 2009;32,5:229.

Woods J, Woods CA, Fonn D. Using objective tests and novel subjective rating assessments to compare the performance of a new silicone hydrogel multifocal lens design to monovision. Contact Lens & Anterior Eye 2009;32,5:232.

Keir N, Varikooty J, Woods C, Fonn D. A novel in vivo method for measuring the refractive index of soft contact lenses using refractometry. Contact Lens & Anterior Eye 2009;32,5:229.

Dumbleton K, Woods C, Jones L, Guthrie S, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement. Contact Lens & Anterior Eye 2009;32,5:213.

Papas E, Decenz-Verbeten T, Fonn D, Kollbaum P, Situ P, Tan J, Woods CA. Predicting satisfaction with multifocal contact lenses. Contact Lens & Anterior Eye 2009;32,5:213.

Peterson R, Woods C, Jones L, Fonn D. The impact of rub and rinse on solution-induced corneal staining. ISCLR Meeting (Crete), 2009.

Dumbleton K, Woods C, Jones L, Fonn D. Does compliance with replacement frequency of silicone hydrogel lenses play a role in subjective comfort and vision rating?. ISCLR meeting (Crete, Greece), 2009.

Dumbleton K, Richter D, Guthrie S, Woods C, Jones L, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement. CAO (Charlottetown, PEI), 2009.

Fonn D, Moezzi A, Varikooty J. Distribution of overnight corneal swelling across subjects with 4 different silicone hydrogel lenses. Invest Ophthalmol Vis Sci 2009;50:E-abstract 5658.

Situ P, Simpson T, Jones L, Fonn D. Changes in corneal and conjunctival sensitivity with silicone hydrogel lens wear. Invest Ophthalmol Vis Sci 2009;50:E-abstract 6347.

Woods CA, Varikooty J, Keir N, Fonn D. Investigation of a novel in vivo method for measuring the refractive index of soft contact lenses using refractometry. Invest Ophthalmol Vis Sci 2009;50:E-abstract 5655.

Dumbleton K, Woods CA, Jones L, Fonn D. The role of compliance with replacement frequency of silicone hydrogel lenses on subjective comfort and vision. Optom Vis Sci 2009;86:E-abstract 090626.

Dumbleton K, Richter D, Woods CA, Jones L, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement in USA and Canada. Optom Vis Sci 2009;86:E-abstract 90615.

Moezzi A, Fonn D, Varikooty J, Richter D. Distribution of overnight central corneal swelling with high powered silicone hydrogel lenses. Optom Vis Sci 2009;86:E-abstract 90898.

Peterson R, Schneider S, Woods CA, Jones L, Fonn D. Optimising fluorescein observations of solution induced corneal staining. Optom Vis Sci 2009;86:E-abstract 95820.

Peterson R, Gorbet M, Woods CA, Fonn D. The transient nature of solution induced corneal staining. Optom Vis Sci 2009;86:E-abstract 90816.

Robinson B, Feng Y, Woods CA, Fonn D, Gold D, Gordon K. Canadian uncorrected refractive error study - preliminary findings from the pilot study. Optom Vis Sci 2009;86:E-abstract 95956.

Schneider S, Woods CA, Fonn D. Hyper-reflective cells observed by confocal microscopy with staining caused by different lens-solution combinations. Optom Vis Sci 2009;86:E-abstract 95912.

2008

Situ P, Simpson TL, Fonn D. Corneal and Conjunctival Mechanical and Chemical Sensitivity in Contact Lens Wearers. Invest Ophthalmol Vis Sci 2008;49: E-Abstract 4835.

Keir N, Boone A, Dumbleton K, Jones L, Woods C, Fonn D. In vivo and ex vivo wettability and the association with contact lens comfort. Contact Lens & Anterior Eye 2008;31,6:292.

Dumbleton K, Woods C, Schneider S, Fonn D. Comparison of signs and symptoms of dry eye when using ocular lubricants of differering viscosity. Optom Vis Sci 2008;85: E-abstract 80019.

Fonn D, Moezzi A, Varikooty J, Simpson TL. The effect of oxygen transmissibility on central and peripheral overnight corneal swelling with four different silicone hydrogel lenses. Optom Vis Sci 2008;85: E-abstract 85077.

Moezzi A, Fonn D, Varikooty J, Simpson TL. The effect of lens power on central and peripheral overnight corneal swelling with four different silicone hydrogel lenses. Optom Vis Sci 2008;85: E-abstract 85076.

Papas E, Decenzo-Verbeten T, Fonn D, Holden B, Kollbaum PS, Situ P, Woods CA. Utility of immediate evaluation of multifocal contact lens performance. Optom Vis Sci 2008;85: E-abstract 80113.

Peterson R, Woods CA, Fonn D. Comparing the CCLR grading system for corneal staining to a traditional 0-4 scale. Optom Vis Sci 2008;85: E-abstract 85324.

Schneider S, Simpson T, Woods C, Richter D, Fonn D. Hyper-reflective cells observed by confocal microscopy as an indicator of lens and lens care interactions. Optom Vis Sci 2008;85: E-abstract 80028.

Situ P, Simpson T, Fonn D. Ocular surface sensitivity and lens-solution induced corneal staining and symptoms. Optom Vis Sci 2008;85: E-abstract 85073.

Woods C, Dumbleton K, Fonn D, Schneider S. Signs and symptoms of dryness in habitual users of over-the-counter ocular lubricants. Optom Vis Sci 2008;85: E-Abstract 80014.

Woods C, Richter D, Fonn D. Rate of change of comfort in symptomatic and asymptomtic lens wearers. Optom Vis Sci 2008;85: E-Abstract 90014.

Woods J, Schneider S, Woods CA, Fonn D. Application of a novel method for evaluating corneal vascularization. Optom Vis Sci 2008;85: E-Abstract 80083.

Woods J, Woods CA, Fonn D. Comparison of the simplicity of completing an initial fit of symptomatic early presbyopes with monovision and an aspheric multifocal silicone hydrogel. Optom Vis Sci 2008;85: E-Abstract 80089.

Duench S, Simpson T, Tiso A, Grisan E, Ruggeri A, Fonn D. Measurement of average real-time red blood cell velocity in conjunctival vessels. Invest Ophthalmol Vis Sci 2008;49:E-Abstract 6051.

2007

Schneider S, Simpson T, Fonn D. Does fluorescein induce corneal epithelial hyper-reflectivity when using confocal microscopy. Optom Vis Sci 2007;84: E-Abstract 070075.

Duench S, Simpson T, Fonn D. Measurement of relative haemoglobin oxygen saturation in conjunctival vessels. Optom Vis Sci 2007;84: E-Abstract 075287.

Dumbleton K, Woods C, Jones L, Fonn D. Comfort and adaptation to silicone hydrogel lenses for daily wear. BCLA, 2007.

Dumbleton K, Woods J, Woods C, and Fonn D. Compliance with current contact lens care regiments. Optom Vis Sci 2007;84: E-abstract 070087.

Keir N, Simpson T, Jones L, Fonn D. The relationship between manifest refraction and higher order aberrations for wavefront-guided LASIK. Optom Vis Sci 2007;84: E-abstract 075084.

Woods J, Schneider S, Woods CA, Jones LW, Fonn D. Short term satisfaction and physiological response in wearers of high power hydrogel lenses refit with a custom silicone hydrogel lens. Optom Vis Sci 2007;84: E-abstract 070034.

Schneider S, Simpson T, Fonn D. Observations of inferior and central corneal subbasal nerve orientation obtained using confocal microscopy. Invest Ophthalmol Vis Sci 2007;48: E-abstract 3859.

Dumbleton K, Jones L, Woods CA, Feng Y, Moezzi A and Fonn D. Clinical performance of a hydrogen peroxide care regimen with silicone hydrogel lenses. Contact Lens & Anterior Eye 2007;30,5:301.

Sorbara L, Haque S, Fonn D, Simpson T. Refractive and topographic keratometric effects of Corneal Refractive Therapy for Hyperopia after one night of lens wear: comparison of two fitting parameters. Contact Lens & Anterior Eye 2007;30,5:286.

Varikooty J, Srinivasan S, Chan A, Subbaraman L, Woods C, Simpson T, Jones L, Fonn D. Clinical manifestations of upper lid staining in adapted silicone hydrogel lens wearers. British Contact Lens Association Annual meeting (Manchester, UK), 2007.

Situ P, Simpson T, Jones L, Fonn D. Conjunctival and corneal sensitivity associated with dry eye symptomatology. 6th Canadian Optometry Conference on Vision Science, Waterloo, Ontario, 2007.

Fonn D. Epithelial thickness changes with Hyperopic CRT RGP lenses. ISCLR meeting, Whistler, BC, Canada, 2007.

Keir N, Subbaraman L, Woods C, Jones L, Fonn D. Clinical impact of pre-soaking a silicone hydrogel lens in a MPS care solution on a group of symptomatic wearers. ISCLR meeting (Whistler, BC, Canada), 2007.

Fonn D. Assessment of ocular discomfort: oxygen and discomfort. ISCLR meeting, Whistler, BC, Canada, 2007.

Fonn D. Refractive error and corneal shape. ISCLR meeting, Whistler, BC, Canada, 2007.

2006

Moezzi A, Fonn D, Simpson T. Comparison of overnight corneal swelling induced by prototype lotrafilcon a toric versus balafilcon a toric. Optom Vis Sci 2006;83: E-Abstract 060095.

Lakshmi S, Cronje S, Jayanna K, Sweeney D, Fonn D. IACLE’s role in improving contact lens education in india: a case study. Optom Vis Sci 2006;83: E-Abstract 065114.

Woods C, Dumbleton K, German T, Dong G, Fonn D. The assessment of contact lens symptomology using wireless handheld communication devices. Optom Vis Sci 2006;83: E-Abstract 060073.

Keir N, Dumbleton K, Jones L, Fonn D. A 12 month clinical comparison of continuous wear surface modified and non-surface modified silicone hydrogel contact lens materials. Optom Vis Sci 2006;83: E-Abstract 060070.

Dumbleton K, Woods C, Jones L, Feng Y, Moezzi A, Fonn D. Comfort and adaptation to silicone hydrogel lenses for daily wear. Optom Vis Sci 2006;83: E-Abstract 060066.

Dumbleton K, Jones L, Woods C, Feng Y, Moezzi A, Fonn D. Clinical performance of a hydrogen peroxide care regimen with silicone hydrogel lenses. Optom Vis Sci 2006;83: E-Abstract 060069.

Keir N, Feng Y, Dumbleton K, Woods C, Jones L, Simpson T, Fonn D, Cohen S, Potter W. The influence of a lubricant eye drop on ocular discomfort in symptomatic hydrogel contact lens wearers. Optom Vis Sci 2006;83: E-Abstract 065249.

Varikooty J, Srinivasan S, Subbaraman L, Feng Y, Jones L, Simpson T, Fonn D. The influence of pre-soaking single-use etafilcon contact lenses on ocular comfort in symptomatic and asymptomatic contact lens wearers. Optom Vis Sci 2006;83:E-Abstract 065245.

Srinivasan S, Varikooty J, Subbaraman L, Chan A, Woods C, Simpson T, Jones L, Fonn D. Atypical manifestation of upper lid margin staining in silicone hydrogel lens wearers with symptoms of dry eye. Optom Vis Sci 2006;83:E-Abstract 065255.

Keir N, Situ P, Richter D, Jones L, Fonn D. Clinical performance of alexidine-based and polyquad-based multipurpose solutions when used with daily wear etafilcon lenses. Optom Vis Sci 2006;83: E-Abstract 065232.

Woods J, Woods C, Varikooty J, Jones L, Simpson T, Fonn D. A novel method of recording corneal staining that facilitates parametric analysis. Optom Vis Sci 2006;83: E-Abstract 065236.

Keir NJ, Simpson T, Jones L, Fonn D. Higher order aberration profiles differ for myopes and hyperopes before and 6 months after a CustomCornea LASIK procedure. Invest Ophthalmol Vis Sci 2006;47:E-Abstract 60.

Duench S, Simpson T, Jones L, Fonn D. Corneal staining is not correlated with limbal or bulbar redness in subjects using daily wear silicone hydrogel contact lenses. Invest Ophthalmol Vis Sci 2006;47: E-Abstract 87.

Feng Y, Dumbleton K, Keir N, Woods CA, Jones L, Simpson T, Fonn D. The influence of a guar-based lubricant eye drop on ocular discomfort in symptomatic hydrogel contact lens wearers. Invest Ophthalmol Vis Sci 2006;47:ARVO E-Abstract 2381.

Situ P, Simpson T, Jones L, Fonn D. Conjunctival and corneal sensitivity is associated with dry eye symptomatology. Invest Ophthalmol Vis Sci 2006;47: E-Abstract 262.

Lu F, Simpson T, Sorbara L, Fonn D. Moldability of the ocular surface in response to local mechanical stress. Invest Ophthalmol Vis Sci 2006;47,5:2390.

Harvey KM, Simpson T, Jones L, Fonn D. The effects of silicone hydrogel contact lens wear on the corneal epithelium’s sub-basal nerve fibre layer. Invest Ophthalmol Vis Sci 2006;47: E-Abstract 2393.

Schneider S, Fonn D, Simpson T. Central corneal clouding induced by PMMA lens wear during eye closure. Invest Ophthalmol Vis Sci 2006;47,5:2397.

Guthrie S, Simpson T, Varikooty J, Fonn D. Background subtraction and contrast enhancement for interferometric images of the human corneal tear film. Invest Ophthalmol Vis Sci 2006;47:E-abstract 2399.

Dumbleton K, Keir N, Varikooty J, Fonn D, Janakiraman P. Toric silicone hydrogel lenses for extended wear. Contact Lens & Anterior Eye 2006;29,4:184.

Rogers R, Jones L, Srinivasan S, Varikooty J, Fonn D. The influence of care regimen composition and wear time on ex vivo wettability of etafilcon contact lenses. Contact Lens & Anterior Eye 2006;29,4:189.

Dumbleton K, Moezzi A, Fonn D, Simpson T. Comparision of overnight corneal swelling induced by lotrafilcon b toric versus alphafilcon a toric lenses. Contact Lens & Anterior Eye 2006;29,4:193.

Keir N, Rogers R, Dumbleton K, Jones L, Fonn D. Comparision of ex-vivo wettability measurements of continuous wear surface treated and non-surface treated silicone hydrogel contact lens materials. Contact Lens & Anterior Eye 2006;29,4:195.

Keir N, Moezzi A, Fonn D, Varikooty J, Simpson T. Overnight corneal swelling of silicone hydrogel contact lenses with high oxygen transmissibility. Contact Lens & Anterior Eye 2006;29,4:196.

Srinivasan S, Chan C, Jones L, Simpson T, Fonn D. Diurnal variation in interior tear meniscus height that occurs in dry-eyed and non-dry-eyed participants. British Contact Lens Association Annual Meeting, Birmingham, England, 2006.

Woods C, Scott M, Woods J, Simpson T, Fonn D. Clinical grading scales: how many images is ideal?. Contact Lens & Anterior Eye 2006;29,4:207.

Varikooty J, Srinivasan S, Subbaraman L, Chan A, Woods C, Jones L, Simpson T, Fonn D. Clinical manifestations of upper lid staining in adapted silicone hydrogel lens wearers. Optom Vis Sci 2006;83:E-abstract 065256.

Jones L, Keir N, Situ P, Fonn D. The impact of post–insertion time on corneal staining and comfort with Group II hydrogel materials. 13th Symposium on the Materials Science and Chemistry of Contact Lenses (New Orleans, USA), 2006.

Woods C, Tsang K, Fonn D. Comparing gravimetric and refractive methods of measuring water content for various soft lenses. Optom Vis Sci 2006;83: E-abstract 065276.

Woods CA, Roy A, Fonn D. Radial power profiles of single vision slicone hydrogel lenses. Optom Vis Sci 2006;83: E-abstract 065286.

Keir N, Rogers R, Dumbleton K, Jones L, Fonn D. Comparison of ex vivo wettability measurements of continuous wear surface treated and non-surface treated silicone hydrogel contact lens materials. British Contact Lens Association Annual Meeting (Birmingham, England), 2006.

Duench S, Sorbara L, Simpson TL, Jones L, Fonn D. The use of fluorophotometry to measure corneal epithelial permeability to contact lenses and contact lens care regimens. Optom Vis Sci 2006;83:E-Abstract 65238.

2005

Dumbleton K, Keir N, Varikooty J, Fonn D. Corneal thickness changes over six months of contralateral extended wear with low and high DK hydrogel lenses. Optom Vis Sci 2005;82: E-Abstract 055109.

Feng Y, Simpson TL, Fonn D, Hickson–Curran S. The Effect of Soft Toric Contact Lens Wear on Corneal and Conjunctival Sensitivity Measured With a Belmonte Esthesiometer. Invest Ophthalmol Vis Sci 2005;46: E-Abstract 2071.

Schneider S, Simpson T, Fonn D. Repeatability of Normalized Light Scatter of the Cornea Determined Using Optical Coherence Tomography (OCT). Invest Ophthalmol Vis Sci 2005;46: E-Abstract 2751.

Lu F, Simpson TL, Sorbara L, Fonn D. The Relationship Between the Treatment Zone Diameter With Visual and Optical Performance in Hyperopic Corneal Refractive Therapy Lens Wearers. Invest Ophthalmol Vis Sci 2005;46: E-Abstract 2057.

Duench S, Simpson T, Jones L, Flanagan J, Fonn D. Assessment of the diurnal relationship between bulbar conjunctival redness, temperature and blood flow. Optom Vis Sci 2005;82: E-Abstract 055003.

Situ P, Simpson T, Jones L, Fonn D, Vehige J, Simmons P. The association between corneal & conjunctival sensitivity, tear film stability & ocular surface appearance in subjects with & without dry eye symptoms. Optom Vis Sci 2005;82: E-Abstract 050066.

Haque S, Fonn D, Simpson T, Jones L. Corneal, stromal and epithelial thickness changes following overnight CRT, comparing two high-Dk lens materials. Optom Vis Sci 2005;82: E-abstract 050041.

Keir N, Situ P, Richter D, Jones L, Sijpson T, Fonn D. Impact of post-insertion time on corneal staining, sensitivity and comfort with an FDA group II lens disinfected with various care regimens. Optom Vis Sci 2005;82: E-abstract 055103.

Lu F, Simpson T, Fonn D, Sorbara L. Corneal shape and optical performance after one night of lens wear with two different oxygen transmissible corneal refractive therapy lense. Optom Vis Sci 2005;82: E-abstract 050042.

Moezzi A, Fonn D, Varikooty J, Simpson T. Overnight corneal swelling of silicone hydrogel contact lenses with high oxygen transmissibility. Optom Vis Sci 2005;82: E-abstract 050083.

Srinivasan S, Chan C, Jones L, Simpson T, Fonn D. Diurnal variation in inferior tear meniscus height that occurs in dry eyed and non-dry eyed participants. Optom Vis Sci 2005;82: E-abstract 050064.

Varikooty J, Situ P, Jones L, Fonn D. Clinical performance of alexidine-based and polyquad-based multipurpose solutions when used with daily wear balafilcon lenses. Optom Vis Sci 2005;82: E-abstract 055100.

Vehige J, Simmons P, Feng Y, Situ P, Simpson T, Jones L, Fonn D. Does the subjective evaluation of symptoms of dryness (SESoD) as a single variable predict the severity of signs and symtpoms of dry eye disease?. Optom Vis Sci 2005;82: E-abstract 050067.

Keir N, Simpson T, Jones L, Fonn D. Factor analysis of postoperative outcome variables for a CustomCornea(R) LASIK clinical trial. Invest Ophthalmol Vis Sci 2005;46: E-abstract 4352.

Jones L, Keir N, Situ P, Fonn D. The impact of post-insertion time on corneal staining and comfort with Group II hydrogel mateials disinfected with various lens care regimens. Invest Ophthalmol Vis Sci 2005;46: E-abstract 917.

Lu F, Simpson T, Sorbara L, Fonn D. The relationship between treatment zone diameter with visual and optical performance in hyperopic corneal refractive therapy lens wearers. Invest Ophthalmol Vis Sci 2005;46: E-abstract 2057.

Situ P, Simpson TL, Jones L, Fonn D. Effect of symptoms of dryness, age, and gender on corneal and conjunctival sensitivity to cooling stimuli. Optom Vis Sci 2005;46: E-abstract 4448.

Sorbara L, Lu F, Fonn D, Simpson T. Topographic keratometric effects of corneal efractive therapy for hyperopia after one night of lens wear. Invest Ophthalmol Vis Sci 2005;46: E-abstract 2061.

Vaccari S, Simpson T, Jones L, Flanagan J, Fonn D. The assessment of diurnal variation of bulbar conjunctival hyperemia, temperature and conjunctival blood flow before and after sleep. Invest Ophthalmol Vis Sci 2005;46; E-abstract 2681.

Jones L, Keir N, Situ P, Fonn D. The impact of post-insertion time on corneal staining and comfort with group II hydrogel materials disinfected with various lens care regimens. British Contact Lens Association Annual Meeting, Brighton, England, 2005.

Keir N, Simpson T, Jones L, Fonn D. Factor analysis of postoperative outcome variables for a CustmCornea LASIK clinical trial. Graduate Student Research Conference( University of Waterloo, Ontario), 2005.

Sorbara L, Lu F, Fonn D, Simpson T. Topographic Keratometric Effects of Corneal Refractive Therapy for Hyperopia After One Night of Lens Wear. GOS, 2005.

2004

Situ P, Moezzi A, Fonn D, Simpson TL. Comparing perilimbal hyperemia after overnight wear of O2 Optix and Acuvue 2 contact lenses. Optom Vis Sci 2004;81,12s:59.

Fonn D, Moezzi A, Simpson TL, Situ P. Confirmation of a yoked corneal swelling response between the test and contralateral control eye. Optom Vis Sci 2004;81,12s:30.

Haque S, Fonn D, Sorbara L, Simpson TL. Corneal and epithelial thickness changes following one night of CRT gas permeable lens wear for hyperopia, measured with optical coherence tomography. Optom Vis Sci 2004;81,12s:27.

Lazon de la Jara P, Capaldi P, Williams L, Fonn D, Cronje S, Sweeney D, Holden BA. IACLE influence broad and beneficial to contact lens education in Latin America. Optom Vis Sci 2004;81,12s:268.

Lu F, Simpson TL, Sorbara L, Fonn D. Optical performance after one night of hyperopic corneal refractive therapy lens wear. Optom Vis Sci 2004;81,12s:72.

Dumbleton K, Keir N, Moezzi A, Jones L, Fonn D. Redness, dryness and comfort following refitting long-term low Dk lens wearers with silicone hydrogel lenses. Optom Vis Sci 2004;81,12s:31.

Sorbara L, Lu F, Fonn D, Simpson TL. Refractive and keratometric effects of corneal refractive therapy for hyperopia after one night of lens wear. Optom Vis Sci 2004;81,12s:72.

Jones L, Bayer S, Senchyna M, Subbaraman L, Glasier M, Dumbleton K, Fonn D. Rewetting drops influence comfort and protein deposition on silicone hydrogel contact lenses. Optom Vis Sci 2004;81,12s:57.

Jones L, Rahman S, Leech R, Simpson T, Fonn D. Determination of inferior tear meniscus height and inferior tear meniscus volume using optical coherence tomography . Invest Ophthalmol Vis Sci 2004;45: E-Abstract 144.

Bayer S, Jones LW, Senchyna M, Subbaraman L, Glasier M, Dumbleton K, Fonn D. Effect of rewetting drops on comfort and protein deposition of silicone hydrogel (Focus Night&Day) contact lenses. Invest Ophthalmol Vis Sci 2004;45,4:s65.

Dumbleton K, Jones L, Bayer S, Fonn D. Clinical performance and corneal staining associated with silicone hydrogel materials used on a daily wear basis. Contact Lens & Anterior Eye 2004;27,2:97-98.

Dumbleton K, MacDougall N, Jones L, Moezzi A, Fonn D, McNally J. Changes in hyperemia subsequent to refitting long-term low Dk wearers with silicone hydrogel lenses on a daily wear basis. Contact Lens & Anterior Eye 2004;27,2:102.

Varikooty JP, Simpson TL, Jones LW, Fonn D. Subjective sensations reported during the interblink interval reflect different components of ocular surface sensitivity. Invest Ophthalmol Vis Sci 2004;45: E-abstract 99.

Lu FU, Simpson TL, Sorbara L, Fonn D, Jones LW. The relationship between treatment zone diameter and visual, optical and subjective performance in CRT(TM) wearers. Invest Ophthalmol Vis Sci 2004;45: E-Abstract 1576.

Sorbara L, Lu FU, Kort R, Fonn D, Simpson TL. Topographic keratometric effects of corneal refractive therapy after one month of lens wear. Invest Ophthalmol Vis Sci 2004;45,4:65.

Vaccari S, Simpson T, Jones L, Fonn D. Assessment of diurnal variation of bulbar conjunctival hyperemia using a novel objective method. Invest Ophthalmol Vis Sci 2004;45: E-Abstract 4828.

Jones L, Bayer S, Dumbleton K, Fonn D. Corneal staining associated with silicone hydrogel materials used on a daily wear basis with ReNu and AOSept care regimens. International American Academy Meeting (Hawaii), 2004.

Bayer S, Jones L, Senchyna M, Subbaraman L, Glasier M, Dumbleton K, Fonn D. Effect of rewetting drops on comfort and protein deposition of silicone hydrogel (Focus Night & Day) contact lenses. Invest Ophthalmol Vis Sci 2004;45ARVO E-Abstract 1575.

Jones L, Rahman S, Leech R, Simpson T, Fonn D. Determination of inferior tear meniscus height and volume using optical coherence tomography. Tear Film and Ocular Surface Society (Puerto Rico), 2004.

Fonn D, Jones L, Chan A. Corneal staining does not affect the comfort of soft contact lens wear. Tear Film and Ocular Surface Society (Puerto Rico), 2004.

2003

Bayer S, Simpson T, Sorbara L, Fonn D. Variation of objective ocular redness related to age and gender. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 3703.

Lazon P, Capaldi P, Fonn D, Cronje S, Sweeney D, Holden B. Setting an educational standard in contact lens education in Latin America development of the IACLE accreditation examination. Optom Vis Sci 2003;80,12s:64.

Cronje S, Williams L, Sweeney D, Fonn D, Sorbara L, Holden B, IACLE team. Providing educational support to contact lens educators. Optom Vis Sci 2003;80,12s:68.

Fonn D. Has silicone hydrogels had an effect on dryness and discomfort symptoms?. Contact Lens & Anterior Eye 2003;26,4:203.

Sorbara L, Lu F, Kort RA, Fonn D, Simpson TL. Refractive, keratometric and visual effects of corneal refractive therapy after one month of lens wear. Optom Vis Sci 2003;80,12s:189.

Varikooty J, Simpson TL, Fonn D. Changes in ocular surface temperature and redness. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 3752.

MacDougall N, Situ P, Chan A, Simpson T, Jones L, Fonn D, Hakim O. Low contrast acuity, contrast sensitivity and higher order aberration outcomes following Custom LASIK. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 2629.

Situ P, Simpson TL, Fonn D. Objective measure of halo size with multifocal contact lenses. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 2615.

Wang J, Simpson TL, Fonn D. Objective measurements of corneal light backscatter during corneal swelling using Optical Coherence Tomography. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 3666.

Sorbara L, MacDougall N, Situ P, Chan A, Hakim O, Fonn D, Jones L, Simpson T. Relationship between corneal shape and refractive power pre- and post-Custom LASIK. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 2615.

Simpson TL, Fonn D, Wang J, Hickson-Curran S. Suprathreshold scaling of limbal mechanical stimuli. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 3709.

Lu F, Sorbara L, Kort RA, Fonn D, Simpson T, Jones L. Topographic keratometric effects of corneal refractive therapy after one night of lens wear. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 3699.

Fonn D. Corneal and epithelial thickness changes from overnight wear of CRT lenses. Contact Lens & Anterior Eye 2003;26,4:204.

Jones L, Rahman S, Leech R, Simpson T, Fonn D, Vehige JG, Simons PA. Determination of tear meniscus height using a novel method based upon Optical Coherence Tomography. Invest Ophthalmol Vis Sci 2003;44: E-Abstract 2461.

Fonn D. New discoveries on how the cornea changes with contact lens wear. British Contact Lens Association Conference, Brighton, England, 2003.

Fonn D. Contact lenses for life, what can be done for presbyopes. International Soceity for Contact Lens Research, Biennial Scientific Conference, Mallorca, Spain, 2003.

Jones L, Rahman S, Leech R, Simpson T, Fonn D. The use of optical coherence tomography to determine tear volume. International Society for Contact Lens Research (Mallorca, Spain), 2003.

Lu F, Sorbara L, Kort RA, Fonn D, Simpson T, Jones L. Effects of corneal shape after one night of CRT lens wear. University of Waterloo Graduate Research Conference Handbook, 2003.

MacDougall N, Situ P, Chan A, Fonn D, Simpson TL, Jones L, Hakim O. Quality of vision outcomes following custom LASIK. University of Waterloo Graduate Research Conference Handbook, 2003.

Jones L, Leech R, Rahman S, Simpson T, Fonn D. A novel method to determine tear prism height. Contact Lens & Anterior Eye 2003;26,4:206-207.

Jones L, Dumbleton K, Fonn D, Dillehay S. Comfort and compliance with frequent replacement soft contact lenses in North America: a survey. Contact Lens & Anterior Eye 2003;26,4:205-206.

Haque S, Jones L, Fonn D, Simpson T, Sorbara L. Changes in topographical thickness of the total cornea following 4 weeks of overnight CRT RGP lens wear measured with OCT. Optom Vis Sci 2003;80,12s:243.

Jones L, Rahman S, Leech R, Simpson T, Fonn D, Vehige J, Simmons P. Determination of tear meniscus height using a novel method based upon optical coherence tomography. BCLA Conference (Brighton, England), 2003.

2002

Wang J, Fonn D, Simpson T, Jones L. The measurement of corneal epithelial thickness using the OCT in response to hypoxia induced by soft contact lens and eye closure. Contact Lens & Anterior Eye 2002;25,1:36.

Fonn D. Contact lens correction of presbyopia – how to make it work. The Irving Fatt Memorial Lecture, The Annual Sarver Series Continuing Education, University of California, Berkeley, California, 2002.

Sorbara L, Bayer S, Simpson T, Fonn D. Comparison of objective, clinical and self-reported bulbar conjunctival redness. Invest Ophthalmol Vis Sci 2002;43: E-Abstract 119.

Jones L, Dumbleton K, MacDougall N, Fonn D. Subjective comfort with daily wear of silicone hydrogel contact lenses. CIBA-Vision Educators Meeting abstract book (Atlanta, Georgia), 2002.

Dumbleton K, MacDougall N, Jones L, Simpson T, Fonn D. Patient satisfaction with continuous wear contact lenses versus LASIK. CIBA-Vision Educators Meeting abstract book (Atlanta, Georgia), 2002.

Jones L, Dumbleton K, Fonn D. A survey to determine the patient comfort and compliance with different contact lens replacement schedules. CIBA-Vision Educators Meeting abstract book (Atlanta, Georgia), 2002.

Jones L, Leech R, Rahman S, Simpson T, Fonn D. A novel method to determine tear prism height. Optom Vis Sci 2002;79,12s:252.

Jones L, Dumbleton K, Fonn D, Dillehay S. Comfort and compliance with frequent replacement soft contact lenses. Optom Vis Sci 2002;79,12s:259.

MacDougall N, Situ P, Chan A, Fonn D, Jones L, Simpson T. Comparison between orbscan and ultrasound central corneal thickness measurements. Optom Vis Sci 2002;79,12s:264.

Bayer S, Simpson T, Sorbara L, Fonn D. Hawthorne effect related to ocular redness with artificial tears. Optom Vis Sci 2002;79,12s:306.

Sorbara L, Kort R, Lu H, Simpson T, Fonn D. Overnight refractive and keratometry effects of refractive therapy. Optom Vis Sci 2002;79,12s:127.

Dumbleton K, Jones L, MacDougall N, Simpson T, Fonn D. Patient satisfaction with silicone hydrogel continuous wear contact lenses. Optom Vis Sci 2002;79,12s:8.

Sorbara L, Kort RA, Lu FH, Simpson T, Fonn D. Refractive and keratometric effects of corneal refractive therapy after one night of lens wear. Optom Vis Sci 2002;79,12s:.

MacDougall N, Situ P, Chan A, Fonn D, Jones L, Simpson T. Single site 6-month clinical outcomes for custom LASIK. Optom Vis Sci 2002;79,12s:173.

Wang J, Fonn D, Simpson T. Topographical thickness changes of the epithelium and total corneal after overnight lens wear of CRT™ rigid gas permeable lenses measured with OCT. Optom Vis Sci 2002;79,12s:2.

Varikooty J, Simpson T, Jones L, Fonn D. Ocular discomfort during tear film drying. Invest Ophthalmol Vis Sci 2002;43: E-abstract 3106.

Wang JH, Fonn D, Simpson TL, Jones L. Pre-corneal and pre- and post-lens tear film thickness measured with optical coherence tomography. Invest Ophthalmol Vis Sci 2002;43: E-abstract 3078.

Situ P, du Toit R, Fonn D, Simpson T. Refractive error in presbyopes after 6 months of monovision contact lens wear. Invest Ophthalmol Vis Sci 2002;43,4:125.

Jones L, MacDougall N, Sorbara L, Fonn D. The clinical performance of a polyquad-based care regimen with a silicone-hydrogel material used on a daily wear basis. Contact Lens & Anterior Eye 2002;25,4:211.

2001

Moezzi A, Fonn D, Sorbara L, Simpson T. Effects of contact lens induced swelling on anterior and posterior corneal surfaces. Optom Vis Sci 2001;78,12s:303.

Dumbleton K, Chalmers R, Bayer S, Fonn D, NcNally J. Lens base curve and subjective comfort with silicone hydrogel continuous wear lenses. Optom Vis Sci 2001;78,12s:227.

Sorbara L, Machalitza A, Simpson T, Jones L, Fonn D. Is tear turnover rate measured by fluorophotometry a valuable tool in identifying dry eye patients?. Invest Ophthalmol Vis Sci 2001;42,4:s39 #218.

Varikooty JP, Simpson TL, Jones L, Fonn D. Ocular discomfort during tear drying: A method to simultaneously acquire discomfort ratings, ocular surface video and sensation attributes on a pseudocontinuous scale. Invest Ophthalmol Vis Sci 2001;42,4:s941 #5038.

Simpson T, Feng Y, Fonn D, Hickson-Curran S. Scaling ocular discomfort induced using different concentrations of CO2. Optom Vis Sci 2001;78,12s:119.

MacDougall N, Sorbara L, Jones L, Fonn D. The clinical performance of a polyquad-based care regimen with a silicone-hydrogel material used on a daily wear basis. Optom Vis Sci 2001;78,12s:309.

Wang J, Fonn D, Simpson T. Topographical thickness of the epithelium and total cornea after hydogel and PMMA contact lens wear and eye closure. Optom Vis Sci 2001;78,12s:303.

Situ P, Simpson TL, Fonn D. Objective measure of ocular redness: the repeatability and the association with subjective scale. Invest Ophthalmol Vis Sci 2001;42,4:s597 #3212.

du Toit R, Situ P, Simpson T, Fonn D. Predicting preference for monovision and bifocal contact lens wear: results from a one year clinical trial. Invest Ophthalmol Vis Sci 2001;42: E-abstract 3170.

Wang J, Fonn D, Simpson T, Jones L. Tear film thickness measured with optical coherence tomography. International Society for Contact Lens Research, Sun Valley, Idaho, 2001.

Dumbleton K, Fonn D, Jones L, Williams-Lyn D, Richter D. Severity and management of contact lens related complications with continuous wear of high Dk silicone hydrogel lenses. BCLA Conference, Brighton, England, 2001.

Varikooty JP, Simpson TL, Jones L, Fonn D. Ocular discomfort during tear drying. International Society for Contact Lens Research, Sun Valley, Idaho, 2001.

2000

du Toit R, Situ P, Simpson T, Fonn D. Factors that discriminate between monovision and bifocal contact lens preference. Optom Vis Sci 2000;77,12s:160.

Sorbara L, Simpson T, Fonn D. Comparison of an objective method of measuring bulbar redness to the use of traditional grading scales. Optom Vis Sci 2000;77,12s:262.

du Toit R, Pritchard N, Simpson T, Heffernan S, Fonn D. Comparison of three different types of rating scales. Optom Vis Sci 2000;77,12s:261.

Fonn D, du Toit R, Situ P, Simpson T, Bayer S. Determination of lens prescription for monovision and Acuvue Bifocal contact lenses. Optom Vis Sci 2000;77,12s:160.

du Toit R, Situ P, Simpson T, Fonn D. Results of a one year clinical trial comparing monovision and bifocal contact lenses. Optom Vis Sci 2000;77,12s:18.

Dumbleton K, Fonn D, Jones L, Williams-Lyn D, Richter D. Severity and management of contact lens related complications with continuous wear of high Dk silicone hydrogel lenses. Optom Vis Sci 2000;77,12s:216.

Situ P, du Toit R, Simpson T, Fonn D. The detection of change in tests of tear film break-up time (BUT) and phenol red thread test. Optom Vis Sci 2000;77,12s:267.

Wang J, Fonn D, Simpson T, Jones L. The measurement of corneal epithelial thickness using the OCT in response to hypoxia induced by soft contact lens and eye closure. Optom Vis Sci 2000;77,12s:170.

Situ P, du Toit R, Simpson T, Fonn D. Visual function assessments and subjective vision ratings of bifocal and monovision contact lens wearers. Optom Vis Sci 2000;77,12s:161.

Simpson T, Lau J, Jones L, Fonn D. Chemical properties predict the dimensions of ocular discomfort of ophthalmic drops. Invest Ophthalmol Vis Sci 2000;41: E-abstract 1440.

Situ P, Simpson T, du Toit R, Fonn D. Comparison of Acuvue bifocal and habitual monovision lenses on binocular function and subjective vision rating in adapted monovision wearers. Invest Ophthalmol Vis Sci 2000;41,4:s72.

du Toit R, Situ P, Simpson T, Fonn D, Begley C. The ocular surface and symptoms of presbyopes before and after six months of contact lens wear. Invest Ophthalmol Vis Sci 2000;41,4:s73.

Fonn D, Wang J, Simpson T. Topographical thickness of the epithelium and total cornea using optical coherence tomography. Invest Ophthalmol Vis Sci 2000;41,4:s675.

Jones L, Dumbleton K, Simpson T, Fonn D. Direct vs off-line grading of bulbar and limbal hyperemia: a comparison of high Dk vs low Dk extended wear lenses. Contact Lens & Anterior Eye 2000;23,4:175.

Simpson T, Lau J, Jones L, Richter D, Dumbleton K, Fonn D. Physical chemistry predicts the dimensions of ocular discomfort of ophthalmic drops. Contact Lens & Anterior Eye 2000;23,4:172.

Simpson T, Lau J, Jones L, Fonn D. Chemical properties predict the dimensions of ocular discomfort of ophthalmic drops. BCLA Conference (Birmingham, UK), 2000.

1999

Dumbleton K, Jones L, Williams-Lyn D, Fonn D, Chalmers R. Mucin ball post lens debris in high Dk silicone hydrogel wearers. Optom Vis Sci 1999;76,12s:226.

Chan A, Taylor S, du Toit R, Chong T, Fonn D. Determination of the accuracy of the glare scatter test: comparison of GST data to bagolini lens-induced glare. Optom Vis Sci 1999;76,12s:229.

Jones L, Dumbleton K, Simpson T, Fonn D. Direct vs off-line grading of bulbar and limbal hyperemia: a comparison of high Dk vs low Dk extended wear lenses. Optom Vis Sci 1999;76,12s:14.

Dumbleton K, Jones L, Williams-Lyn D, Fonn D, Chalmers R. Mucin ball post-lens debris in high-Dk silicone hydrogel wearers. Optom Vis Sci 1999;76,12s:226.

Simpson T, Dumbleton K, Fonn D, Chong T. Multidimensional scaling of ocular discomfort by soft contact lenses. Optom Vis Sci 1999;76,12s:109.

Pritchard N, Fonn D. Myopia associated with extended wear of low-oxygen-transmissible hydrogel lenses. Optom Vis Sci 1999;76,12s:169.

du Toit R, Situ P, Fonn D. Ocular surface physiology and ocular irritation symptoms in a presbyopic population . Optom Vis Sci 1999;76,12s:109.

Simpson T, Lau J, Jones L, Richter D, Dumbleton K, Fonn D. Physical properties predict the dimensions of ocular discomfort of ophthalmic drops. Optom Vis Sci 1999;76,12s:237.

Situ P, Simpson T, Fonn D. Clinical measures do not discriminate symptomatic and asymptomatic contact lens wearers. Invest Ophthalmol Vis Sci 1999;40,4:s909.

du Toit R, Vega JA, Simpson TL, Fonn D. Corneal temperature variation over 24 hours. Invest Ophthalmol Vis Sci 1999;40,4:s979.

Dumbleton KA, Richter DB, Fonn D, Chalmers R. Hypoxic effects on ocular hyperemia and neovascularization in extended wear. Contact Lens & Anterior Eye 1999;22,4:158.

Dumbleton KA, Richter DB, Fonn D, Chalmers R. Refractive error and corneal curvature changes associated with hypoxia. Contact Lens & Anterior Eye 1999;22,4:147.

Fonn D. Does overnight unilateral contact lens wear induce a sympathetic effect on the contralateral eye?. Debate – “Practitioner reluctance to prescribe extended wear will not limit its use” British Contact Lens Association, Birmingham, United Kingdom, 1999.

Fonn D. Refractive changes with high and low Dk hydrogel lenses. International Society for Contact Lens Research, Phuket, Thailand, 1999.

Fonn D. Refractive development of the eye. International Agency for Prevention of Blindness – The Right to Sight Conference, Beijing, China, 1999.

1998

Dumbleton K, Richter D, Simpson T, Fonn D, Chalmers R. A comparison of the vascular response to extended wear of conventional lower Dk and experimental high Dk hydrogel contact lenses. Optom Vis Sci 1998;75,12s:170.

du Toit R, Vega JA, Simpson TL, Fonn D. Diurnal variation of corneal thickness, sensitivity and temperature. Optom Vis Sci 1998;75,12s:82.

Chan AA, Simpson TL, du Toit R, Fonn D. Glare shadow test: evaluation of a novel glare-halo test. Optom Vis Sci 1998;75,12s:171.

Bahoshy LP, Simpson TL, Situ P, Fonn D. In vivo contact lens drying reduces contrast sensitivity and increases measurement variability. Optom Vis Sci 1998;75,12s:169.

Simpson T, Fonn D, Orsborn G. Measuring ocular discomfort: metric scaling of typical analogue scores reveals at least 2 dismensions of discomfort of ophthalmic drops. Optom Vis Sci 1998;75,12s:67.

Simpson T, Chan A, Fonn D. Measuring ocular redness: first order (luminance and chromaticity) measurements provide more information than second order (spatial structure) measurements. Optom Vis Sci 1998;75,12s:279.

Pritchard N, Fonn D. Prevalence of “clear” corneas in potential clinical trial participants. Optom Vis Sci 1998;75,12s:161.

Dumbleton K, Richter D, Fonn D, Chalmers R. Refractive and keratometric changes following extended wear. Optom Vis Sci 1998;75,12s:170.

Sorbara L, Chong T, Higazy MT, Fonn D. Visual acuity of keratoconic eyes as a function of RGP contact lens base curves. Optom Vis Sci 1998;75,12s:173.

Fonn D, du Toit R, Vega JA, Simpson TL, Chalmers R. Apparent sympathetic response of contralateral nonlens wearing eyes after overnight lens wear in the fellow eye. Invest Ophthalmol Vis Sci 1998;39,4:s336.

du Toit R, Fonn D, Simpson TL. Recovery from hyperemia after overnight wear of hydrogel lenses. Invest Ophthalmol Vis Sci 1998;39,4:s336.

Fonn D, du Toit R, Vega JA, Simpson T. Apparent sympathetic response of the contralateral non-lens wearing eyes after overnight contact lens wear in the fellow eye. Fourth Biomedical Optics and Implant Colloquim, Bascom Palmer Eye Institute, University of Miami, Florida, 1998.

1997

Elliott M, Fandrich H, Simpson TL, Fonn D. Analysis of tear break-up time measurement techniques. Optom Vis Sci 1997;74,12s:191.

Simpson TL, Higazy M, Fonn D. Corneal and conjunctival sensitivity: A comparison of the non-contact air puff and the Cochet-Bonnet esthesiometers. Optom Vis Sci 1997;74,12s:20.

du Toit R, Simpson TL, Fonn D. Factor analysis of symptoms of soft contact lens wearers. Optom Vis Sci 1997;74,12s:201.

Fonn D, Vega JA, du Toit R, Simpson TL. High DK versus approved 7-day extended wear hydrogel lenses: The overnight corneal swelling response. Optom Vis Sci 1997;74,12s:76.

Dumbleton KA, Simpson TL, Richter DB, Fonn D, Orsborn G, Bolanowski SJ. Multidimensional scaling of ocular comfort in symptomatic “dry eye” post menopausal women. Optom Vis Sci 1997;74,12s:188.

Simpson TL, Richter DB, Dumbleton KA, Fonn D, Orsborn G, Bolanowski SJ. Multidimensional scaling of ocular discomfort induced by ophthalmic drops. Optom Vis Sci 1997;74,12s:187.

Situ P, Fonn D, Pritchard N. Subjective responses of symptomatic and asymptomatic hydrogel contact lens wearers. Optom Vis Sci 1997;74,12s:202.

Dumbleton KA, Fonn D, Richter DB. The influence of a UV blocking filter on the comfort and performance of an extended wear lens. Optom Vis Sci 1997;74,12s:196.

Vega JA, Simpson TL, Fonn D. The measurement of ocular surface sensitivity using a noncontact esthesiometer. Optom Vis Sci 1997;74,12s:103.

Situ P, Fonn D, Pritchard N, Simpson TL. Dryness, comfort levels and lens dehydration in symptomatic and asymptomatic hydrogel lens wearers. Invest Ophthalmol Vis Sci 1997;38,4:s135.

Fonn D, Situ P, Pritchard N. The incidence of corneal infiltrates and ulcers in daily and extended wear clinical trials. Invest Ophthalmol Vis Sci 1997;38,4:s136.

1996

Chong T, Simpson T, Pritchard N, Dumbleton K, Richter D, Fonn D. Clinical grading scales: Continuous vs. discrete. Optom Vis Sci 1996;73,12s:.

Simpson TL, Vega JA, Fonn D, Patil S. Corneal temperature and sensitivity measured using noncontact devices. Optom Vis Sci 1996;73,12s:67.

Sorbara L, Fonn D, Chong T. Evaluation and comparison of videokeratoscopic simulated fluorescein programs. Optom Vis Sci 1996;73,12s:223.

Vega JA, Simpson TL, Fonn D, Patil S. Noninvasive assessment of corneal sensitivity: A preliminary report. Optom Vis Sci 1996;73,12s:104.

Chong T, Simpson TL, Pritchard N, Dumbleton KA, Richter DB, Fonn D. Repeatability of discrete and continuous clinical grading scales. Optom Vis Sci 1996;73,12s:232.

Gschwind KP, Simpson TL, Richter DB, Fonn D. The effect of increasing monocular defocus on interocular suppression scotoma diameter. Optom Vis Sci 1996;73,12s:139.

Simpson TL, Richter DB, Fonn D. Adaptation to uniocular blur in monovision. Invest Ophthalmol Vis Sci 1996;37,3s:75.

Fonn D, Richter DB, Pritchard N, Simpson TL. Effects of hypoxic stress on post-PRK corneas. Invest Ophthalmol Vis Sci 1996;37,3s:61.

Dumbleton KA, Simpson TL, Sorbara L, Fonn D, Lennox B. Ocular comfort measurements of neophyte contact lens wearers. Invest Ophthalmol Vis Sci 1996;37,3:s72.

Caffery B, Richter D, Simpson T, Fonn D, Doughty M, Gordon K. The prevalence of dry eye in contact lens wearers: Part 2 of the Canadian dry eye epidemiology study (CANDEES). Invest Ophthalmol Vis Sci 1996;37,3s:72.

1995

Fonn D. Continuous wear - session 5. Transactions of ht ISCLR symposium (Jackson Hole, Wyoming), 1995.

Fonn D, Pritchard N, Brazeau D, Michaud L, GEQCLC. Discontinuation of contact lens wear : The numbers, reasons and patient profiles. Invest Ophthalmol Vis Sci 1995;36,4:s312.

Pritchard N, Fonn D. Postlens tear debris during extended wear of hydrogels. Optom Vis Sci 1995;72,12s:149.

Gschwind KP, Pritchard N, Simpson TL, Cox I, Fonn D. Repeatability of a computer assisted VA test. Optom Vis Sci 1995;72,12s:121.

Doughty MJ, Fonn D, Caffery B, Gordon K, Richter D, Simpson TL. The Canadian dry eye epidemiology study (CANDEES): A first report. Optom Vis Sci 1995;72,12s:154.

Simpson TL, Richter D, Dumbleton K, Fonn D. The repeatability of a new clinical test of interocular suppression of uniocular blur. Optom Vis Sci 1995;72,12s:86.

Fonn D. Continuous wear of hydrogel contact lens - the potential for increasing the success rate of contact lens wear. American Academy of Optometry - Symposium of the Cornea and CL Section, 1995.

McDonald KE, Fonn D, Richter D, Robboy M. Comparsion of the physiological response to extended wear of an experimental high DK soft lens versus a 38% hema lens. Invest Ophthalmol Vis Sci 1995;36,4:s310.

Sivak JG, Herbert KL, Fonn D. In vitro ocular irritancy measures of four contact lens solutions - damage and recovery. Invest Ophthalmol Vis Sci 1995;36,4:s311.

Zheng P, Campbell MCW, Fonn D. Measurement of retinal image quality variation with asphericity and decentrarion of contact lenses. Invest Ophthalmol Vis Sci 1995;36,4:s939.

1994

Butuner Z, Fonn D, Ellis E, Leahy C. Rigid contact lens wettability: The relationship of in vivo and in vitro testing. Optom Vis Sci 1994;71,12s:133.

Carroll EA, Guillon M, Fonn D, Guillon J-P, Leahy CD. Effect of polymeric composition on the in vivo wettability of RGP contact lenses. Invest Ophthalmol Vis Sci 1994;35,4:1178.

Potvin RJ, Fonn D, Sorbara L. Measurement of polycarbonate aspheres with corneal topography systems. Invest Ophthalmol Vis Sci 1994;35,4:2194.

Doughty MJ, Potvin R, Pritchard N, Fonn D. Quantitative morphometric analyses of the size and shape of fluorescein-highlighted patterns of the human tarsal conjunctiva. Invest Ophthalmol Vis Sci 1994;35,4:1796.

Butuner Z, Leahy C, Ellis E, Fonn D. Repeatability of non invasive tear film structure and stability assessment in three groups of subjects. Invest Ophthalmol Vis Sci 1994;35,4:1690.

1993

Sorbara L, Fonn D, Holden BA, Wong R. A comparison of the performance of “centred” vs “upper-lid” attached rigid gas permeable lenses. Optom Vis Sci 1993;70,12s:18.

Butuner Z, Arnal R, Fonn D. Comparison of two measurement methods of in vivo contact lens movement. Optom Vis Sci 1993;70,12s:77.

Skaff A, Cullen AP, Doughty M, Fonn D. Contact lens induced corneal swelling in young adult insulin dependent diabetics. Optom Vis Sci 1993;70,12s:49.

Weed K, Fonn D, Potvin R. Discontinuation of contact lens wear. Optom Vis Sci 1993;70,12s:140.

Fonn D, Pritchard N, Weed K, Potvin R, Arnal R, Lennox B. Frequent replacement of soft contact lenses reduces complications: 2 year results. Optom Vis Sci 1993;70,12s:121.

Holden BA, Fonn D, Sulaiman S, Sweeney D. International optometric education: The need for an integrated international program. Optom Vis Sci 1993;70,12s:59.

Pritchard N, Fonn D. In vivo soft lens dehydration, movement and diameter characteristics and dryness symptoms. Invest Ophthalmol Vis Sci 1993;34,4:1008.

Potvin R, Fonn D, Sorbara L. Topographic keratography modelling systems: Numbers behind the graphics. Invest Ophthalmol Vis Sci 1993;34,4:1252.

1992

Fonn D, Pritchard N, Weed K, Potvin R. Ocular responses associated with frequently replaced and non-replaced hydrogel lenses. Optom Vis Sci 1992;69,12s:26.

Williams-Lyn D, MacNeill K, Fonn D. Parameter alterations can affect comfort of rigid gas permeable lenses. Optom Vis Sci 1992;69,12s:152.

Elliott DB, Fonn D, Flanagan J. The relative sensitivity of various clinical tests to contact lens induced corneal oedema. Optom Vis Sci 1992;69,12s:43.

Sorbara L, Fonn D, Holden BA, Wong R. Factors affecting rigid gas permeable vertical lens decentration. Optom Vis Sci 1992;69,12s:153.

1991

Fonn D, Davids L, Garnett B, Gauthier C, Pritchard N. Palpebral aperture size of contact lens wearers and non-contact lens wearers. Optom Vis Sci 1991;68,12s:146.

Gauthier C, Fonn D, Pritchard N. Patient preferences and comparative ocular responses to rigid and soft contact lenses. Optom Vis Sci 1991;68,12s:145.

Sorbara L, MacNeill K, Fonn D. Effect of RGP lens flexure on vision. Invest Ophthalmol Vis Sci 1991;32,4:731.

Fonn D, Sorbara L, Dumbleton K, Gauthier C, MacNeill K. Adverse responses to a chlorhexidine tablet disinfection system. Invest Ophthalmol Vis Sci 1991;32,4:738.

Fonn D, Dumbleton K, Sorbara L, Hrynchak P. Comparative clinical performance of three RGP materials. CLAO J 1991Supp..

1990

Dumbleton K, Fonn D, Hrynchak P, Davids L. Deposit resistance of RGP materials. Optom Vis Sci 1990;67,10:138.

Fonn D, Gauthier C. Dynamic and static fluorescein pattern evaluation of a biaspheric back surface rigid lens design. Optom Vis Sci 1990;67,10:139.

Callender M, Gauthier C, Charles A, Fonn D, Davids L. Evaluation of Aquasteril: A contact lens cleaning and disinfecting unit. Optom Vis Sci 1990;67,10:71.

Fonn D, Gauthier C. Lens diameter and its effect on rigid lens comfort. Optom Vis Sci 1990;67,10:45.

Fonn D. Ptosis in contact lens wearers. International Society for Contact Lens Research The 6th Biannual Conference, 1990.

1989

Hrynchak P, Dumbleton K, Davids L, Fonn D. Base curve stability and durability of rigid gas permeable lenses. Optom Vis Sci 1989;66,10:169.

MacNeill K, Gauthier C, Fonn D. Comparison of two automated refractors and keratometers with traditional subjective techniques. Optom Vis Sci 1989;66,10:141.

Sorbara L, Dumbleton K, Fonn D, Hrynchak P. Daily wear of an extended wear fluorosilicone acrylate material. Optom Vis Sci 1989;66,10:165.

Fonn D, Gauthier C, Sorbara L. In eye wettability of rigid contact lenses. Optom Vis Sci 1989;66,10:164.

Davids L, Dobson A, Fonn D, Callender M. Measurement of soft contact lens base curves by an ultrasonic test unit. Optom Vis Sci 1989;66,10:96.

Fonn D, Gauthier C, Hrynchak P. Superficial fibrillary lines of the cornea. Optom Vis Sci 1989;66,10:239.

Fonn D, Sorbara L, Gautheir C. Permeability of rigid lenses: the higher the better?. European Research Symposium Edinburgh, 1989. [ Show Abstract ]

(Poster)

1988

Fonn D. In-eye wettability of rigid lenses. International Society for Contact Lens Research The 5th Biannual Conference, 1988.

Fonn D, Sorbara L, Gauthier C, Dumbleton K. In-vivo wetting of RGP lenses. International Society for Contact Lens Research (Kauai), 1988.

Fonn D, Sorbara L, Dumbleton K. Comparative fitting characteristics of aspheric and spherical design rigid gas permeable lenses. Am J Optom Physiol Opt 1988;65,10:131.

Fonn D, Sorbara L, Dumbleton KA. Comparative fitting characteristics of aspheric and spherical design rigid gas permeable lenses. Research Symposium on Contact Lenses (Berlin) 1988.

1987

Fonn D. The clinical performance of high DK rigid gas permeable lenses used for extended wear. Am J Optom Physiol Opt 1987;64,10:6.

Callendar MGE, Fonn D. Comparing the overnight corneal swelling response of collagen contact lenses with other extended wear hydrophilic lenses. Am J Optom Physiol Opt 1987;64,10:22.

1986

Fonn D. Soft contact lens induced edema at high altitude. Am J Optom Physiol Opt 1986;63,10:131.

Fonn D. Comparing overnight contact lens induced corneal swelling and deswelling with 6 hours patched eye response. Am J Optom Physiol Opt 1986;63,10:131p.

Professional Publications

2013

Fonn D. Clinical relevance of contact lens lubricity. Contact Lens Spectrum 2013;28(13).

Fonn D. Assessing end of day comfort . Contact lens Spectrum 2013;28(7).

Woods J, Woods C, Fonn D, Jones L. Potential acceptance of a daily disposable silicone hydrogel multifocal lens in emmetropic presbyopes. Optom Vis Sci 2013;88: E-Abstract 135100.

2010

Dumbleton K, Woods C, Jones L, Fonn D. How compliant are today’s lens wearers?. Contact Lens Spectrum 2010;25,6:34-37.

Richter D, Dumbleton K, Guthrie S, Woods C, Jones L, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement in Canada. Canadian Journal of Optometry 2010;72,1:10-19.

2009

Woods J, Woods CA, Fonn D. Managing the emerging presbyopic contact lens wearer. Optometry Today 2009;49,12:32-35.

Woods J, Woods C, Fonn D. Practical guide for fitting soft centre near design multifocal contact lenses. Contact Lens Spectrum 2009.

2006

Fonn D, Dumbleton K, Sivak A. Benefits of silicone hydrogel lenses. Contact Lens Spectrum 2006;21,2s:38-44.

Sweeney D, Fonn D, Evans K. Silicone hydrogels: the evolution of a revolution. Contact Lens Spectrum 2006;21,2s:14-19.

Fonn D, Kerby K, Simpson T, Bitton E, Rajani N, Jones L, Berthiaume L, Miranda T, Caffrey B, Lutzi D, Maroun F, Leinweber G. Round table discussion on dry eye. Can J Optom 2006;68,5:189-200.

Fonn D. 10 contact lens highlights from the last two decades . Contact Lens Spectrum 2006;21,6:48.

Fonn D. Silicone hydrogels - making the choice. Optician 2006;232,6067:22-24.

Fonn D. Ten contact lens highlights from the last two decades. Contact Lens Spectrum 2006;21,6:48.

Fonn D, Dumbleton K, Jalbert I, Sivak A. Benefits of silicone hydrogel lenses. Contact Lens Spectrum 2006;21,2s:38-44.

Fonn D. Silicone hydrogels - making the choice. The Optician 2006;232,6063:22-24.

Sweeney D, Fonn D, Evans K. Silicone hydrogels: the evolution of a revolution. Contact Lens Spectrum 2006;21,2:28-38.

2005

Fonn D, Dumbleton K, Papas E. Conjunctival appearance related to silicone hydrogel lens wear. Contact Lens Spectrum 2005;20,9:46.

Fonn D, Sivak A. Benefits and challenges of high-Dk/t materials. Contact Lens Spectrum 2005;20,2:28-31.

Fonn D, Holden B, Bonanno JA, Cavanagh D. O2 measurement and needs. Contact Lens Spectrum 2005;20,8s:12-15.

Fonn D, Holden B, Hill R, Cavanagh D, Wilson GS. Achieving normoxia. Contact Lens Spectrum 2005;20,8s:4-7.

Fonn D, Sweeney D, Holden B, Hill R, Papas E, Cavanagh D. Measuring oxygen uptake. Contact Lens Spectrum 2005;20,8s:8-9.

Fonn D, Papas E, Cavanagh D, Wilson GS. Sustaining limbal health. Contact Lens Spectrum 2005;20,8s:10-11.

Fonn D, Holden B, Bonanno JA, Cavanagh D. 0 2 measurements and needs. Contact Lens Spectrum 2005;20,8s:12-15.

2004

Moezzi A, Fonn D. Corneal thickness measurement. Contact Lens Spectrum 2004.

Fonn D. On the importance of silicone hydrogel contact lenses. Refractive Eyecare for Opthalmologists 2004;8,10:11-14.

2002

du Toit R, Sweeney D, Fonn D, Stern J. Managing silicone hydrogel complications. Contact Lens Spectrum 2002;17,5:34-40.

Fonn D, du Toit R, Sweeney D. Managing silicone hydrogel complications. Review of Contact Lenses 2002;7,July:18-20.

Fonn D. Preventing contact lens dropouts. Contact Lens Spectrum 2002;17,8:26-32.

Fonn D, Dumbleton K, Jones L, du Toit R, Sweeney D. Silicone hydrogel material and surface properties. Contact Lens Spectrum 2002;17,3:24-28.

Fonn D. Observations of corneal staining with MPS and silicone hydrogel lenses. Contact Lens Spectrum 2002;17,11:32.

2000

Fonn D. Silicone hydrogel website - resource for practitioners. Int Contact Lens Clin 2000;27188-190.

Sweeney D, Fonn D, Guillon M. Silicone hydrogels - clinical performance, factors affecting success and tear exchange - multiple-choice answers. Optician 2000;219,5733:16.

1999

Fonn D. Factors affecting the success of silicone hydrogels. Optician 1999;218,5730:27-29.

1998

Higazy MT, Fonn D, Sorbara L. Rigid gas permeable contact lens fitting in keratoconus. Bull Ophthalmol Soc Egypt 1998;91,6:985-988.

1996

Fonn D. Discontinuation of contact lens wear and its effect on the growth of the business. Contact Lens Spectrum 1996;11,9:4s-5s.

Potvin RJ, Fonn D, Sorbara L. In vivo comparison of corneal topography and keratometry systems. Int Contact Lens Clin 1996;23,1:20-26.

1993

Williams-Lyn D, MacNeill K, Fonn D. The effect of rigid lens back optic zone radius and diameter changes on comfort. Int Contact Lens Clin 1993;20,11/12:223-229.

1992

Efron N, Henriquez A, Merkx JTM, Alfonso E, Bouron P, Fonn D, Nishida T, Ostlund K, Schnider CM, Tan KC. Contact lens maintenance systems. Int Contact Lens Clin 1992;19,7/8:153-156.

Holden B, Fonn D, Sweeney D, Gauthier C, Sorbara L, Efron N. International Association of Contact Lens Educators expands globally. Int Contact Lens Clin 1992;19,7/8:174-181.

Efron N, Henriquez A, Merkx JTM, Alfonso E, Bouron P, Fonn D, Nishida T, Ostlund K, Schnider CM, Tan KC. Why fit contact lenses?. Optician 1992;204,5367:12-14.

Efron N, Henriquez A, Merkx JTM, Alfonso E, Bouron P, Fonn D, Nishida T, Ostlund K, Schnider CM, Tan KC. Why wear contact lenses?. Optician 1992;204,5371:23-24.

Efron N, Henriquez A, Merkx J, Alfonso E, Bouron P, Fonn D, Nishida T, Ostlund K, Schnider CM, Tan KC. A discussion paper on contact lens maintenance systems. Optician 1992;204,5358:16-20.

1991

Efron N, Henriquez A, Merkx JTM, Alfonso E, Bouron P, Fonn D, Nishida T, Ostlund K, Schnider CM, Sweeney DF, Tan KC. Disposable contact lenses. Int Contact Lens Clin 1991;18,7/8:127-129.

Cox I, Fonn D. Interference filters to eliminate the surface reflex and improve contrast during fluroescein photography. Int Contact Lens Clin 1991;18,9/10:178-181.

Fonn D. Presbyopia and the contact lens wearer. Vista 50 Plus 1991,Spring:.

1990

Fonn D, Gauthier C, Sorbara L. Adverse response rates in concurrent short-term extended wear and daily wear clinical trials of hydrogel lenses. Int Contact Lens Clin 1990;17,9/10:217-223.

Fonn D, Gauthier C. Aftercare of RGP lens wearers . Contact Lens Spectrum 1990;5,9:71-81.

1982

Fonn D. South Africa: Low status for vision care. Contact Lens Forum 1982;7,7:45-53.

Books

2010

Sorbara L, Fonn D, Woods C, Sivak A, Boshart B. Correction of Keratoconus with GP Contact Lenses. Bausch and Lomb. 2010.

2009

Williams L, Sorbara L. Care and Maintenance of GP lenses. In: The IACLE Contact Lens Course, ed. Fonn D. IACLE. 2009.

Fonn D (ed.). The IACLE Contact Lens Course. IACLE. 2009.

2007

Sorbara L, Fonn D, Woods C, Sivak A, Boshart B. Correction of Presbyopia with GP Contact Lenses. Bausch and Lomb. 2007.

Sweeney D, Stretton S, Fonn D, Swarbrick HA, Holden BA. Extended and continuous wear lenses. In: Contact Lenses (5th Edition), ed. Phillips AJ, Speedwell L, Morris,J. Butterworth-Heinemann. 2007.

2005

Brennan N, Fonn D. The Physiological Effects of Hypoxia on the Anterior Eye. In: Silicone Hydrogels 2nd Edition , ed. Sweeney D. Butterworth-Heinemann. 2005.

2004

Fonn D, Sorbara L. Progress Evaluation Procedures. In: Clinical Contact Lens Practice (2nd Edition), ed. Bennett ES, Weissman BA. Lippincott Williams and Wilkens. 2004.

Fonn D and Sorbara L. Problem Solving. In: Clinical Contact Lens Practice (2nd Edition), ed. ES Bennett and BA Weissman. J.B. Lippincott. 2004.

Brennan N, Fonn D. Corneal Hypoxia. In: Silicone hydrogels: Continuous-wear contact lenses, ed. Sweeney, DF. Butterworth-Heinemann. 2004.

2000

Fonn D, Pritchard N, Dumbleton K. Factors affecting the success of silicone hydrogels. In: Silicone hydrogels: The rebirth of continuous wear contact lenses, ed. Sweeney DF. Butterworth Heinemann. 2000.

1991

Fonn D. Progress Evaluation Procedures. In: Clinical Contact Lens Practice, ed. Bennett ES, Weissman BA. J.B. Lippincott. 1991.