Muntz,A., Subbaraman,L. N., Sorbara,L., Jones,L. Tear exchange and contact lenses: A review. Journal of Optometry 2015;8,1:2-11. [ Show Abstract ]
Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses.
Duench,S., Sorbara,L., Keir,N., Simpson,T., Jones,L. Impact of silicone hydrogel lenses and solutions on corneal epithelial permeability. Optometry and Vision Science 2013;90,6:546-556. [ Show Abstract ]
PURPOSE: The primary purpose of this pilot study was to compare epithelial barrier function (EBF) and staining in a small group of participants using a silicone hydrogel (SH) lens worn on a daily basis with two different care regimens. Secondarily, the aim was to see if there was any correlation between corneal staining and EBF. METHODS: The corneal EBF of 10 non-lens wearers (control) and 15 age-matched asymptomatic SH contact lens wearers (test) were assessed using fluorophotometry. Biomicroscopy was performed to assess corneal staining after the EBF was measured. The lens wearers wore PureVision (FDA group V) SH lenses for two consecutive 1-month periods while using either Alcon Opti-Free Express or Renu Fresh using a randomized, investigator-masked, crossover design. Control subjects were assessed on one occasion, and lens wearers were examined before fitting with lenses and after 7, 14, and 28 days of lens wear, with each combination. RESULTS: Compared with the control group, both study groups had an increase in epithelial permeability at baseline (p = 0.04). There were no changes in EBF during the treatment period for either solution (p = 0.87). A significant difference in EBF was found between the test groups during the treatment period (p = 0.02), with greater permeability in the Renu Fresh-disinfected lenses. There was poor correlation between corneal staining and EBF (r = 0.35, p > 0.05) because of large individual variations. CONCLUSIONS: Daily wear of highly oxygen-permeable SH lenses increases corneal epithelial permeability to fluorescein probably because of increased mechanical effects. In addition, certain lens-solution interactions can add to this effect, as seen in this study. Despite having a low amount of central corneal staining in the Renu Fresh group, staining and EBF did not prove to be well correlated. The presence of central corneal staining is a confounding factor when measuring EBF. Copyright © 2013 American Academy of Optometry.
Srinivasan,S., Menzies,K. L., Sorbara,L., Jones,L. W. Imaging meibomian glands on a patient with chalazia in the upper and lower lids: A case report. Contact Lens and Anterior Eye 2013;36,4:199-203. [ Show Abstract ]
Aim: To describe the meibomian gland (MG) appearance in a case of eyelid chalazia, using a novel meibography method. Methods: A 29-year-old female of South Asian origin presented with mild swelling in the lower lid of the left eye. The patient also presented with a history of a recurrent chalazion in the upper lid of the same eye, which later progressed to an active chalazion. A chalazion also developed in the upper lid of the right eye. Meibography was performed using a novel Keratograph (Keratograph 4, OCULUS, Wetzlar, Germany) to evaluate the structure of the MG in the area affected by the chalazia. Results: The area of the recurrent chalazion in the upper left lid showed partial and/or complete MG loss. The active chalazia in the lower left lid and the upper right lid showed inflammation and MG drop out at the affected site. The inflammation was found to be reduced during the follow-up visits, however disappearance of MG very specific to the region of the chalazion was observed. Conclusion: The Keratograph 4 was able to image the MG structures clearly, allowing the clinician to monitor the progression of chalazia and the MG loss in the affected areas. © 2013 British Contact Lens Association.
Srinivasan,S., Menzies,K., Sorbara,L., Jones,L. Infrared imaging of meibomian gland structure using a novel keratograph. Optometry and Vision Science 2012;89,5:788-794. [ Show Abstract ]
PURPOSE.: To examine the ability of a novel non-contact device (Keratograph 4) to image the meibomian gland (MG) structures and their morphological changes in the upper and lower eyelids. METHODS.: Thirty-seven participants (mean age 57.8 ± 8.5 years; 3 males and 34 females) completed the Ocular Surface Disease Index questionnaire to assess dryness symptoms. Meibum secretion quality score, number of blocked gland orifices, and meibum expressibility scores were assessed. The lower lid (LL) and upper lid (UL) of all subjects were everted and images of the MGs were taken using the Keratograph 4 (OCULUS). A MG dropout score (MGDS) due to complete or partial gland loss of both lids was obtained using a subjective 4-grade scoring system, and digital analysis of the images using ImageJ was performed. Presence of tortuosity and visible acinar changes of the MGs were also noted. RESULTS.: MGDS for both lids was significantly positively correlated with the Ocular Surface Disease Index score (r = 0.51; p < 0.05). The MGDS determined using the digital grading was also significantly positively correlated (UL: r = 0.68, p < 0.05; LL: r = 0.42, p < 0.05). The sum of the MGDS for both lids using the subjective grading scale was significantly different between the non-MGD and MGD group (1.3 ± 1.0 vs. 3.1 ± 1.1; p = 0.0004). MGDS assessment using the digital grading was significantly different between non-MGD (UL = 6%, LL = 8%) and MGD group (UL = 32%, LL = 42%; p = 0.001). Tortuous MG was observed only on the UL in 6% of the participants. Visible acinar changes were noted in 40% of the study participants. CONCLUSIONS.: Infrared meibography is now possible in a clinical setting using commercially available devices, and meibography can help determine differences in MG structure in subjects symptomatic of dry eye. Copyright © 2012 American Academy of Optometry.
Dalton,K., Sorbara,L. Fitting an MSD (Mini Scleral Design) rigid contact lens in advanced keratoconus with INTACS. Contact Lens and Anterior Eye 2011;34,6:274-281.
Maram,J., Sorbara,L., Simpson,T. Accuracy of Visante and Zeiss-Humphrey Optical Coherence Tomographers and their cross calibration with optical pachymetry and physical references. Journal of Optometry 2011;4,4:147-155.
Sorbara,L., Maram,J., Bizheva,K., Hutchings,N., Simpson,T. L. Case report: Chalazion and its features visualized by ultrahigh resolution optical coherence tomography. Contact Lens and Anterior Eye 2011;34,2:87-91.
Dalton,K., Schneider,S., Sorbara,L., Jones,L. Confocal microscopy and optical coherence tomography imaging of hereditary granular dystrophy. Contact Lens and Anterior Eye 2010;33,1:33-40.
Sorbara,L., Dalton,K. The use of video-keratoscopy in predicting contact lens parameters for keratoconic fitting. Contact Lens and Anterior Eye 2010;33,3:112-118.
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.
Sorbara,L., Jones,L., Williams-Lyn,D. Contact lens induced papillary conjunctivitis with silicone hydrogel lenses. Contact Lens and Anterior Eye 2009;32,2:93-96. [ Show Abstract ]
PURPOSE: To describe the refitting of a soft lens wearer into a silicone hydrogel lens due to neovascularization. This change, in turn, caused contact lens induced papillary conjunctivitis (CLPC) and a further refitting was necessary. METHODS: The patient was refit into a high Dk surface treated silicone hydrogel with a high modulus value. A second refitting was undertaken into a lower Dk silicone hydrogel contact lens with a lower modulus value which had no surface treatment but incorporated an internal wetting agent. RESULTS: A high Dk/t lens was used to resolve existing neovascularization and chronic hyperaemia. Subsequently, CLPC response occurred, possibly due to a combination of factors, resulting in irritation of the palpebral conjunctiva. This resulted in temporary lens discontinuation. A second silicone hydrogel lens was fit, along with the use of a non-preserved care system, which led to improvement and eventual resolution of the condition. CONCLUSION: High Dk silicone hydrogel lenses have shown excellent efficacy in resolving hypoxic complications such as neovascularization and hyperaemia. However, attention needs to be paid to their potential effect on the upper tarsal plate. More than one silicone hydrogel lens may be needed to help resolve these issues.
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.
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.
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.
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.
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.
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.
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.
Jones,L., Macdougall,N., Sorbara,L. G. Asymptomatic corneal staining associated with the use of balafilcon silicone-hydrogel contact lenses disinfected with a polyaminopropyl biguanide-preserved care regimen. Optometry and Vision Science 2002;79,12:753-761. [ Show Abstract ]
PURPOSE: To compare subjective symptoms and signs in a group of individuals who wear silicone-hydrogel lenses on a daily wear basis while they sequentially used two differing care regimens. METHODS: Fifty adapted soft-lens wearers were fitted with a silicone-hydrogel lens material (PureVision, Bausch & Lomb). The lenses were worn on a daily wear basis for two consecutive 1-month periods, during which the subjects used either a Polyquad (polyquaternium-1) -based system or a polyaminopropyl biguanide (PHMB) -based system, using a double-masked, randomized, crossover experimental design. RESULTS: Significant levels of relatively asymptomatic corneal staining were observed when subjects used the PHMB-based system, with 37% of subjects demonstrating a level of staining consistent with a classical solution-based toxicity reaction. Only 2% of the subjects exhibited such staining when using the Polyquad-based system. These results were significantly different (p < 0.001). Significant symptoms were not correlated with the degree of staining, with no differences in lens comfort or overall preference being reported between the regimens (p = NS). The only statistically significant difference in symptoms related to minor differences in stinging after lens insertion being reported, with the Polyquad-based system demonstrating less stinging (p < 0.008). CONCLUSIONS: Practitioners who fit silicone-hydrogel contact lenses on a daily wear basis should be wary of the potential for certain PHMB-containing multipurpose care systems to invoke corneal staining. Switching to non-PHMB based regimens will eliminate this complication in most instances.
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.
Mathur,A., Jones,L., Sorbara,L. Use of reverse geometry rigid gas permeable contact lenses in the management of the postradial keratotomy patient: Review and case report. International Contact Lens Clinic 1999;26,5:121. [ Show Abstract ]
Radial keratotomy (RK) is a well-known procedure for reducing myopia. However, the complications associated with the procedure and the development of newer technologies, such as photorefractive keratectomy and laser-assisted in situ keratomileusis, has resulted in the technique of RK falling out of favor. A number of patients who received RK during the 1980s are now experiencing a shift in their prescription and are presenting to primary care practitioners for contact lens fitting. These patients pose a significant challenge to the contact lens practitioner, and novel methods frequently are required to fit corneas that exhibit such abnormal topography. This article reviews the potential problems associated with fitting patients who have received RK and describes a case in which a novel lens design was used to achieve a successful lens fit.
Sorbara,L., Richter,D., Chong,T. Evaluation and comparison of videokeratoscopic simulated fluorescein programs. 1998;60,3:158-163. [ Show Abstract ]
Software for designing rigid gas permeable contact lenses has been developed for a number of corneal topography systems. There are some common and some unique features in the fitting programs of these instruments. Three currently available instruments are compared and contrasted to traditional contact lens fitting. These instruments are the EyeSys (EyeSys Technologies), the EyeMap (Alcon) and the TMS (Computed Anatomy, Tomey).
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).
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.
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.
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.
Sorbara,L., Talsky,C. Contact lens wear in the dry eye patient predicting succes and achieving it
. Canadian Journal of Optometry 1988;50,4:234-241. [ Show Abstract ]
Clinical diagnosis of dry eye and its implications in successful contact lens wear has not been well defined. Two thousand patient files from the University of Waterloo, School of Optometry, Contact Lens Clinic were surveyed and 54 patients, diagnosed as having dry eye, were fit with contact lenses and were included in a retrospective prevalence study. Diagnostic procedures commonly used in the detection of dry eye were evaluated in terms of their ability to accurately predict successful lens wear in the dry eye patient. The Tear Break Up Time was found to be the most valid in identifying those patients who are less likely to achieve success. Schirmer`s Test was found to be of little predictive value. Possible correlations between lens type and successful lens wear were investigated. Dry eye patients fit with low water content, thin (0.06-0.10 mm) hydrogel lenses of differing water content or rigid gas permeable lenses. Additional factors which may serve to increase successful lens wear are briefly discussed.
Otchere H, Sorbara L, Jones L. Repeatability and accuracy of the Oculus Pentacam HR corneal topographer in measuring radius of curvature and shape factor. Global Specialty Lens Symposium, Las Vegas, USA, 2013.
Otchere H, Sorbara L, Jones L . Fitting semi-scleral contact lenses using corneal sagittal depth measurements and evaluation of visual acuity and comfort ratings. Optom Vis Sci 2013;90: E-Abstract 130968..
Srinivasan S, Menzies K, Sorbara L, Jones L. Infra-red Imaging Of Meibomian Gland Structure Using A Novel Keratograph. Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 591.
Srinivasan S, Menzies K, Sorbara L, Jones L. Non-contact meibography using a novel keratograph. Contact Lens & Anterior Eye 2012;35,S1:e31-e32.
Maram J, Sorbara L, Simpson T. Conjunctival effects and blood flow changes related to silicone hydrogel lens wear and their relationship with end of day comfort. Contact Lens & Anterior Eye 2012;35,S1:e19.
Sorbara L, Dalton K. Use of MSD mini-scleral lens for patient with INTACS: Case Report. GSLS, 2012.
Srinivasan S, Menzies K, Sorbara L, Jones LW. Appearance of meibomian gland structures imaged using a Keratograph. Global Specialty Lens Symposium, 2012.
Maram J, Simpson T, Sorbara L, Song ES, Hutchings N, Bizheva K. Lens edge artifact occurring when imaged with an ultra-high resolution optical coherence tomographer. ISCLR Meeting , 2011.
Sorbara L, Maram J, Mueller K. Use of the Visante™ OCT anterior segment image to measure the saggital depth of keratoconus corneae compared to normal's at a 15mm chord length. Contact Lens & Anterior Eye 2011;34,S1:S26.
Maram J, Simpson T, Sorbara L, Bizheva K, Song ES. An apparent imaging artifact occurring at the edge of a contact lens when imaged with OCT; The underlying tissue appears erroneously discontinuous. Invest Ophthalmol Vis Sci 2011;52: E-abstract 6540.
Sorbara L, Maram J, Mueller K. Use of the Visante™ OCT anterior segment image to measure the saggital depth of keratoconus corneae compared to normal's at their HVID. GSLS (Las Vegas, USA), 2011.
Srinivasan S, Menzies K, Sorbara L, Jones L. Imaging meibomian gland structures using the oculus keratograph. Optom Vis Sci 2011;87:E-abstract 110775.
Maram J, Simpson T, Sorbara L, Bizheva K. Anterior segment optical coherence tomography: Non-contact ultra high resolution imaging of contact lens edge profiles. Optom Vis Sci 2010;87:E-abstract 105330.
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.
Maram J, Sorbara L, Simpson T and Bizheva K. Anterior segment OCT: non-contact high and ultra high resolution imaging of contact lens edge profiles. Optom Vis Sci 2009;86:E-abstract 95641.
Maram J, Sorbara L, Simpson T and Bizheva K. Metrics of the average cornea: anterior segment imaging with Visante™ OCT. Optom Vis Sci 2009;86:E-abstract 95645.
Dalton K, Schneider S, Jones L, Sorbara L. OCT and confocal imaging techniques used in the evaluation of two cases of hereditary granular dystrophy. Contact Lens & Anterior Eye 2009;32,5:235.
Maram J, Sorbara L, Simpson T, Bizheva K. UHR-OCT imaging of profiles of silicone hydrogel lenses. Optom Vis Sci 2009;86:E-Abstract 95641.
Dalton K, Schneider S, Jones L, Sorbara L. Use of digital imaging in sisters with hereditary granular dystrophy. Optom Vis Sci 2008;85:E-abstract 85292.
Maram J, Sorbara L, Simpson TL. Calibration of the new Visante Optical Coherence Tomographer. Optom Vis Sci 2008;85:E-abstract 80013.
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.
Sorbara L. The use of videokeratoscopy in determining the back optic zone diameter and overall lens diameter for contact lenses for keratoconus. Global Keratoconus Meeting, 2007.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Jones L, Schickler J, Sorbara L, Dumbleton K, Keir N, Bayer S. Corneal staining with FDA group II and silicone hydrogel contact lens materials used with PHMB-based disinfection systems. 7th World Biomaterials Conference (Sydney, Australia), 2004.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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:.
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.
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.
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.
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.
Senchyna M, Jones L, Forbes I, May C, MacDougall N, Sorbara L. The influence of multipurpose care regimens in controlling lysozyme deposition on Etafilcon contact lenses. Optom Vis Sci 2001;78,12s:308.
Jones L, Louie D, Senchyna M, Dumbleton K, Sorbara L. A comparative evaluation of lysozyme deposition on Etafilcon & silicone-hydrogel contact lens materials. Optom Vis Sci 2000;77,12s:176.
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.
Robinson B, Sorbara L. Introducing evidence-based principals in clinical education. Optom Vis Sci 2000;77,12s:30.
Sorbara L, Robinson B, Luong J. The frequency of presentation of common contact lens complications in a teaching contact lens clinic. Optom Vis Sci 2000;77,12s:164.
Jones L, Louie D, Senchyna M, Dumbleton K, Sorbara L. A comparative evaluation of lysozyme deposition on Etafilcon & silicone-hydrogel contact lens materials. B&L ERS (Berlin, Germany), 2000.
Sorbara L, Luong J. Nomogram for fitting keratoconic eyes utilising computerised video-keratoscopy. Optom Vis Sci 1999;76,12s:54.
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.
Sorbara L, Fonn D, Chong T. Evaluation and comparison of videokeratoscopic simulated fluorescein programs. Optom Vis Sci 1996;73,12s:223.
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.
Potvin RJ, Fonn D, Sorbara L. Measurement of polycarbonate aspheres with corneal topography systems. Invest Ophthalmol Vis Sci 1994;35,4:2194.
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.
Potvin R, Fonn D, Sorbara L. Topographic keratography modelling systems: Numbers behind the graphics. Invest Ophthalmol Vis Sci 1993;34,4:1252.
Sorbara L, Fonn D, Holden BA, Wong R. Factors affecting rigid gas permeable vertical lens decentration. Optom Vis Sci 1992;69,12s:153.
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..
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.
Fonn D, Sorbara L, Gautheir C. Permeability of rigid lenses: the higher the better?. European Research Symposium Edinburgh, 1989. [ Show Abstract ]
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.
Srinivasan S, Menzies K, Sorbara L, Jones L. Meibography of the upper lid. Optician 2011;242,6318:12-15.
Srinivasan S, Sorbara L, Jones L, Sickenberger W. Imaging the structure of the meibomian glands . Contact Lens Spectrum 2011;26,7:52-53.
Bitton E, Sorbara L. Canadians are alive and well at the AAO in Anaheim 2008. Canadian J Optom 2009;70,1:.
Sorbara L. Report on the Global Specialty Lens Symposium. Contact Lens Spectrum 2009,March:.
Peterson R, Sorbara L. Contact Lenses IV: Lens fit. Optometry Today 2008;48,8:66.
Sorbara L. Contacts by Design. Optical Prism 2005,March:15-20.
Sorbara L. Kids and contacts: when to start . Visual Eyes 2000;3,2:23-26.
Sorbara L, Luong J. Contact lens fitting guidelines for the keratoconic patient using videokeratographic data. Practical Optometry 1999;10,6:238-243.
Higazy MT, Fonn D, Sorbara L. Rigid gas permeable contact lens fitting in keratoconus. Bull Ophthalmol Soc Egypt 1998;91,6:985-988.
Potvin RJ, Fonn D, Sorbara L. In vivo comparison of corneal topography and keratometry systems. Int Contact Lens Clin 1996;23,1:20-26.
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.
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.
Sorbara L. Testing for the contact lens dry-eye patient, expert opinion. Contact Lens Forum 1990;15,2:9.
Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 43. 2017.
Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 42. 2016.
Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 41. 2015.
Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 40. 2014.
Jones L, Sorbara L, Stahl U, Guthrie S, Menzies K, Rossy J, Thom M. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 39. 2013.
Sorbara L, Fonn D, Woods C, Sivak A, Boshart B. Correction of Keratoconus with GP Contact Lenses. Bausch and Lomb. 2010.
Williams L, Sorbara L. Care and Maintenance of GP lenses. In: The IACLE Contact Lens Course, ed. Fonn D. IACLE. 2009.
Bennet ES, Sorbara L. Lens Design, Fitting and Evaluation. In: Clinical Manual of Contact Lenses 3rd Edition, ed. Bennet ES, Henry VA. Lippincott Williams and Wilkens. 2008.
Sorbara L, Fonn D, Woods C, Sivak A, Boshart B. Correction of Presbyopia with GP Contact Lenses. Bausch and Lomb. 2007.
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.
Bennett ES, Sorbara L. Lens Design, Fitting and Evaluation. In: Clinical Manual of Contact Lenses Second Edition, ed. Bennett ES, Henry VA. Lippincott Williams and Wilkens. 2000.