Peer-reviewed Articles

Please use the archived list on the right to look at past peer-reviewed articles.

2007

Bitton,E., Keech,A., Simpson,T., Jones,L. Variability of the analysis of the tear meniscus height by optical coherence tomography. Optometry and Vision Science 2007;84,9:E903-E908. [ Show Abstract ]

PURPOSE. Tear meniscus height (TMH) is an established parameter indicative of tear film volume and has recently been determined using an optical coherence tomographer (OCT). The purpose of this study was to evaluate the inter and intra observer variability in TMH assessment using OCT. METHODS. Ten subjects (6 M, 4 F; aged 32.5 ± 6.4 years) had 10 consecutive scans taken of their inferior central tear meniscus (5 scans originating at 90° and 5 origination at 270°) using the OCT2 (Humphrey-Zeiss). Images were analyzed by two observers using custom software on three separate occasions. Following a training session among observers, the images were reevaluated to assess differences in variability. Data were analyzed for differences within and across examiners, for the effect of examiner training and between scan directions. RESULTS. The mean TMH and tear volume collapsed across subjects were between 0.24 and 0.25 mm and 25 to 27 nL/mm, respectively. No difference was noted within observers. An interobserver mean volume difference (p = 0.044) was present but was eliminated post training (p = 0.167). Variability was less with scans originating at 90°. CONCLUSIONS. The values of the TMH and tear volume are similar to those reported in the literature. Due to the interobserver differences observed, a training session between examiners may prove to be valuable, especially in a large or multicenter study. © 2007 American Academy of Optometry.

Dracopoulos,A., Dixon,D. G., Jones,L. W., Sivak,J. G., Bantseev,V. In vitro assessment of medical device toxicity: Interactions of benzalkonium chloride with silicone-containing and p-HEMA-containing hydrogel contact lens materials. Eye and Contact Lens 2007;33,1:26-37. [ Show Abstract ]

PURPOSE. To analyze the interactions of benzalkonium chloride (BAK) with silicone-containing (lotrafilcon A and galyfilcon A) and p-HEMA-containing (etafilcon A and vifilcon A) hydrogel contact lenses and to examine the possibility of using sodium fluorescein permeability assay (SFPA), 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the bovine lens assay in conjunction with confocal laser scanning microscopy (CLSM) as a battery of in vitro alternatives to evaluate the potential toxicity of soft contact lenses. METHODS. Four soft contact lens types (Focus Monthly [vifilcon A], Focus NIGHT & DAY [lotrafilcon A], ACUVUE Advance With Hydraclear [galyfilcon A], and SUREVUE [etafilcon A]) were soaked for 24 hours in various concentrations of BAK (1%, 0.1%, 0.01%, and 0.001%) in 20-mL glass vials. After 24 hours, the lenses were gently washed in Hanks' Balanced Salt Solution (HBSS), placed in 5 mL of HBSS, and incubated for a total of 7 days at 37°C, 5% CO2. BAK released into HBSS (i.e., the extract) was recovered from the vials and used as the test chemical in the SFPA (epithelium integrity), MTT assay (cellular viability), and the bovine lens assay with CLSM (mitochondrial metabolism and optical properties). The amount of BAK extracted from the various contact lenses was measured using an Abbe refractometer. Negative controls consisted of HBSS and contact lenses subjected to the same conditions as the treated contact lenses, but without BAK. RESULTS. Extracts obtained from soaking Focus Monthly lenses in BAK caused the most damage to the epithelium and mitochondrial metabolism. However, at 0.1% BAK extraction, all lens extracts showed increased levels of back vertex distance variability of the cultured bovine lens. CONCLUSIONS. Unexpectedly, lenses extracted with HBSS showed SFPA and MTT assay responses and an observed effect on the bovine lens epithelium visualized by CLSM, indicating that unknown chemical agents may be leached from contact lens polymers. © 2007 Lippincott Williams & Wilkins, Inc.

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.

Klenkler,B., Sheardown,H., Jones,L. Growth factors in the tear film: Role in tissue maintenance, wound healing, and ocular pathology. Ocular Surface 2007;5,3:228-239. [ Show Abstract ]

Numerous biologically active growth factors are secreted by the lacrimal gland and distributed via the tears over the ocular surface where they affect cellular proliferation, migration, differentiation, and survival. The role of growth factors and their receptors in maintenance of tissue homeostasis and wound healing continues to be elucidated, and the effect of growth factor imbalances In ocular surface diseases is just beginning to be understood. For Instance, in eyes with ocular surface diseases, Including conjunctivitis, corneal erosion, keratitis, and corneal ulcers, epidermal growth factor release rates have been shown to be significantly lower than in normal eyes during reflex tearing. Future research into the mechanisms of dry eye disease will focus on reasons for decreased tear and growth factor production in the neuronal reflex loop or the acinar lacrimal gland cells. Animal models to test therapeutic approaches must be developed. © 2007 Ethis Communications, Inc.

Lorentz,H., Jones,L. Lipid deposition on hydrogel contact lenses: How history can help us today. Optometry and Vision Science 2007;84,4:286-295. [ Show Abstract ]

The tear film is a complex fluid that is precisely maintained and which is essential to the health of the ocular surface. One of the major components of the tear film is lipid, which is produced by the meibomian glands and serves many important functions on the ocular surface. It is estimated that there are more than 45 individual lipids within the tear film, which vary greatly in their structure and properties. The composition of the lipid within the tear film has an enormous influence on the stability of the tear film, with a subsequent impact on the occurrence of dry eye and the ultimate success of contact lens wear. The purpose of this review article is to describe the composition of the tear film lipids and their interaction with contact lens materials, with a particular emphasis on how the chemistry of novel silicone hydrogel materials has resulted in clinicians needing to understand the deposition of lipids onto contact lenses and how they may best manage this complication.

Lorentz,H., Rogers,R., Jones,L. The impact of lipid on contact angle wettability. Optometry and Vision Science 2007;84,10:946-953.

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.

Luensmann,D., Glasier,M. -A, Zhang,F., Bantseev,V., Simpson,T., Jones,L. Confocal microscopy and albumin penetration into contact lenses. Optometry and Vision Science 2007;84,9:839-847. [ Show Abstract ]


Purpose. To develop a novel in vitro method to detect the depth of penetration of the tear film protein albumin into contact lens materials using confocal laser scanning microscopy (CLSM).
Methods. A poly-HEMA-based hydrogel (etafilcon A) and a silicone hydrogel material (lotrafilcon B) were examined. In vitro, bovine serum albumin (BSA) was labeled with 5-(4,6-dichloro-s-triazin-2-ylamino) fluorescein hydrochloride (DTAF). The lenses were incubated in this protein solution (0.5 mg/ml) at 37°C. After 1 and 7 days incubation, the lenses were examined using CLSM (Zeiss 510, config. META 18) and the location of the fluorescently labeled BSA was identified.
Results. BSA adsorption on the surface and penetration into the lens matrix occurred at a higher concentration for etafilcon compared to lotrafilcon (p < 0.001). For both materials, BSA was detected on the surface after 1 day of incubation. Significant levels of BSA were detected within the matrix of etafilcon after as little as 1 day (p < 0.001), but no BSA was detected in the matrix of lotrafilcon at any time (p > 0.05).
Conclusion. CLSM can be successfully used to examine the depth of penetration of fluorescently labeled proteins into various hydrogel polymers. Our results show that etafilcon lenses both adsorb BSA on the surface and absorb BSA within the matrix, whereas lotrafilcon B adsorbs small amounts of BSA on the surface only.

Schulze,M. M., Jones,D. A., Simpson,T. L. The development of validated bulbar redness grading scales. Optometry and Vision Science 2007;84,10:976-983. [ Show Abstract ]

PURPOSE: To develop a perceptually and physically based bulbar redness grading scale. METHODS: Digital conjunctival hyperemia photographs were taken using a photo-slit lamp at controlled exposures. Nine participants arranged 25 images on a tabletop over a range of 1.5 m, using separation to represent changes in redness. The position of each image was recorded and normalized for a 0 to 100 scale, and compared to chromaticity of each image obtained using a spectrophotometer. The performance of two versions of the scale (5 and 10 images) and a continuous grading scale was evaluated based on repeatability data collected from nineteen observers who used each scale twice to grade 30 randomly presented images of bulbar redness. RESULTS: Psychophysical scaling was highly correlated between single observers (Pearson's r >or= 0.92, p < 0.05). The averaged subjective grades significantly correlated with chromaticity (r = 0.95 and r = 0.99, p < 0.001 for CIE u* and log u*, respectively). Across all observers, test and retest ratings were highly correlated with either scale (r >or= 0.98), and showed high levels of repeatability expressed by intraclass correlation coefficients (ICC >or= 0.98), correlation coefficients of concordance (CCC >or= 0.96), and coefficients of repeatability (COR <or= 5.64). Despite single unit increment options, the majority of grade values assigned using the discrete scales were distributed in multiples of 5. CONCLUSIONS: Combining psychophysical and physical attributes is a promising method for the development of novel anterior segment scales; the newly developed scales performed well in a clinical setting.

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.

Srinivasan,S., Chan,C., Jones,L. Apparent time-dependent differences in inferior tear meniscus height in human subjects with mild dry eye symptoms. Clinical and Experimental Optometry 2007;90,5:345-350. [ Show Abstract ]

PURPOSE: The aim of the study was to track the volume of tears contained in the inferior tear meniscus over the course of the day in subjects with symptoms of mild dry eye and a control asymptomatic group. METHODS: Forty non-contact lens-wearing subjects (aged 27 +/- 6 years) were enrolled in this investigator-masked study. They were divided into 'dry eye' (DE) and 'non-dry eye' (NDE) individuals based on their responses to the Allergan Subjective Evaluation of Symptoms of Dryness (SESOD) questionnaire. Measurement of the tear meniscus height (TMH) was undertaken on the centre of the right eye at 9:00 am, noon, 3:00 pm, 6:00 pm and 9:00 pm on the lower lid using a non-contact, non-invasive optical coherence tomographer (OCT). The TMH was determined from scanned images using customised software. RESULTS: A monotonous and significant reduction in the central TMH occurred over the course of the day in both groups (p < 0.05), with the values constantly decreasing (NDE = 0.162 to 0.125 mm; DE = 0.154 to 0.121 mm). While the TMH values in the DE group were always lower than the NDE group, these were not significantly different at any time (p > 0.05). CONCLUSIONS: A diurnal reduction in tear volume, as assessed by evaluation of the inferior TMH, may be one of the reasons responsible for the common increase in end-of-day ocular dryness symptoms reported by many patients in clinical practice.

Srinivasan,S., Joyce,E., Jones,L. W. Tear osmolality and ferning patterns in postmenopausal women. Optometry and Vision Science 2007;84,7:588-592. [ Show Abstract ]

PURPOSE: To compare tear osmolality and ferning patterns in postmenopausal women (PMW) with and without dry eye symptoms. METHODS: Thirty-seven healthy PMW (>50 years of age), not on hormone replacement therapy, were categorized as being symptomatic or asymptomatic of dry eye based on their responses to an Allergan "Single-Item Score Dry Eye Questionnaire" (SIDEQ). They subsequently completed the Allergan "Ocular Surface Disease Index" (OSDI) questionnaire. Tear samples were collected from participants to evaluate osmolality and ferning patterns. A novel freezing point depression osmometer (Advanced Instruments Inc., Model 3100 Tear Osmometer), was used to measure the osmolality of the tear film. The tear ferning test was performed and evaluated for the quality of ferning based on the Rolando grading system. RESULTS: SIDEQ responses revealed 21 symptomatic and 16 asymptomatic participants. The OSDI total score was 6.5 +/- 5.9 for the non-dry-eyed (NDE) group and 25.7 +/- 12.4 for the dry-eyed (DE) group. The subscores for the DE group were significantly greater than the NDE group (p < 0.001). Osmolality values in DE individuals were significantly different from NDE (328.1 +/- 20.8 vs. 315.1 +/- 11.3 mOsm/kg; p = 0.02). Fifty percent of the DE participants showed type II ferning patterns and 29% of the DE participants showed type III ferning patterns, whereas the NDE participants showed either type I (44%) or II (66%) ferning patterns. There was a significant difference between the DE and NDE participants for the ferning patterns (p = 0.019). There was no significant correlation between tear osmolality and tear ferning (DE: r = 0.12; p > 0.05, NDE: r = -0.17; p > 0.05). CONCLUSIONS: Osmolality in mild and moderately DE PMW is higher than in NDE PMW and tear ferning is a rapid, simple, noninvasive laboratory procedure that indicates altered tear quality in PMW with symptoms of dry eye.

Subbaraman,L. N., Glasier,M. A., Senchyna,M., Sheardown,H., Jones,L. Extraction efficiency of an extraction buffer used to quantify lysozyme deposition on conventional and silicone hydrogel contact lens materials. Eye and Contact Lens 2007;33,4:169-173. [ Show Abstract ]

PURPOSE: Extracting lysozyme from Food and Drug Administration group IV etafilcon lenses by using 0.2% trifluoroacetic acid and acetonitrile (TFA/ACN) is a well-established procedure. TFA/ACN has been the extraction buffer of choice for extracting proteins from silicone hydrogel contact lenses. The purpose of this study was to determine the efficiency of TFA/ACN in extracting lysozyme from silicone hydrogel and etafilcon lenses by using an in vitro model. METHODS: ACUVUE 2, Focus NIGHT & DAY, O2 Optix, PureVision, and ACUVUE Advance lenses were incubated in simple lysozyme solution and a complex artificial tear solution consisting of multiple tear components containing lysozyme labeled with iodine 125. All the silicone hydrogel lenses were incubated for 28 days, whereas the ACUVUE 2 lenses were incubated for 7 days at 37 degrees C with constant rotation. After the incubation period, radioactive counts were determined, and the lenses were placed in an appropriate volume of the buffer for 24 hours in darkness. The lenses were removed from the buffer, and radioactive counts were determined again. RESULTS: Extraction efficiencies for lysozyme from the artificial tear solution were 97.2% +/- 1.2% for ACUVUE 2, 64.3% +/- 6.2% for Focus NIGHT & DAY, 62.5% +/- 5.6% for O2 Optix, 53.5% +/- 5.8% for PureVision, and 89.2% +/- 3.4% for ACUVUE Advance. Results were similar for the lysozyme extracted after incubating in the simple lysozyme solution. CONCLUSIONS: TFA/ACN is extremely efficient at extracting lysozyme deposited on etafilcon lenses. However, it does not extract all the lysozyme deposited on silicone hydrogel lenses, and alternative extraction procedures should be sought.

Suwala,M., Glasier,M. -A, Subbaraman,L. N., Jones,L. Quantity and conformation of lysozyme deposited on conventional and silicone hydrogel contact lens materials using an in vitro model. Eye and Contact Lens 2007;33,3:138-143. [ Show Abstract ]

PURPOSE: To determine the activity of hen egg lysozyme (HEL) deposited on conventional and silicone hydrogel contact lens materials by using an in vitro model. METHODS: ACUVUE 2 (etafilcon A), PureVision (balafilcon A), ACUVUE Advance (galyfilcon A), Focus NIGHT & DAY (lotrafilcon A), O2 Optix (lotrafilcon B), Proclear (omafilcon A), and ACUVUE OASYS (senofilcon A) contact lenses were deposited in vitro in a phosphate-buffered solution (PBS) containing 2 mg/mL HEL. Lenses were briefly rinsed in PBS to remove unbound material and extracted in a mixture of acetonitrile and trifluoroacetic acid. After lyophilization, extracts were examined for lysozyme activity by micrococcal assay and total protein by Western blot. RESULTS: In terms of total protein accumulation, ACUVUE 2 showed the most, with 1,800 microg per lens. Proclear was next, with 68 microg per lens, and Focus NIGHT & DAY showed the least, with 2 microg per lens. ACUVUE Advance, ACUVUE OASYS, and O2 Optix accumulated similar amounts of lysozyme, at approximately 6 microg per lens. Lysozyme deposited on ACUVUE 2 showed the greatest activity (91% +/- 5%), and this result was statistically different from all other lens types (P<0.001). Lysozyme deposited on Focus NIGHT & DAY (24% +/- 5%) and O2 Optix (23% +/- 11%) showed the lowest activity. Lysozyme deposits on other lens materials showed intermediate activity (ACUVUE Advance, 60% +/- 15%; ACUVUE OASYS, 51% +/- 9%; PureVision, 58% +/- 8%; and Proclear, 38% +/- 3%). CONCLUSIONS: Silicone hydrogel lenses acquire less lysozyme deposit than conventional group II (Proclear) or group IV (ACUVUE 2) lenses do, and the levels of activity of the lysozyme are highly variable between materials.

Woods,C. A., Jones,D. A., Jones,L. W., Morgan,P. B. A seven year survey of the contact lens prescribing habits of Canadian optometrists. Optometry and Vision Science 2007;84,6:505-510. [ Show Abstract ]

PURPOSE: Little is known about the contact lens prescribing habits of optometrists in North America. The purpose of this survey was to obtain data on the types of lenses and solutions prescribed by Canadian optometrists. METHODS: One thousand Canadian optometrists were surveyed annually over seven consecutive years (2000 to 2006; n = 7000) on their contact lens prescribing preferences. Each survey requested a range of information about the contact lenses prescribed to the first 10 patients after its receipt. RESULTS: Over this time period, 1008 (14.4%) of the surveys were returned, providing data on 9383 fits. During the seven-year period, the ratio of male:female fits was 1:2 (3123:6217, 43 not reported), with a mean age of 31.3 +/- 13.6 years (range 2 to 82 years). The ratio of new fits to refits was 2:3 (3780:5518, 85 not reported), with 91.3% of all fits being soft contact lenses (SCL). Of the SCL fits, 59.5% were spherical, 28.5% toric, 9.7% multifocal, and 2.3% cosmetic tints. Gas permeable (GP) fits were 46.6% spherical, 18.6% toric, 19.5% multifocal, and 6.6% were for orthokeratology (OK). Over the seven-year period, SCL prescribed for continuous wear (CW) increased from 3.2% to 14.3% between 2000 and 2004 and reduced to 8.1% in 2006, for all fits. The use of mid-water content (MWC) materials decreased from 34.6% to 2.7% and the use of silicone hydrogel (SH) lenses increased from 61.4% to 96.2%, for all CW fits. GP lens continuous wear increased from 0.7% to 30.6% of all GP lens fits by 2006. Daily wear (DW) of SH lenses decreased from 49.6% (2000) to 33.7% (2004) and then increased to 86.1% in 2006, for SH fits. MWC SCL fit on a monthly planned replacement (PR) basis reduced in popularity over the seven-year period (75.0% to 39.9%) and in 2006 more patients were fit overall with SH lenses (42.9%). The use of non-PR SCL declined from 20.5% to 4.5% of all fits. Fitting of low-water content lenses also declined (15.1% to 7.0%). High-water content (5.4% to10.2%) and SH lenses (5.4% to 42.9%) both increased. By 2006, the majority of GP lenses fit were with high Dk (HDK) materials (50.3%). CONCLUSIONS: The preferred contact lens modality for Canadian optometrists appears to be DW SCL, which are replaced monthly. The proportion of lenses used for CW peaked in 2004, with SH SCL being the preferred material. The market share for GP lenses remains relatively unchanged, with an increasing proportion used for OK and CW. The launch of DW SH lenses in 2004 resulted in a marked increase in their reported fits, with a similar effect following the launch of a HDK GP lens material for CW.