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Michael J Doughty - One of the best experts on this subject based on the ideXlab platform.
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further analysis of the predictability of corneal endothelial cell density estimates when Polymegethism is present
Cornea, 2017Co-Authors: Michael J DoughtyAbstract:Purpose To assess variability in endothelial cell density (ECD) estimates when Polymegethism (variance in cell areas) is present. Methods Using noncontact specular microscope images of the corneal endothelium, 4 sets of 20 cases were selected, which included 200 cells and had coefficient of variation values of less than 30% (group 1), 31%-40% (group 2), 41%-50% (group 3), and over 50% (group 4). A stepwise analysis was undertaken, 20 cells at a time, of the ECD estimates when using different numbers of cells for the calculations. Results The net differences in ECD estimates when comparing sets of 20 cells with 200 cells were 5.0% ± 3.9%, 8.1% ± 7.3%, 11.3% ± 9.4%, and 14.5% ± 12.4% for groups 1 to 4, respectively. For measures on 100 cells per image, the predicted variances in ECD values were 5.6%, 8.8%, 11.1%, and 13.7% for the 4 groups. Conclusions Higher values of corneal endothelial Polymegethism result in predictable increases in the variability (uncertainty) in ECD estimates, thus reducing the "accuracy" of ECD values. There is no obvious utility in assessing more than 100 cells in such endothelia.
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an observational cross sectional study on the corneal endothelium of medium term rigid gas permeable contact lens wearers
Contact Lens and Anterior Eye, 2017Co-Authors: Michael J DoughtyAbstract:Abstract Purpose To assess if Polymegethism and pleomorphism were evident in corneal endothelium after medium-term rigid gas permeable (RGP) contact lens wear. Methods In a cross-sectional observational study over 12 years, single images of the central region of the corneal endothelium of one eye of 46 subjects were taken with a non-contact specular microscope, along with a measure of central corneal thickness (CCT). The images were printed onto A3-sized paper and 100 cells/image measured by planimetry. Results Subjects aged between 20 and 32 years, with an average cumulative RGP wear of 6.0 +/− 1.6 years (range 3–9 years) were assessed; 26 of the subjects were Caucasian and 20 were Asian. The mean CCT was 0.515 +/− 0.027 mm. The group cell area value was 401 +/− 42 sq micron to give an estimated endothelial cell density (ECD) of 2520 +/− 273 cells/sq mm. As compared to a historical database, most endothelia (37/46) showed some changes with the mean coefficient of variation on cell area (COV) being 36.7 +/− 8.0% and the percentage of 6-sided (HEX) being 51.8 +/− 8.8%. There were modest correlations between years of RGP wear and both COV (p = 0.009, r spearman = 0.424) and HEX (p = 0.025, r spearman = −0.291), but not for ECD or CCT. Conclusions Corneal endothelial Polymegethism appears to be a commonplace consequence of RGP lens wear with the magnitude of the change being related to the cumulative duration of the lens wear.
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a prospective analysis of corneal endothelial Polymegethism and cell density in young adult asians
Clinical and Experimental Optometry, 2014Co-Authors: Michael J DoughtyAbstract:The aim was to assess the morphology of the Asian corneal endothelium, particularly the index of Polymegethism and its relationship to endothelial cell density assessments.The central regions of th...
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evaluation of possible error sources in corneal endothelial morphometry with a semiautomated noncontact specular microscope
Cornea, 2013Co-Authors: Michael J DoughtyAbstract:PURPOSE To assess the corneal endothelium, particularly the Polymegethism feature, using the Topcon SP-3000P specular microscope with newer center-dot software. METHODS Forty-eight healthy, normal weight, noncontact lens wearers of Asian ethnicity were assessed. Single endothelial images from each subject were processed with center-dot software, reevaluated after correction of obvious errors, and then by manual border marking and planimetry. Endothelial cell density based on average cell area and the coefficient of variation (COV) of cell area (Polymegethism) were calculated. RESULTS Error sources are associated with erroneous location of cell borders (usually creating larger or smaller "cells") or failure to assign cell borders to a marked cell. On the initial application of the center-dot software, the endothelial cell density values ranged from 1822 to 3244 cells per square millimeter (mean, 2644 cells/mm); this range was reduced (eg, 1955-3054 cells/mm; mean 2690 cells/mm on editing or in manual planimetry). The COV values ranged from 17% to 39% (mean, 27.5% ± 5.5%), with one third of the endothelia yielding COV values of greater than or equal to 30%. On editing or in manual planimetry, the COV values were reduced to between 17% and 29% (mean, 24.5% ± 3.2%; P < 0.001). CONCLUSIONS In the use of a center-dot endothelial analysis program with cell border identification, it is likely that at least 1 set of editing steps is required to produce reasonable results.
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a comparison of two methods for estimating Polymegethism in cell areas of the human corneal endothelium
Ophthalmic and Physiological Optics, 2008Co-Authors: Michael J Doughty, Emil OblakAbstract:Purpose: To compare the outcome measures from two different methods for estimating the coefficient of variation (COV) in cell area for human corneal endothelia. Methods: A single non-contact specular micrograph was obtained from the central region of the corneal endothelium of 100 healthy non-contact lens-wearing white European subjects, aged from 32 to 62 years. The captured image file was either assessed using a machine-based algorithm in which 21 cells were marked and their areas reported (designated as the TOPCON ‘centre-dot’ method), or by an overlay and semi-automated computer-based image analysis system of the entire image of around 200 cells (designated as the AUTO method). The average cell area values were used to calculate the endothelial cell density (ECD), while the COV was calculated from the standard deviation of the cell area measures. Results: The TOPCON and AUTO methods yielded comparable data for average cell area (395 vs 391 μm2) and estimated ECD (2566 vs 2575 cells mm−2) that were not statistically different (p ≥ 0.351), although there was a slight bias between the two methods. However, the mean COV values were very different at 43.5 and 31.4% (p < 0.001). The overestimation of the COV was related to the difference in the largest cell area domain identified by the two methods (p < 0.001, r = ≥0.748). Conclusions: A centre-dot method using a small number of cells generates useful data on cell area and ECD, but it should be used cautiously for estimates of COV.
Gavet Yann - One of the best experts on this subject based on the ideXlab platform.
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Perception visuelle humaine, complétion des mosaïques et application à la reconstruction d'images de l'endothélium cornéen humain en microscopie optique spéculaire
2008Co-Authors: Gavet Yann, Pinoli Jean-charlesAbstract:L'endothélium cornéen humain constitue une mono-couche de cellules de formes relativement hexagonales et de surfaces régulières, situées à la face interne de la cornée. Ces cellules sont primordiales car elles maintiennent la transparence de la cornée. Leurs contours sont facilement photographiés chez le patient grâce à la microscopie optique spéculaire (in vivo), ou sur un greffon (ex vivo) grâce à la microscopie optique classique. Les ophtalmologistes s'intéressent alors à la densité cellulaire, ainsi qu'à des caractéristiques morphométriques (polymégethisme et pléomorphisme). Leur analyse, lorsqu'elle utilise des logiciels spécifiques, n'est cependant jamais aussi pertinente que l'analyse visuelle. Ce constat nous a conduit à nous intéresser aux principes qui régissent la perception visuelle humaine. Dans cette thèse, nous vérifions de manière élémentaire que les principes de bonne continuation et de proximité de la théorie de la Gestalt sont vérifiés algorithmiquement sur des cas simples, ce qui permet d'envisager leur utilisation pour fermer les contours imparfaitement détectés dans les images. Cependant, les résultats obtenus suggèrent une intéraction complexe entre ces principes. L'utilisation de méthodes morphologiques basées sur des filtres alternés séquentiels, des cartes de distances et des lignes de partage des eaux fournit de bons résultats. Il est montré que ces méthodes sont fondées sur les principes de la théorie de la Gestalt: la proximité est introduite par les cartes de distances, la continuation et la fermeture sont des propriétés des lignes de partage des eaux. Leur utilisation conjointe permet de réaliser une analyse duale contours-régions: les cartes de distances permettent d'accéder à des informations régionales à partir des contours, alors que les lignes de partage des eaux permettent d'obtenir des informations de contours à partir de marqueurs régionaux. Ces impressions ont été vérifiées en mettant en place un critère de dissimilarité qui permet de quantifier l'erreur entre une mosaïque (structure cellulaire observée sur l'image de l'endothélium) fournie par l'expert et une autre mosaïque. Ainsi, plusieurs méthodes de segmentation sont testées, et la méthode que nous proposons donne les meilleurs résultats. Ce critère de dissimilarité a permis de trouver les meilleurs paramètres de chaque méthode et de faire établir entre elles un classement par les ophtalmologistes. Pour terminer la segmentation des images, une validation des résultats, basée sur des paramètres de formes, est proposée.Human corneal endothelium constitutes a monolayer of relatively hexagonal cells with irregular surfaces situated on the internal side of the cornea. These cells are fundamental because they preserve the transparency of the cornea. Their contours can be easily photographed on a patient, using optical specular microscopy (in vivo), or on a graft (ex vivo), using classic optical microscopy. Ophtalmologists then take an interest in cell density as well as in morphometric characteristcs (polymegathism and pleomorphism). However, their analysis using specific sofware is never as relevant as visual analysis. This observation led us to focus on the principles which govern human visual perception. In this thesis we verify in an elementary way that the principles of good continuation and proximity of the Gestalt theory are algorithmically verified on simple cases. This allows us to consider their use to close the contours that are imperfectly detected on images. Nevertheless, the results that are obtained suggest a complex interaction between those principles. The use of morphological methods based on sequential alternate filters, distance maps and watersheds provide good results. It is shown that these methods are based on the principles of Gestalt theory: proximity is introduced by the distance maps, continuation and closing are properties of the watershed operator. Their combined use allows the realization of a dual analysis contours-régions'': distance maps give access to regional information based on the contours, whereas watersheds provide contour information based on regional markers. These impressions were verified by setting up a dissimilarity criterion which allows us to quantify the differences between a mosaic (cell structure observed on the picture of the endothelium) provided by an expert and another mosaic. Thus, several segmentation methods are tested, and the method we put forward gives the best results. This criterion of dissimilarity allowed us to find the best parameters of each method and to have a ranking established among them by ophtalmologists. In order to complete the segmentation of the images, we put forward a validation based on shape parameters.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF
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Perception visuelle humaine, complétion des mosaïques et application à la reconstruction d'images de l'endothélium cornéen humain\\ en microscopie optique spéculaire
HAL CCSD, 2008Co-Authors: Gavet YannAbstract:218 pagesHuman corneal endothelium constitutes a monolayer of relatively hexagonal cells with irregular surfaces situated on the internal side of the cornea. These cells are fundamental because they preserve the transparency of the cornea. Their contours can be easily photographed on a patient, using optical specular microscopy (in vivo), or on a graft (ex vivo), using classic optical microscopy. Ophtalmologists then take an interest in cell density as well as in morphometric characteristcs (polymegathism and pleomorphism). However, their analysis using specific sofware is never as relevant as visual analysis. This observation led us to focus on the principles which govern human visual perception. In this thesis we verify in an elementary way that the principles of good continuation and proximity of the Gestalt theory are algorithmically verified on simple cases. This allows us to consider their use to close the contours that are imperfectly detected on images. Nevertheless, the results that are obtained suggest a complex interaction between those principles. The use of morphological methods based on sequential alternate filters, distance maps and watersheds provide good results. It is shown that these methods are based on the principles of Gestalt theory: proximity is introduced by the distance maps, continuation and closing are properties of the watershed operator. Their combined use allows the realization of a dual analysis "contours-régions'': distance maps give access to regional information based on the contours, whereas watersheds provide contour information based on regional markers. These impressions were verified by setting up a dissimilarity criterion which allows us to quantify the differences between a mosaic (cell structure observed on the picture of the endothelium) provided by an expert and another mosaic. Thus, several segmentation methods are tested, and the method we put forward gives the best results. This criterion of dissimilarity allowed us to find the best parameters of each method and to have a ranking established among them by ophtalmologists. In order to complete the segmentation of the images, we put forward a validation based on shape parametersL'endothélium cornéen humain constitue une mono-couche de cellules de formes relativement hexagonales et de surfaces régulières, situées à la face interne de la cornée. Ces cellules sont primordiales car elles maintiennent la transparence de la cornée. Leurs contours sont facilement photographiés chez le patient grâce à la microscopie optique spéculaire (in vivo), ou sur un greffon (ex vivo) grâce à la microscopie optique classique. Les ophtalmologistes s'intéressent alors à la densité cellulaire, ainsi qu'à des caractéristiques morphométriques (polymégethisme et pléomorphisme). Leur analyse, lorsqu'elle utilise des logiciels spécifiques, n'est cependant jamais aussi pertinente que l'analyse visuelle. Ce constat nous a conduit à nous intéresser aux principes qui régissent la perception visuelle humaine. Dans cette thèse, nous vérifions de manière élémentaire que les principes de bonne continuation et de proximité de la théorie de la Gestalt sont vérifiés algorithmiquement sur des cas simples, ce qui permet d'envisager leur utilisation pour fermer les contours imparfaitement détectés dans les images. Cependant, les résultats obtenus suggèrent une intéraction complexe entre ces principes. L'utilisation de méthodes morphologiques basées sur des filtres alternés séquentiels, des cartes de distances et des lignes de partage des eaux fournit de bons résultats. Il est montré que ces méthodes sont fondées sur les principes de la théorie de la Gestalt: la "proximité'' est introduite par les cartes de distances, la "continuation'' et la "fermeture'' sont des propriétés des lignes de partage des eaux. Leur utilisation conjointe permet de réaliser une analyse duale contours-régions: les cartes de distances permettent d'accéder à des informations régionales à partir des contours, alors que les lignes de partage des eaux permettent d'obtenir des informations de contours à partir de marqueurs régionaux. Ces impressions ont été vérifiées en mettant en place un critère de dissimilarité qui permet de quantifier l'erreur entre une mosaïque (structure cellulaire observée sur l'image de l'endothélium) fournie par l'expert et une autre mosaïque. Ainsi, plusieurs méthodes de segmentation sont testées, et la méthode que nous proposons donne les meilleurs résultats. Ce critère de dissimilarité a permis de trouver les meilleurs paramètres de chaque méthode et de faire établir entre elles un classement par les ophtalmologistes. Pour terminer la segmentation des images, une validation des résultats, basée sur des paramètres de formes, est proposée
Sara M. Thomasy - One of the best experts on this subject based on the ideXlab platform.
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biomechanical changes to descemet s membrane precede endothelial cell loss in an early onset murine model of fuchs endothelial corneal dystrophy
Experimental Eye Research, 2019Co-Authors: Brian C Leonard, Vijay Krishna Raghunathan, Christopher J Murphy, Iman Jalilian, Wei Wang, Sara M. ThomasyAbstract:Abstract Early-onset Fuchs endothelial corneal dystrophy (FECD) has been associated with nonsynonymous mutations in collagen VIII α2 (COL8A2), a key extracellular matrix (ECM) protein in Descemet's membrane (DM). Two knock-in strains of mice have been generated to each express a mutant COL8A2 protein (Col8a2L450W/L450W and Col8a2Q455K/Q455K) that recapitulate the clinical phenotype of early-onset FECD including endothelial cell loss, cellular polymegathism and pleomorphism, and guttae. Due to abnormalities in ECM protein composition and structure in FECD, the stiffness of DM in Col8a2 knock-in mice and wildtype (WT) controls was measured using atomic force microscopy at 5 and 10 months of age, coinciding with the onset of FECD phenotypic abnormalities. At 5 months, only sporadic guttae were identified via in vivo confocal microscopy (IVCM) in Col8a2Q455K/Q455K mice, otherwise both strains of Col8a2 transgenic mice were indistinguishable from WT controls in terms of endothelial cell density and size. By 10 months of age, Col8a2L450W/L450W and Col8a2Q455K/Q455K mice developed reduced corneal endothelial density, increased endothelial cell area and guttae, with the Col8a2Q455K/Q455K strain exhibiting a more severe phenotype. However, at 5 months of age, prior to the development endothelial cell abnormalities, Col8a2L450W/L450W and Col8a2Q455K/Q455K mice knock-in mice had reduced tissue stiffness of DM that was statistically significant in the Col8a2Q455K/Q455K mice when compared with wildtype controls. These data indicate that alterations in the tissue compliance of DM precede phenotypic changes in endothelial cell count and morphology, and may play a role in onset and progression of FECD.
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in vivo imaging of corneal endothelial dystrophy in boston terriers a spontaneous canine model for fuchs endothelial corneal dystrophy
Investigative Ophthalmology & Visual Science, 2016Co-Authors: Sara M. Thomasy, Dennis E Cortes, Alyssa L Hoehn, Allison C Calderon, Jennifer Y Li, Christopher J MurphyAbstract:PURPOSE: Boston Terriers (BTs) have a greater prevalence of corneal endothelial dystrophy (CED), in comparison to other canine breeds. Similar to Fuchs' endothelial corneal dystrophy (FECD), this condition is characterized by endothelial cell degeneration with secondary corneal edema. This study assessed corneal morphology using in vivo confocal microscopy (IVCM) and Fourier-domain optical coherence tomography (FD-OCT) in BTs with and without CED. METHODS: The corneas of 16 BTs with CED and 15 unaffected, age-matched BTs underwent clinical evaluation and were imaged using IVCM and FD-OCT. A two-sample t-test or Mann-Whitney rank sum test were used to statistically compare parameters between groups. Data are presented as mean ± SD or median (range). RESULTS: Mean age did not significantly differ between affected and unaffected dogs at 10.0 ± 2.0 and 10.6 ± 2.4 years, respectively (P = 0.437). Females (69%) were overrepresented among the CED-affected dogs. In CED patients, IVCM demonstrated endothelial polymegathism and pleomorphism. Corneal endothelial density was significantly less (P < 0.001) in dogs with CED (1026 ± 260 cells/mm2) versus age-matched controls (2297 ± 372 cells/mm2). Fourier-domain OCT demonstrated a significant increase (P < 0.01) in central corneal and endothelium-Descemet's complex thickness in dogs with CED versus age-matched controls at 1019 (485-1550) or 536 (464-650) μm and 32 (22-56) or 25 (15-34) μm, respectively. CONCLUSIONS: Corneal endothelial dystrophy in BTs is a bilateral, adult-onset condition that shares many similarities with FECD. Thus, CED could serve as a spontaneous disease model to study the pathogenesis of and develop novel treatments for FECD.
Christopher J Murphy - One of the best experts on this subject based on the ideXlab platform.
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biomechanical changes to descemet s membrane precede endothelial cell loss in an early onset murine model of fuchs endothelial corneal dystrophy
Experimental Eye Research, 2019Co-Authors: Brian C Leonard, Vijay Krishna Raghunathan, Christopher J Murphy, Iman Jalilian, Wei Wang, Sara M. ThomasyAbstract:Abstract Early-onset Fuchs endothelial corneal dystrophy (FECD) has been associated with nonsynonymous mutations in collagen VIII α2 (COL8A2), a key extracellular matrix (ECM) protein in Descemet's membrane (DM). Two knock-in strains of mice have been generated to each express a mutant COL8A2 protein (Col8a2L450W/L450W and Col8a2Q455K/Q455K) that recapitulate the clinical phenotype of early-onset FECD including endothelial cell loss, cellular polymegathism and pleomorphism, and guttae. Due to abnormalities in ECM protein composition and structure in FECD, the stiffness of DM in Col8a2 knock-in mice and wildtype (WT) controls was measured using atomic force microscopy at 5 and 10 months of age, coinciding with the onset of FECD phenotypic abnormalities. At 5 months, only sporadic guttae were identified via in vivo confocal microscopy (IVCM) in Col8a2Q455K/Q455K mice, otherwise both strains of Col8a2 transgenic mice were indistinguishable from WT controls in terms of endothelial cell density and size. By 10 months of age, Col8a2L450W/L450W and Col8a2Q455K/Q455K mice developed reduced corneal endothelial density, increased endothelial cell area and guttae, with the Col8a2Q455K/Q455K strain exhibiting a more severe phenotype. However, at 5 months of age, prior to the development endothelial cell abnormalities, Col8a2L450W/L450W and Col8a2Q455K/Q455K mice knock-in mice had reduced tissue stiffness of DM that was statistically significant in the Col8a2Q455K/Q455K mice when compared with wildtype controls. These data indicate that alterations in the tissue compliance of DM precede phenotypic changes in endothelial cell count and morphology, and may play a role in onset and progression of FECD.
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in vivo imaging of corneal endothelial dystrophy in boston terriers a spontaneous canine model for fuchs endothelial corneal dystrophy
Investigative Ophthalmology & Visual Science, 2016Co-Authors: Sara M. Thomasy, Dennis E Cortes, Alyssa L Hoehn, Allison C Calderon, Jennifer Y Li, Christopher J MurphyAbstract:PURPOSE: Boston Terriers (BTs) have a greater prevalence of corneal endothelial dystrophy (CED), in comparison to other canine breeds. Similar to Fuchs' endothelial corneal dystrophy (FECD), this condition is characterized by endothelial cell degeneration with secondary corneal edema. This study assessed corneal morphology using in vivo confocal microscopy (IVCM) and Fourier-domain optical coherence tomography (FD-OCT) in BTs with and without CED. METHODS: The corneas of 16 BTs with CED and 15 unaffected, age-matched BTs underwent clinical evaluation and were imaged using IVCM and FD-OCT. A two-sample t-test or Mann-Whitney rank sum test were used to statistically compare parameters between groups. Data are presented as mean ± SD or median (range). RESULTS: Mean age did not significantly differ between affected and unaffected dogs at 10.0 ± 2.0 and 10.6 ± 2.4 years, respectively (P = 0.437). Females (69%) were overrepresented among the CED-affected dogs. In CED patients, IVCM demonstrated endothelial polymegathism and pleomorphism. Corneal endothelial density was significantly less (P < 0.001) in dogs with CED (1026 ± 260 cells/mm2) versus age-matched controls (2297 ± 372 cells/mm2). Fourier-domain OCT demonstrated a significant increase (P < 0.01) in central corneal and endothelium-Descemet's complex thickness in dogs with CED versus age-matched controls at 1019 (485-1550) or 536 (464-650) μm and 32 (22-56) or 25 (15-34) μm, respectively. CONCLUSIONS: Corneal endothelial dystrophy in BTs is a bilateral, adult-onset condition that shares many similarities with FECD. Thus, CED could serve as a spontaneous disease model to study the pathogenesis of and develop novel treatments for FECD.
Gregory Kracher - One of the best experts on this subject based on the ideXlab platform.
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specular microscopy studies on the corneal endothelium after cessation of contact lens wear
Cornea, 1991Co-Authors: Maria Elena Sibug, Manuel B Datiles, K Kashima, Lessie Mccain, Gregory KracherAbstract:: We performed specular microscopy on the corneal endothelium of 22 long-term hard contact lens wearers (15-32 years duration) and 22 age- and sex-matched controls. We found Polymegethism in users as shown by a significant difference in the coefficient of variation in cell area (p less than 0.01) and pleomorphism as shown by a significant decrease in the percent of 6-sided cells (hexagonality, p less than 0.01). There was no significant difference in cell density and mean cell area between the 2 groups. Contact lens wear was discontinued in five eyes of three patients after they were entered into the study and switched to eye-glasses. Specular micrographs were taken up to 60 months after discontinuation of use of the lenses. Comparison of the above parameters before and after discontinuation of the lenses did not show a significant change. However, there was a trend toward improvement in the coefficient of variation in the eyes that were followed the longest. This finding suggests that the morphological changes induced by long-term use of contact lenses may be slowly reversible after prolonged discontinuation of contact lens wear.