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Purpose: To visualize in vivo and quantify the thickness of the posterior corneal layers: the acellular pre-Descemet's layer (PDL), Descemet's membrane (DM), and endothelium (END) in healthy subjects, using ultrahigh-resolution optical coherence tomography (UHR-OCT)., Methods: A research-grade, 800-nm UHR-OCT system with 0.95-μm axial resolution in corneal tissue was used to image in vivo the posterior cornea in healthy subjects. The system offers approximately 98 dB sensitivity for 680 μW optical power incident on the cornea and 34,000 A-scans/s image acquisition rate. This study comprised 20 healthy subjects, aged 20 to 60 years. The thickness of the PDL, DM, and END layers was measured both with a custom, automatic segmentation algorithm and manually., Results: The boundaries and structure of the posterior corneal layers were clearly visible in the UHR-OCT images. The average thickness was measured to be 6.6 ± 1.4 μm (PDL), 10.4 ± 2.9 μm (DM), and 4.8 ± 0.4 μm (END), which agrees well with published data from ex vivo studies. Both the END and DM thickness showed minor spatial variations, whereas the PDL showed up to 2× thickness change for different locations on the same cross-sectional corneal image or over the entire imaged region of the cornea., Conclusions: Our data indicate that all three layers of the posterior cornea can be clearly visualized in vivo and their thicknesses measured precisely with UHR-OCT. Although the PDL thickness showed large spatial variations, the thickness of the DM and END layers was consistent over the entire imaged region of the cornea.

Purpose: The purpose of this study was to assess risk factors associated with soft contact lens (SCL)-related corneal infiltrative events (CIEs)., Methods: This was a single-visit, case-control study conducted at five academic centers in North America. Cases were defined as current SCL wearers with a symptomatic CIE. For each case, three age- and sex-matched controls were enrolled. Subjects completed the Contact Lens Risk Survey (CLRS), a standardized scripted medical interview, supplied a recent health history, and underwent an ocular examination. Microbial culturing of the ocular surface, SCL, and lens storage case was conducted for all cases and one of the three matched controls. Univariate and multivariate logistic regression modeling were used to assess the risk of developing a CIE., Results: Thirty cases and 90 controls 13 to 31 years of age completed the study. Corneal infiltrative event diagnosis included contact lens-associated red eye, infiltrative keratitis, and contact lens peripheral ulcer. Subjects with symptomatic CIEs were more likely to harbor substantial levels of gram-negative bioburden on the ocular surface and contact lens. Significant risk factors for developing a CIE were overnight wear of SCLs, use of multipurpose solution, rinsing SCLs with water, lens storage case older than 6 months, previous "red eye" event, use of ocular drops in the past week, and illness during the past week., Conclusions: This pilot study demonstrated feasibility of enrolling a representative pool of SCL wearers with an untreated, symptomatic CIE and assessing CIE risk factors by using standardized methods. A larger sample size is needed to determine relationships between patient-reported behaviors and exposures, microbial bioburden, and CIE development.

Purpose: To describe age and other risk factors for corneal infiltrative and inflammatory events (CIEs) in young, soft contact lens (SCL) wearers and to model the age-related risk., Methods: A multicenter, retrospective chart review of 3549 SCL wearers (8-33 years at first observed visit, +8.00 to -12.00D, oversampling <18 years) captured CIEs from January 2006 to September 2009. The review noted age, sex, SCL worn, use of lens care products, and SCL wearing history. Event diagnoses were adjudicated to consensus by reviewers masked to wearer identity, age, and SCL parameters. Significant univariate risk factors for CIEs were subsequently tested in multivariate generalized estimating equations., Results: Charts from 14,305 visits observing 4,663 SCL years yielded 187 CIEs in 168 wearers. Age was a significant nonlinear risk factor, peaking between 15 and 25 years (P < 0.008). Less than 1 year of SCL use was protective versus longer years of wear (P < 0.0003). Use of multipurpose care products (2.86×), silicone hydrogels (1.85×), and extended wear (2.37×) were significantly associated with CIEs in the multivariate model (P < 0.0001 each)., Conclusions: Patient age, years of lens wear, use of multipurpose care products, silicone hydrogels, and extended wear were all significantly associated with CIEs with SCL wear. Use of SCLs in young patients aged 8 to 15 years was associated with a lower risk of infiltrative events compared with teens and young adults. In terms of safety outcomes, SCLs appear to be an acceptable method of delivering optics designed to manage myopia progression in children and young teens in the future.

Purpose: To evaluate the change in thickness of the anterior, stromal, and posterior corneal laminae in response to hypoxia-induced corneal swelling, by means of ultrahigh-resolution optical coherence tomography (UHR-OCT)., Methods: A UHR-OCT system, operating in the 1060-nm range, was used to acquire in vivo cross-sectional images of human cornea with a 3.2x10-microm (axial x lateral) resolution in corneal tissue. Corneal edema was induced by inserting a thick, positive-powered, soft contact lens, over which the eye was closed and patched for 3 hours. Tomograms were acquired from eight non-contact-lens wearers. Baseline images were obtained before inducing corneal edema, immediately after removal of the patch and the lens, and then every 15 minutes for approximately 2 hours. All images were postprocessed with a segmentation algorithm to identify the laminae visible in the image. The apical thickness of the laminae (epithelium [EPI], epithelial-Bowman's membrane [Ep-BM] complex, stroma, and endothelial-Descemet's membrane [En-DM] complex) were determined at each time interval., Results: There was an interaction between time after removal of the hypoxic stimulus and deswelling of the layers (RM-ANOVA; P<0.001). The epithelial and stromal thickness reduced significantly with time (P=0.001; P<0.001, respectively), whereas the Ep-BM and En-DM complexes did not (P>0.50). All layers except the En-DM complex exhibited a biphasic pattern of recovery., Conclusions: UHR-OCT showed regional differences in swelling due to hypoxic provocation. On removal of the hypoxic stimulus, the rate of recovery varied between layers, and all layers except the En-DM complex exhibited a biphasic recovery.

Purpose: To investigate topographical thickness changes of the epithelium and total cornea measured with optical coherence tomography (OCT) after overnight wear of rigid gas-permeable lenses., Methods: Reverse geometry design CRT (Dk=100) rigid (test) lenses (Paragon Vision Sciences, Mesa, AZ) were randomly fitted on one eye of each of 20 neophyte subjects (mean age, 24.6 +/- 2.7 years) and the other eye was fitted with an alignment tricurve rigid lens of the same material (control). Epithelial and total corneal thickness was measured at intervals of 10 degrees across a 10-mm zone of the horizontal meridian of the cornea, before and after overnight wear. Refractive error was measured with an autorefractor. These measurements were repeated 20 and 60 minutes and 3, 6, and 12 hours after lens removal., Results: After one night of lens wear, myopia decreased in the test eye by 1.18 +/- 0.81 D, which was significantly different from baseline (P<0.001). No significant change was found in the control eye. Twelve hours after removal, two thirds of the myopic reduction was still present. Different topographical swelling patterns were induced by the two lens designs, with greatest swelling occurring in the center with the control lens and in the midperiphery with the test lenses (polynomial regression: P<0.005). Significantly greater central corneal swelling was found with the control lens than the test lens (6.9% +/- 3.1% vs. 4.9% +/- 2.0%, respectively, P=0.006). The effect on epithelial thickness differed between lenses and depended on both position and time (F(48,912)=2.3; P=0.000). Immediately after removal of the test lens, the central epithelium was 5.1% +/- 4.5% thinner than baseline, and all other locations (P<0.005 post hoc tests) and the epithelium in the midperiphery showed significant thickening (1.9% on the temporal side and 2.4% on the nasal side, both P<0.006 compared with the baseline). There were no significant changes in epithelial thickness with the control lens during the study period (post hoc tests: P>0.05)., Conclusions: The optical coherence tomograph is a sensitive instrument that can detect small changes in epithelial and corneal thickness across the entire cornea. Topographical thickness changes of the epithelium and total cornea induced by one night of reverse-geometry lens wear appear to be associated with the decrease of myopia.