Structure-Function Relationship in Keratoconus: Spatial and Depth Vision

Purpose: The purpose of this study was to determine changes in spatial and depth vision with increasing severity of keratoconus and to model the structure-function relationship to identify distinct phases of loss in visual function with disease severity. Methods: Best-spectacle corrected, monocular high-contrast visual acuity, contrast sensitivity function (CSF) and stereoacuity of 155 cases (16–31 years) with mild to advanced bilateral keratoconus was determined using standard psychophysical tests. Disease severity was quantified using the multimetric D-index. The structure-function relationship was modeled using linear, positive exponential, negative exponential, and logistic nonlinear regression equations. Results: The logistic regression model explained the highest proportion of variance for spatial vision, without bias in the residual plots (R2 ≥ 66%, P 400 arc second); both were significantly poorer than controls (approximately 30 arc second). Conclusions: Vision loss in keratoconus varies with the visual function parameter tested. Contrast sensitivity may be an earlier indicator of spatial vision loss than visual acuity. Depth perception is significantly deteriorated from very early stages of the disease. Translational Relevance: The study outcomes may be used to forecast longitudinal vision loss in keratoconus and to apply appropriate interventions for timely preservation/enhancement of vulnerable visual functions

Biocompatibility and Comfort during Extended Wear of Mel4 Peptide-Coated Antimicrobial Contact Lenses

(1) Purpose: This study aimed to investigate the effects of Mel4 antimicrobial contact lenses (MACL) on the ocular surface and comfort during extended wear. (2) Methods: A prospective, randomised, double-masked, contralateral clinical trial was conducted with 176 subjects to evaluate the biocompatibility of contralateral wear of MACL. The wearing modality was 14-day extended lens wear for three months. The participants were assessed at lens dispensing, after one night, two weeks, one month and three months of extended wear and one month after study completion. (3) Results: There were no significant differences (p > 0.05) in ocular redness or palpebral roughness between Mel4 and control eyes at any of the study visits. There was no significant difference (p > 0.05) in corneal staining between Mel4 and control eyes. There were no significant differences in front surface wettability or deposits or back surface debris (p > 0.05). No statistically significant differences (p > 0.05) were found in comfort, dryness, CLDEQ-8 scores lens or edge awareness. There was no evidence for delayed reactions on the ocular surface after cessation of lens wear. (4) Conclusion: The novel MACLs showed similar comfort to control lenses and were biocompatible during extended wear. Thus, these lenses were compatible with the ocular surface

Effect of Antimicrobial Contact Lenses on Corneal Infiltrative Events:A Randomized Clinical Trial

Purpose: To determine whether Mel4-coated antimicrobial contact lenses (MACLs) can reduce the incidence of corneal infiltrative events (CIEs) during extended wear. Methods: A prospective, randomized, double-masked, single-center, contralateral, extended contact lens wear clinical trial was conducted with 176 subjects. Each participant was randomly assigned to wear a MACL in one eye and an uncoated control contact lens in the contralateral eye or an extended-wear biweekly disposable modality for 3 months. The main outcome measures were the incidence of CIEs per 100 eye-months, identification of the microbial types colonizing the contact lenses or eyes at the time of the CIEs, and their susceptibility to Mel4. Results: Nine participants (5.1%) experienced unilateral CIEs; six participants had contact lens acute red eye, and three participants had infiltrative keratitis. The incidence rate for CIEs (0.4 events per 100 participant months; 1.7%) in the Mel4-coated lenses (test) was 69% less than that of the control lenses (1.3 events per 100 participant months; 3.4%; P = 0.29). All Gram-negative bacteria isolated from lenses and lids of participants with CIEs (Citrobacter diversus, Acinetobacter haemolyticus, and Acinetobacter lwoffii) were susceptible to Mel4 peptide; minimum inhibitory concentrations ranged from 15.6 to 62.5 µg/mL. Reduction of adhesion of these bacteria by Mel4-coated lenses ranged from 2.1 to 2.2 log10 colony-forming units/lens. Conclusions: MACLs had the capacity to reduce CIEs by at least 50% compared with uncoated control lenses during extended wear over 3 months; however, due to the relatively low rates of CIEs, the reduction was not statistically different compared with control lenses. Translational Relevance: This study provides evidence that antimicrobial contact lenses have the potential to reduce the incidence of corneal infiltrative events during extended wear

In Vivo Confocal Microscopic Corneal Images in health and disease with an emphasis on extracting features and visual signatures for corneal diseases: A review study

There is an evolution in the demands of modern ophthalmology from descriptive findings to assessment of cellular level changes by using in vivo confocal microscopy. Confocal microscopy, by producing grey-scale images, enables a microstructural insight into the in vivo cornea in both health and disease, including epithelial changes, stromal degenerative or dystrophic diseases, endothelial pathologies, and corneal deposits and infections. Ophthalmologists use acquired confocal corneal images to identify health and disease states and then to diagnose which type of disease is affecting the cornea. This paper presents the main features of the healthy confocal corneal layers, and reviews the most common corneal diseases. It identifies the visual signature of each disease in the affected layer and extracts the main features of this disease in terms of intensity, certain regular shapes with both their size and diffusion, and some specific region of interest. These features will lead towards the development of a complete automatic corneal diagnostic system which predicts abnormalities in the confocal corneal data sets

Technology needs for corneal transplant surgery

Corneal transplant surgery has undergone numerous modifications over the years with improvements in technique, instrumentation and eye banking. The main goals of corneal transplantation are achieving excellent optical clarity with long-term graft survival. Penetrating, anterior and posterior lamellar surgery along with femtosecond laser technology have partially met these goals, but outcomes are often unpredictable and surgeon dependent. Technology to predictably separate stroma from Descemet's membrane, techniques to minimize endothelial cell loss, improvements in imaging technology and emerging techniques like laser welding that might replace suturing, eventually making corneal transplantation a refractively predictable procedure are on the wish list of the cornea surgeon