Investigating the determinants of iridolenticular contact area: a novel parameter for angle closure.

BACKGROUND/AIMS: To identify ocular determinants of iridolenticular contact area (ILCA), a recently introduced swept-source optical coherence tomography (SSOCT) derived parameter, and assess the association between ILCA and angle closure. METHODS: In this population-based cross-sectional study, right eyes of 464 subjects underwent SSOCT (SS-1000, CASIA, Tomey Corporation, Nagoya, Japan) imaging in the dark. Eight out of 128 cross-sectional images (evenly spaced 22.5° apart) were selected for analysis. Matlab (Matworks, Massachusetts, USA) was used to measure ILCA, defined as the circumferential extent of contact area between the pigmented iris epithelium and anterior lens surface. Gonioscopic angle closure (GAC) was defined as non-visibility of the posterior trabecular meshwork in two or more angle quadrants. RESULTS: The mean age of subjects was 62±6.6 years, with the majority being female (65.5%). 143/464 subjects (28.6%) had GAC. In multivariable linear regression analysis, ILCA was significantly associated with anterior chamber width (ß=1.03, p=0.003), pupillary diameter (ß=-1.9, p<0.001) and iris curvature (ß=-17.35, p<0.001). ILCA was smaller in eyes with GAC compared with those with open angles (4.28±1.6 mm2 vs 6.02±2.71 mm2, p<0.001). ILCA was independently associated with GAC (ß=-0.03, p<0.001), iridotrabecular contact index (ß=-6.82, p<0.001) or angle opening distance (ß=0.02, p<0.001) after adjusting for covariates. The diagnostic performance of ILCA for detecting GAC was acceptable (AUC=0.69). CONCLUSIONS: ILCA is a significant predictor of angle closure independent of other biometric factors and may reflect unique anatomical information associated with pupillary block. ILCA represents a novel biometric risk factor in eyes with angle closure.

Clinical operational considerations and responses to lockdown and reopening in the Covid-19 pandemic: experience of a tertiary ophthalmology centre in Singapore.

BACKGROUND: Much has been written on infection control and clinical measures for ophthalmic institutions and departments to cope with the COVID-19 pandemic. However, few articles have detailed implementation plans to manage lockdowns and subsequent re-openings. In this article, specific operational responses and their outcomes in a large tertiary ophthalmology centre are described. METHOD: Through a concerted effort led by a dedicated task force, the Singapore National Eye Centre (SNEC) planned and executed an operational transformation to respond to the restrictions imposed on healthcare delivery during a national lock down. A carefully calibrated re-starting of services was carried out with the subsequent phased reopening of the country, taking into consideration unique constraints faced at that time. Strategies for operating in the new normal environment were also developed. RESULTS: Outpatient attendances were safely and expediently reduced by 70% (8749 vs. 29,311) and 82% (5164 vs. 29,342) in April and May 2020, respectively, compared to the corresponding months in 2019. A correspondingly large reduction in surgical load was also achieved through a similar triaging and prioritization system. Through optimizing the center's use of space and time, as well as expanding on new models of care, a return to pre-pandemic patient load was achieved 3 months into the phased reopening of the country, and subsequently exceeded in the following months. CONCLUSION: The lessons gleaned from SNEC's experience may be useful for institutions currently facing the same challenges, and for future responses to COVID-19 resurgences or other pandemics.

Comparison of keratometric and pachymetric parameters with Scheimpflug imaging in normal and keratoconic Asian eyes.

PURPOSE: To evaluate the keratometric and pachymetric parameters of keratoconic corneas of Asian eyes with the Scheimpflug imaging camera. PATIENTS AND METHODS: This is a cross-sectional study of 22 eyes with Amsler-Krumeich stage 1 keratoconus and 48 eyes from normal subjects conducted in a tertiary eye hospital. A rotating Scheimpflug imaging system, the Pentacam, was used to evaluate all eyes for tomographic parameters, as well as pachymetric progression indices (PPI) and Ambrósio relational thickness (ART). RESULTS: All PPI and ART parameter values were significantly different between study and control groups. Cornea minimum radius of curvature, absolute distance from corneal apex to thinnest location, as well as the distance from corneal apex to thinnest location in Y-axis also demonstrated statistically significant differences. The mean ART values for keratoconus eyes were 241 µm (ART-maximum) and 352 µm (ART-average), falling within previously reported best cutoff values for detecting keratoconus. On receiver operating characteristics curve analysis, the area under the curve values were highest for PPI and ART parameters. CONCLUSION: There are significant differences in tomographic parameters between stage 1 keratoconic and normal Asian eyes. Pachymetric indices such as the PPI and the ART index can serve as additional tools in differentiating keratoconic from normal eyes. The findings validate the usefulness of the ART in identifying keratoconic eyes in Asians.