Anterior Chamber Depth and the Risk of Primary Angle Closure in Two East Asian Populations

Abstract

Abstract: : Purpose: To evaluate the risk of peripheral anterior synechiae (PAS) attributable to primary angle closure at varying anterior chamber depth (ACD) in two East Asian populations. Methods: Participants were from 2 cross-sectional community based glaucoma surveys of people aged 40 years and older from the Hovsgol province of Mongolia, and the Tanjong Pagar district of Singapore. Central ACD (corneal epithelium to anterior lens epithelium) and central corneal thickness were measured at the slit-lamp by optical pachymetry. "True" ACD (from the endothelial surface of the cornea to the anterior surface of the lens) was calculated by subtracting the corneal thickness from the central ACD measurement. Presence or absence of PAS and angle closure was determined by manipulative and indentation gonioscopy. Results: A total of 1936 subjects comprising of 942 Mongolians and 994 Chinese Singaporeans were included in the study. ACD was found to be significantly shallower in women than men of all ages and decreased with age. The risk of PAS increased at shallower ACD in both populations. The odds ratio of PAS among Singaporeans was 1.8 (95% CI 0.5-6.4) at ACD of 2.60-2.79mm, 5.0 (95% CI 1.7-17.3) at ACD of 2.20-2.39mm, 6.0 (95% CI 2.1-23) at ACD 2.0-2.19mm and 16.5 (95% CI 1.5-182) at ACD<1.80mm. The corresponding odds ratios for Mongolians were 0.93 (95% CI 0.1-15.0) at ACD of 2.60-2.79mm, 3.7 (95% CI 0.4-33.6) at ACD of 2.20-2.39mm, 17.8 (95% CI 2.2-142.7) at 2.0-2.19mm and 174 (95% CI 15.7-1927) at ACD<1.80mm. Multiple logistic regression showed that steep iris profile was related to the presence of PAS in Singaporeans, but not in Mongolians. Conclusions: In Chinese Singaporeans and Mongolians, the risk of PAS was found to increase with decreasing ACD. The traditional belief that shallow anteior chambers carry a significant risk of angle closure appears valid in East Asian eyes.

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