Background: To assess the distribution of iris structural measurements among American Caucasians, American Chinese and mainland Chinese aged 40years and over, in order to determine associated factors of increased risk for angle closure in Chinese.
Design: Prospective multicentre cross-sectional study.
Participants: Four gender- and age-matched cohorts: Caucasians, American Chinese, Southern Chinese from Guangzhou and Northern Chinese from Beijing were enrolled in this study.
Methods: Anterior segment optical coherence tomography was utilized to image the anterior chamber. Customized software was used to calculate the related parameters from anterior segment optical coherence tomography images.
Main outcome measures: Iris thickness at 750µm from the scleral spur, iris curvature, iris area, pupil diameter.
Results: Data from 121, 124, 121 and 120 subjects were available for American Caucasian, American Chinese, Southern and Northern Mainland Chinese subjects, respectively. The Chinese cohorts did not differ with regard to any of the parameters. Multiple linear regressions indicated that Caucasians had thinner iris thickness at 750µm from the scleral spur and smaller iris area than Chinese after controlling for potential confounders. Female Caucasians had thinner irides (P=0.015) and smaller iris area (P=0.001) than male Caucasians. Female Chinese tended to have more convex irides (P=0.021) than male Chinese. Pupil size was inversely associated with age (P<0.001) in both ethnicities.
Conclusions: In dark conditions, Chinese have thicker irides and greater iris area than Caucasians independent of pupil size. Among Chinese, more convex irides in women may account for the higher rate of narrow angles identified in this segment of the Chinese population.
© 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.