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Ye Elaine Wang, YINGJIE LI, Dandan Wang, Mingguang He, Shan Lin; Inter-ethnicity Comparison of Anterior Chamber Biometry and Iris Measurements between Narrow Angle and Open Angle Cohorts Using ASOCT. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2254.
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© ARVO (1962-2015); The Authors (2016-present)
To assess differences in anterior segment biometry and iris parameters among narrow and open angle American Caucasians, American Chinese and mainland Chinese, in order to elucidate potential inter-ethnic differences in the course of angle closure development.
Three gender- and age-matched Caucasians, American Chinese, and mainland Chinese cohorts were enrolled. Subjects in each ethnic group were divided into narrow and open angle subgroups. Narrow angles were defined as posterior trabecular meshwork not visible for ≥2 quadrants on gonioscopy. ASOCT and customized software were utilized to image and calculate the anterior chamber biometry and iris measurements.
Data from 120, 116, and 116 subjects were available for Caucasian, American Chinese, and mainland Chinese, respectively. The open angle cohort had 96, 80, and 86; while the narrow angle cohort had 24, 36, and 30 Caucasian, American Chinese and mainland Chinese subjects, respectively. After multiple linear regression adjusting for confounders, ethnic Chinese showed significantly smaller anterior chamber width (ACW), anterior chamber depth (ACD), anterior chamber area (ACA), and anterior chamber volume (ACV) in both the open (p<0.0001; p<0.0001; p=0.0210; p=0.001; respectively) and narrow angle cohorts (p<0.0001; p=0.0168; p=0.016; p=0.0076; respectively). For iris measurements, only iris area (Iarea) was found to be significantly greater in both open angle (p=0.0098) and narrow angle (p=0.0228) ethnic Chinese subjects. Iris thickness at 750μm from the scleral spur (IT750), and pupil diameter (PD) were only found to be significantly greater in Chinese with open angles (p=0.0122). Iris curvature (Icurv) and lens vault (LV) were not significantly different between Caucasians and Chinese regardless of whether they had narrow or open angle.
Both open and narrow angle ethnic Chinese have smaller ACW, ACD, ACA, and ACV than Caucasians counterparts. This can in part explain the observed difference in the prevalence of angle closure between Chinese and Caucasians. Since within the narrow angle group, no significant inter-ethnic differences were detected for iris parameters except for iris area, other factors such as iris root insertion location, ciliary body size and angulation, and genetic background may contribute to the increased risk for angle closure in ethnic Chinese.
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