Angle-closure glaucoma in Asians: comparison of biometric and anterior segment parameters between Japanese and Chinese subjects

To compare anterior segment parameters in Chinese and Japanese subjects with angle closure using anterior segment optical coherence tomography (ASOCT). One hundred and forty-two Japanese and one hundred and ninety-two Chinese subjects with primary angle closure (PAC) or primary angle-closure glaucoma (PACG) were recruited. All participants underwent A-scan biometry and ASOCT imaging (Visante, Carl Zeiss Meditec, Dublin, CA, USA). Customized software was used to measure ASOCT parameters in horizontal ASOCT scans. The parameters were compared, and multivariate analysis was performed to determine predictors of angle opening distance at 750 mu m from the scleral spur (AOD750). Ethnic difference evaluated by multiple linear regression adjusted for age, gender, spherical equivalent, pupil diameter, and axial length showed that Japanese angle-closure subjects had significantly shallower anterior chamber depth (ACD;beta = -0.3, p < 0.001), smaller anterior chamber area (ACA; beta = -0.21, p = 0.02) and volume (ACV; beta = -0.19, p = 0.01), greater lens vault (LV, beta = 0.3, p < 0.001), lens thickness (LT; beta = 0.48, p < 0.001), greater iris area (IArea; beta = 0.19, p = 0.01), and more curved iris (ICurv; beta = 0.16, p = 0.04). The significant determinants of AOD750 were iris thickness (IT; beta = -0.21, p = 0.04), ICurv (beta = -0.17, p = 0.04), pupil diameter (PD; beta = -0.34, p = 0.001) and ACV (beta = 0.32, p < 0.001) in Japanese; and IT (beta = -0.25, p = 0.001), ACV (beta = 0.37, p < 0.001), PD (beta = -0.26, p = 0.001), and LV (beta = -0.18, p = 0.03) in Chinese. Compared to Chinese, Japanese angle-closure eyes have smaller and more crowded anterior segment with thicker lenses. ACV, IT, and PD are important factors for angle width in both races. These results suggest possible ethnic differences in angle-closure mechanism(s).