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

Abstract Purpose To compare anterior segment parameters in Chinese and Japanese subjects using anterior segment optical coherence tomography (ASOCT) and to determine if the associations between these parameters and angle closure vary between the two ethnic groups. Methods We conducted a case‐control study among 117 Japanese and 102 Chinese patients with primary angle closure (PAC) or primary angle closure glaucoma (PACG); and 117 Japanese and 176 Chinese controls. All participants underwent A‐scan biometry and ASOCT imaging (Visante, Carl Zeiss Meditec, Dublin, Ca). ASOCT‐derived biometric parameters were compared between groups. Multivariate analysis was performed to determine predictors of angle opening distance at 750µm from the scleral spur (AOD750). Results Japanese were older (p<0.001) and consisted of more females (p<0.001). Age and gender adjusted analysis of covariance showed that Japanese eyes with angle closure had a significantly shallower anterior chamber depth (p=0.015), shorter axial length (p<0.001), greater lens thickness (p<0.001), lens vault (LV) (p=0.001) and iris curvature (I‐Curv) (p<0.001), and a smaller anterior chamber area (p=0.044) and volume (p=0.028); but no significant difference was noted for anterior chamber width (ACW). In Japanese, the predictors of AOD750 were LV (p=0.004), ACW (p=0.049) and ICurv (p=0.017); in Chinese, only the LV (p<0.001) was a determinant factor. Conclusion Japanese eyes with angle closure were smaller, with thicker lenses. LV is an important factor for angle closure in both races. These results suggest differing mechanisms of angle closure pathogenesis between the two ethnic groups.