[An epidemiological study on the prevalence of the narrow chamber angle in Japanese]

Primary angle-closure glaucoma (PACG) has been reported to be more prevalent in Orientals than in Caucasians. However, our knowledge about the epidemiology of narrow angle and PACG in Orientals is still extremely limited. To determine the prevalence of narrow angle and PACG in Japanese, we carried out gonioscopic and oculometric examinations as a part of the first nationwide, multicenter glaucoma survey in Japan. We also estimated the angle width by means of van Herick's method to assess the efficacy of this method in detecting narrow angle. Of 1,979 inhabitants 40 years or older of a town in Gifu Prefecture, 585 (29.6%) participated in the study and underwent tonometric, gonioscopic and oculometric examinations. The width of the angle was estimated by van Herick's method prior to gonioscopy. Of the group tested, the prevalence of grade 0 to 2 angles (Shaffer's classification) was found in 8.0%, which was significantly more frequent than among Caucasians. The prevalence of grade 1 or narrower angle and PACG was 2.6% and 0.3%, respectively, neither of which was significantly different from rates reported among Caucasians. Using the gonioscopic determination as a gold standard, van Herick's method was noted to have a sensitivity of 77% and a specificity of 94% in identifying eyes with the angle of grade 2 or narrower, while both the sensitivity and specificity of this method were above 90% in detecting an angle of grade 1 or narrower. It was concluded that van Herick's method was useful in detecting the extremely narrow angle.