Objective: To determine the prevalence of primary angle-closure glaucoma (PACG), primary angle closure (PAC), and PAC suspect (PACS) in an urban population, and to compare prevalence and associated risk factors with a rural population. Design: Population-based cross-sectional study. Participants: Four thousand eight hundred subjects 40 years or older were selected from Chennai city using multistage random cluster sampling. Intervention: All subjects had a complete ophthalmic examination that included logarithm of the minimum angle of resolution visual acuity, applanation tonometry, gonioscopy, grading of lens opacities, dilated fundus examination, optic disc photography, and visual fields. Main Outcome Measures: Glaucoma was diagnosed using the International Society of Geographical and Epidemiological Ophthalmology classification. Results: Three thousand eight hundred fifty (80.2%) responded; 34 subjects (17 female, 17 male) had PACG (0.88%; 95% confidence interval [CI], 0.60-1.16). The mean intraocular pressure (IOP) was 26.0±14.9 mmHg. Five subjects (14.7%) had been previously diagnosed to have glaucoma, 1 of whom had undergone glaucoma surgery and 2 of whom had been diagnosed to have open-angle glaucoma. Two subjects (5.9%) were bilaterally and 3 subjects (8.8%) were unilaterally blind. One hundred six subjects (2.75%; 95% CI, 2.01-3.49) were diagnosed to have PAC (62 female, 44 male). Thirty-nine subjects (36.8%) had presenting IOP > 24 mmHg, 83 (78.3%) had peripheral anterior synechiae, and 16 (15.1%) had both. Two hundred seventy-eight subjects (7.24%; 95% CI, 6.38-8.02) had PACS (183 female, 95 male). Prevalences of PACG and PACS were similar in the urban and rural populations. Primary angle closure prevalence was higher in the urban population (P<0.0001). Primary angle closure and PACG were positively associated with increasing age and IOP in both populations and were more common in rural women (odds ratio [OR], 4.3; 95% CI, 2.2-8.3). Association with hyperopia was seen only in the urban population (OR, 2.0; 95% CI, 1.4-2.8). Conclusions: Prevalences of PACG and PACS were similar in the rural and urban populations; PAC was more common in the urban population. In both groups, the disease was asymptomatic. Poor detection rates were probably due to lack of gonioscopy as a routine part of an eye examination.
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