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Guangming Jin, Xiaohu Ding, Xinxing Guo, Billy Heung Wing Chang, Mingguang He; The predicted age-specific prevalence of occludable angle with increased prevalence of myopia in a Chinese population. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2932.
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Myopia is associated with longer eyes and presumably deeper anterior chamber depth (ACD), which prevents the eye from developing primary angle closure glaucoma (PACG). The impact of the increased prevalence of myopia on this condition remains unknown. We conducted a simulation study to predict the prevalence of occludable angle (OA), an indicator of PACG, with the increasing prevalence of myopia in China.
Data from a population-based study which consisted of 1405 subjects ≥50 years in Liwan District, Guangzhou were used. Refraction was collected using a handheld autorefractor (ARK-30; Nidek Corp., Gamagori, Japan). ACD was measured before dilation by A-mode ultrasound (Echoscan US1800; Nidek, Corp.) and gonioscopy was performed by a trained ophthalmologist. Spherical equivalence (SE) was calculated as sphere+1⁄2 cylinder, myopia was defined as SE<-0.5D; OA was defined as one in which >270° of the posterior trabecular meshwork was hidden from view during static gonioscopy. After excluding subjects with insufficient data or evidence of cataract surgery, cohorts with myopia prevalence of 10%, 20%, 40%, 50% and 60% were simulated by sampling according to the multinomial distribution from the database using R software. The mean ACD and OA rates of each cohort were calculated. Multivariate logistic regression models using the ACD as an intermediate variable were used to fit a predictive model of OA prevalence.
Data of the right eyes from 1160 subjects were qualified for analysis. The mean age was 64.29.5 years, with 43% being male. The prevalence of myopia and OA were 32.5% (95% confidence interval [CI], 29.8-35.3%) and 10.3% (95% CI, 8.7-12.2%) respectively. ACD decreased with age but was affected by the prevalence of myopia. The mean ACD increased from 2.68mm to 2.74mm with the prevalence of myopia increasing form 10% to 60%.<br /> The predicted prevalence of OA in cohorts with myopia prevalence of 10%, 20%, 40%, 50% and 60% were 11.1% (95%CI, 10.5-11.8%), 10.7% (95%CI, 10.1-11.4%), 9.9% (95%CI, 9.3-10.5%), 9.3% (95%CI, 8.8-9.9%) and 9.6% (95%CI, 8.9-10.3%) respectively. A mild reduction in the prevalence of OA is associated with the increasing prevalence of myopia.
The increasing prevalence of myopia has minimal impact on the prevalence of OA. Prevalence of PACG may remain high in the Chinese population.
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