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Editors Selection IGR 18-1

Clinical Forms of Glaucoma: Primary Angle Closure and Myopia

Comment by Ki Ho Park on:

The authors performed a simulation study on age-specific prevalence of occludable angle (OA) by different rates of myopia (from 10% to 60%) in a Chinese population based on data collected in the Liwan Eye Study. The purpose of the authors’ study was to determine whether the increasing prevalence of myopia in the East Asian population would lead a reduction in the prevalence of OA.

The results of the study were not what were generally expected. The projected prevalence of OA in the cohorts with myopia prevalence of 10, 20, 40, 50, and 60% was 11.1, 10.7, 9.9, 9.3, and 9.6%, respectively, which indicate that the increasing prevalence of myopia has minimal impact on the prevalence of OA.

The results are in line with a previous report by a Singapore group, Yong et al. according to which, among 427 angle-closure cases, a quarter of them manifested myopia, although these myopic angle closure cases tended to have longer axial and vitreous cavity lengths in comparison with emmetropic and hyperopic angle closure cases.

These two papers might explain the phenomenon that although the Chinese population has a much higher prevalence of myopia compared with European populations, they also have a higher prevalence of angle closure. So even though the prevalence of myopia is increasing in the East Asian region, (e.g., among teenagers between 16 and 18 years, myopic prevalence in Taiwan increased from 74% in 1983 to 84% in 2000), primary angle-closure glaucoma might deserve the same level of public health attention in the future.

The limitation of this study is that as seen in the simulation groups, the ranges of average spherical equivalent and the average axial length were relatively small: from 0.62 D to -0.81 D and from 23.1 to 23.6 mm, respectively, in which cases, lenticular myopia rather than axial myopia might have contributed in part. In addition it would have been better to include a group or groups representing a higher rate of myopia (e.g., 70% and/or 80%) in the simulation.

The increasing prevalence of myopia has minimal impact on the prevalence of occludable angle.

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