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Editors Selection IGR 12-2

Clinical Forms of Glaucoma: Primary angle closure and myopia

Comment by David Friedman on:

56512 Myopia in Asian Subjects with Primary Angle Closure: Implications for Glaucoma Trends in East Asia, Yong KL; Gong T; Nongpiur ME et al., Ophthalmology, 2014; 121: 1566-1571

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Yong and colleagues recruited 427 individuals with angle closure from the Singapore National Eye Center clinics to assess the association of primary angle closure (PAC) with refractive errors. The actual recruitment and patient selection process is not stated so it is difficult to know how this subset of angle closure patients compares to the overall population of those with angle closure in Singapore. Furthermore, Singapore overall has very high rates of myopia, so findings from this single site study may not apply to other locations where myopia is less common.

The study population included suspects (PACS), those with primary angle closure (PAC) and those with PAC glaucoma (PACG) as well as individuals who had had an acute primary angle closure attack (APAC). Refractive error was determined by autorefraction. About half of all subjects were hyperopic, and about one out of five subjects was more than 0.50 diopters myopic. 6.6% and 2.6% of subjects had between -2D and -5D of myopia and more than -5D of myopia, respectively.

When assessing differences in biometric parameters comparing myopes to emmetropes and hyperopes, anterior chamber depth, central corneal thickness and lens thickness were all similar across the groups. Myopes had longer axial and vitreous lengths, and borderline larger lens vault.

While the authors state that nearly one in four subjects with angle closure are myopic, the fact is that this population may not be representative, and some of the myopia is almost certainly due to cataract among this older population. Furthermore, the cutoff of -0.5D is low and a alternative cutoffs were not provided.

The authors strongly recommend (and I agree) that gonioscopy still be performed when assessing individuals with myopia, even high myopes

Previous reports have consistently found that a small proportion (1.5 to 3%) of those with angle closure have myopia of -5D or greater. This appears to continue to be the case in Singapore and the fact that other factors including anterior chamber depth were similar in myopes and hyperopes with angle closure indicates that vitreous chamber depth elongation likely explains why some myopes can still have angle closure. Based on the findings the authors strongly recommend (and I agree) that gonioscopy still be performed when assessing individuals with myopia, even high myopes.

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