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Editors Selection IGR 20-4
Clinical Forms of Glaucoma: Primary angle closure and myopia
Comment by Catherine Jui-Ling Liu 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
See also comment(s) by David Friedman •Yong and associates reported that myopia was present in 94 (22%) subjects in a study of 427 subjects with angle closure; 11 (2.6%) among them were high myopia (£ -5.00D), a figure similar to what had been reported by Chakravarti and Spaeth.1 A new finding of this study is that myopic angle-closure patients had longer axial length (AL) and vitreous cavity length than their hyperopic and emmetropic counterparts, but had comparable anterior chamber depth (ACD). These findings are consistent with our current understanding of risk factors for angle closure and morphology of myopic eyes.
Assessment of ACD during slit-lamp biomicroscopy is useful in screening for angle closure, even for eyes with myopia
What the authors did not demonstrate is the mechanisms for angle closure in these myopic eyes. All subjects had received laser iridotomy, but patients with previous iridoplasty were excluded. Among the 11 high myopic patients listed in Table 3, three aged 70 years or older had AL shorter than the average (21.33 mm, 21.71 mm, and 21.16 mm, respectively), which leads one to reason that these patients actually are hyperopic angle-closure by nature who developed myopia late in life (possibly after iridotomy) due to cataract development. A figure displaying AL distribution of all the myopic eyes would help readers better understand these patients' ocular status. Besides, which eye of each subject was chosen for analysis (the eye with greater myopia? Higher presenting IOP? Or worse optic nerve?) was not mentioned, which could potentially bias the study results.
Hyperopia is a risk factor for angle closure which is prevalent in elderly Chinese born before 1950,2 but an increasingly high prevalence of myopia has been shown in China, Singapore, and Taiwan in recent decades.3-5 Although on average myopic eyes have deeper ACD than hyperopic eyes, the study by Yong and associates suggests that assessment of ACD during slit-lamp biomicroscopy is useful in screening for angle closure, even for eyes with myopia.
References
- Chakravarti T, Spaeth GL. The prevalence of myopia in eyes with angle closure. J Glaucoma 2007;16:642-643.
- Quigley HA, Broman AT. The number of persons with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006;90:262-267.
- He M, Zeng J, Liu Y, et al. Refractive error and visual impairment in urban children in southern China. Invest Ophthalmol Vis Sci 2004;45:793-799.
- Saw SM, Carkeet A, Chia KS, et al. Component dependent risk factors for ocular parameters in Singapore Chinese children. Ophthalmology 2002;109(11):2065-2071.
- Lin LL, Shih YF, Hsiao CK, Chen CJ. Prevalence of myopia in Taiwanese schoolchildren: 1983 to 2000. Ann Acad Med Singapore 2004;33(1):27-33.
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