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Sayantan Biswas, Vishal Jhanji, Gilda Lai, Christopher Kai-Shun Leung; Prevalence and risk factors of glaucoma in myopic subjects attending a corneal refractive surgery clinic in Hong Kong. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4276.
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© ARVO (1962-2015); The Authors (2016-present)
While glaucoma remains a relative contraindication to corneal refractive surgery, diagnosing glaucoma in myopic eyes can be challenging and the prevalence of glaucoma in myopic subjects undertaking corneal refractive surgery is unknown. This study aimed to estimate the prevalence of glaucoma in a consecutive series of myopic subjects attending the corneal refractive clinic for corneal refractive surgery in Hong Kong.
302 eyes of 152 consecutive myopic subjects (mean -6.49 D; range -2.38 to -14.88D) attending the corneal refractive clinic from October 2012 to November 2013 underwent a complete ophthalmic examination. Visual field (C40 screening test, Humphrey Field Analyzer II), RNFL imaging (Cirrus HD-OCT) and stereoscopic optic disc photography were performed. Eyes with ≥1 abnormal location in the screening test had 24-2 threshold testing. Glaucoma was defined when there was glaucomatous optic disc configuration together with OCT confirmed RNFL thinning and repeatable visual field defects. Pre-perimetric glaucoma was defined as above but with absence of visual field defects. Risk factors associated with glaucoma were computed with logistic regression analysis.
The mean age, IOP, refractive error, axial length and CCT of the 152 myopic subjects were 34.0±8.8 years, 13.3±2.3 mmHg, -6.60±2.27 D, 26.04±1.15 mm and 553.7±32.6 µm, respectively. 5 eyes (4 subjects) and 9 eyes (6 subjects) had primary open-angle glaucoma and pre-perimetric open-angle glaucoma, respectively. None of the patients had IOP ≥21 mmHg. The glaucomatous eyes had significantly smaller average RNFL thickness (78.92±9.24µm vs. 90.16±8.01, p<0.001) and CCT (533.35±34.45 vs. 555.75±29.22µm, p<0.001) and more myopic (-8.33±2.76 vs. -6.40±2.31D) compared with the non-glaucomatous eyes. Older age, higher myopia, thinner CCT, greater vertical cup-disc ratio and thinner RNFL thickness were associated with a higher risk of developing glaucoma (p≤0.042).
The prevalence of glaucoma among myopic subjects attending the corneal refractive clinic was 6.6% in which 2.6% had confirmed visual field loss. The relatively high prevalence of glaucoma in such a young age group (34 years) suggests the need of a more vigilant approach in the diagnostic evaluation of individuals seeking for refractive surgical correction.
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