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Brien A Holden, Mingguang He, Monica Jong, Wayne Li, Serge Resnikoff, Ian George Morgan, Earl L Smith; Vision Impairment in Highly Myopic Eyes: the ZOC-BHVI High Myopia Study. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3635.
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To assess vision impairment in highly myopic eyes and its relationship with various ocular parameters and the presence of retinal pathology.
Nine hundred and seventeen participants aged 7 to 70 years with myopia ≥6.00D (both eyes), mean age 22.1 ± 12.5 years, were recruited from the Zhongshan Ophthalmic Centre clinics. Exclusion criteria were systemic or ocular conditions including syndromic myopia, previous ocular surgery or myopia treatment. Ocular parameters measured in both eyes comprised refraction, best corrected visual acuity (BCVA), axial length (AL) corneal curvature, anterior chamber depth (ACD) intraocular pressure (IOP). Retinal findings were recorded as A. normal; B. abnormal (including retinal break, macular oedema, posterior staphyloma, retinal detachment). Percent of the total population was used to calculate prevalence of retinal pathology for each ocular measure. Vision was classified as: Normal (≥ 1.0); Mild Vision Impairment (<1.0 to <0.3); Moderate Vision Impairment (0.3 to ≥0.1); Severe Vision Impairment (<0.1 to ≥0.05) and Blindness (<0.05). The eyes were divided into a better vision (BV) group, BCVA ≥ 0.5 (6/12) (mean 0.91+/-0.16) and a worse vision (WV) group, < 0.5 BCVA, (mean 0.29+/-0.11). Linear mixed model and logistic regression robust estimation of variance were used to evaluate for significant influences (p <0.05).
Data from 1686 eyes (843 participants, 442 female) were analysed. The spherical equivalent (SE) was -9.30 ± 2.90 D (range: -6.00 to -29.80 D) and axial length, 27.2 ± 1.4 mm (range 23.8 to 31.8 mm). Thirty four percent of subjects had 1 myopic parent, 19% had two. 37.1% of the eyes had mild vision impairment; 4.5% had moderate vision impairment; 0.6% were blind. Myopic retinal pathology was seen in 13% (224) of eyes. On average the BCVA < 0.5 group had -5.57D more myopia (p = < 0.01), 0.28 mm thicker ocular lenses (p< 0.01), 1.6 mm greater axial lengths (p < 0.01); -0.19 mm shallower AC depths; more likely to have retinal pathology 35% v 11% and 7.7 years older.
Vision impairment was associated primarily with the severity of high myopia and the presence of retinal pathology, and to a lesser extent, increased ocular lens thickness and shallower anterior chamber depth. Vision impairment was not as strongly influenced by axial elongation. In 65% of cases, vision impairment occurred in the absence of obvious retinal pathology.
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