Optic neuropathy may induce vision loss in highly myopic eyes

Optic neuropathy is the cause of vision impairment in 9.0 percent of eyes of highly myopic patients, according to a study. This rate is lower than the prevalence of myopic macular degeneration (MMD) as reason behind vision loss, which stands at 18.9 percent.

“Notably, optic neuropathy became a significant contributor to vision impairment in more advanced high myopia, reaching 36 percent in the group with refractive error of <–15.0 dioptres (D),” the authors said.

This population-based study examined the prevalence and causes of loss of visual acuity and visual field in highly myopic eyes. A total of 4,439 patients went through ophthalmological and systemic examinations including frequency doubling technology perimetry. High myopia was characterized by a refractive error of ≤–6 D or axial length >26.0 mm.

Overall, 212 highly myopic eyes from 154 participants (mean age 56.2 years, mean refractive error ‒9.87, mean axial length 27.2 mm) were assessed. Moderate-to-severe vision impairment (MSVI) was observed in 40 eyes (18.9 percent, 95 percent confidence interval [CI], 13.6‒24.2) and blindness in 10 (4.7 percent, 95 percent CI, 1.8‒7.6).

MMD accounted for MSVI and blindness in 29 out of 50 eyes (58 percent), while age-related macular degeneration and branch macular retinal vein occlusion caused vision impairment in one eye each (2 percent).

Secondary causes for MSVI and blindness were MMD (four out of 50, 8 percent) and optic nerve atrophy (14 out of 50, 28 percent), which was further categorized into nonglaucomatous optic atrophy (NGOA; nine out of 50, 18 percent) and glaucomatous optic atrophy (GOA; 5 out of 50, 10 percent).

MMD prevalence as the cause of vision loss significantly rose from 1/61 (1.6 percent) in the refractive error group of ‒6.00 to ≥–7.00 D to 16/25 (64 percent) in the group of <–15.0 D. Higher MMD prevalence resulted in greater myopic refractive error (p<0.001) and higher possibility of having concomitant optic neuropathy (p<0.001).

Optic neuropathy prevalence as the cause of vision impairment also rose from 0/61 (0 percent) in the refractive error group of –6.00 D to ≥–7.00 D to 9/25 (36 percent) in the group of <–15.0 D. Higher optic neuropathy prevalence was associated with older age (p=0.02) and more myopic refraction (p<0.001).