Visual consequences of refractive errors in the general population

Abstract

Objective: To study the frequency and causes of visual impairment in relation to refractive error.

Design: Population-based cohort study.

Participants: A total of 6597 participants from Rotterdam Study I (baseline and 4 follow-up examinations) and 2579 participants from Rotterdam Study II (baseline and 2 follow-up examinations), all 55 years or older, were included.

Methods: Participants underwent an extensive ophthalmic examination, including best-corrected visual acuity and objective refraction, fundus photography, visual field perimetry, and optical coherence tomography imaging of macula and optic disc. We calculated cumulative risks and odds ratios of visual impairment for various refractive error categories and determined causes by using all screening information as well as medical records.

Main outcome measures: Unilateral and bilateral low vision (World Health Organization [WHO] criteria, VA < 0.3 and VA ≥ 0.05; United States (US) criteria, VA < 0.5 and VA ≥ 0.1) and blindness (WHO criteria, VA < 0.05; US criteria, VA < 0.1).

Results: Cumulative risks of visual impairment ranged from virtually 0 in all refractive error categories at 55 years of age to 9.5% (standard error, 0.01) for emmetropia and 15.3% (standard error, 0.06) for high hyperopia to 33.7% (standard error, 0.08) for high myopia at 85 years of age. The major causes of visual impairment in highly hyperopic persons were age-related macular degeneration (AMD), cataract, and combined causes (each 25%); in highly myopic persons, the major cause was myopic macular degeneration (38.9%). The major causes of visual impairment for the other refractive error categories were AMD and cataract. Compared with those with emmetropia, those with high myopia had a significantly increased lifetime risk of visual impairment; those with -6 diopters (D) or less and -10 D or more had an odds ratio (OR) risk of 3.4 (95% confidence interval [CI], 1.4-8.2) of visual impairment; those with less than -10 D had an OR of 22.0 (95% CI, 9.2-52.6).

Conclusions: Of all refractive errors, high myopia has the most severe visual consequences. Irreversible macular pathologic features are the most common cause of visual impairment in this group.