To assess the prevalence and risk factors of undercorrected refractive error in South Korea.

We analyzed 36,162 participants for estimating prevalence using the Korean National Health and Nutrition Examination Survey (KNHANES, 2008-2012). Undercorrected refractive error was defined as an improvement of at least 2 lines in best corrected visual acuity compared with the presenting visual acuity in the right eye. Proportion of undercorrected refractive error by occupation was presented, and associated sociodemographic factors were evaluated by multivariable logistic regression.

The prevalence of undercorrected refractive error among all participants and among adults was 8.5% (n/N, 6,954/36,162) and 18.8% (n/N, 3,980/19,884), respectively. The proportion of undercorrected refractive error was higher among those with did not wear spectacles or contact lenses (23.1%) than among spectacle or contact lens wearers (8.1%). The proportion of participants who gained more than four or more lines of best corrected visual acuity was 7.2% (n = 2,606) for the all age group. In terms of occupation, farming, fishing, and forestry occupations (22.8%, 570/2,499) and laborer (20.2%, 497/2,457) were more likely to have undercorrected refractive error. Age groups of 10s, 70s, or 80s (30s as a reference group), female sex, lower income, lower education level, and living without a spouse were associated with undercorrected refractive error.

People of older age, female sex, and lower socioeconomic status were more likely to have undercorrected refractive error. This suggests that a public-health approach is needed for preventing visual impairment via proper vision correction.