Global Patterns of Myopia, Age, Sex, and Vision Loss: A Comparative Analysis of US and South Korean National Surveys.

Objective: Myopia prevalence is rising globally and has reached critical levels in some regions. Beyond refractive correction needs, myopia is a major risk factor for irreversible, vision-threatening ocular disease. This study investigated the relationship between myopia, age, sex, and visual impairment in 2 nationally representative populations in the United States and South Korea. Design: A cross-sectional analysis using data from the US National Health and Nutrition Examination Survey (NHANES) and the Korean National Health and Nutrition Examination Survey (KNHANES). Participants: Participants in the NHANES and KNHANES. Methods: Best-corrected visual acuity (BCVA) and noncycloplegic refractive error were analyzed from NHANES (1999-2008) and KNHANES (2008-2022), excluding those with cataract or refractive surgery. Visual impairment was defined as BCVA ≥0.30 logarithm of the minimum angle of resolution. Logistic regression and Kaplan-Meier analyses were used to evaluate and visualize the cumulative risk of visual impairment by refractive error age and sex. Main Outcome Measures: Visual impairment probability and the odds ratios (ORs) for visual impairment by region, age, and degree of myopia. Results: Visual impairment rates increased with both myopia severity and age in both populations. Among younger nonmyopes, impairment affected 1%, rising to 50% in high myopes by age 75. High myopes had up to 13-fold higher odds of visual impairment than nonmyopes. Age-related risks were similar across regions, but myopia had a stronger effect in South Korea: each 1 D increase in myopia raised the odds of impairment by 41% versus 27% in the United States. Sex was not a significant factor in the United States ( Conclusions: Myopia substantially increases the risk of visual impairment in both the United States and South Korea, with risk rising proportionally with myopia severity. Age-related effects were similar across cohorts, though myopia exerted a greater influence in South Korea. Females demonstrated higher rates of visual impairment independently of refractive error. These findings highlight myopia as a global health concern, reinforcing the need for prevention and early intervention to reduce lifetime risk across all severities. Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.