Analysis of Risk Factor Changes for Myopia in Korean Adolescents Before and After the COVID-19 Pandemic

Background and Objectives: To analyze changes in risk factors for refractive errors among Korean adolescents before and after the COVID-19 pandemic and examine the impact of lifestyle modifications on myopia development, Methods: this cross-sectional study utilized nationally representative data from the Korea National Health and Nutrition Examination Survey (KNHANES) VII (2016) and VIII (2021). We analyzed 691 adolescents aged 10–18 years from 2016 (pre-COVID-19) and 490 from 2021 (post-COVID-19). Refractive errors were categorized as hyperopia (≥+0.50 D), emmetropia (−0.50 to +0.50 D), myopia (−6.00 to −0.50 D), and high myopia (≤−6.00 D). Complex sample linear regression analyses identified factors associated with spherical equivalent (SE) refractive errors. Results: At the population level, overall myopia prevalence declined from 84.2% in 2016 to 77.4% in 2021, whereas the prevalence of high myopia increased from 10.0% to 11.5% (p = 0.047). This indicates that although the absolute proportion of adolescents with myopia decreased, the relative contribution of high myopia to the overall myopia burden within this population increased. Mean SE was −2.77 ± 0.11 D in (−10.63~+3.00 D/median: −2.00 D) 2016 and −2.63 ± 0.13 D (−14.00~+1.63/median: −1.75 D) in 2021 (p = 0.443). Age-related myopia progression accelerated post-pandemic (−0.193 D to −0.324 D per year in univariate regression and −0.185 D to −0.312 D, in multivariate regression analysis, p < 0.001). In both the 3 h and ≥4 h near work groups, statistically significant associations were observed at both time points, but a greater myopic shift was evident after COVID-19 (B = –0.853 and –0.757 in 2016; B = –1.311 and –1.167 in 2021, p < 0.05). Conclusions: The COVID-19 pandemic altered myopia risk factors among Korean adolescents. High myopia prevalence increased despite overall myopia with underweight status and environmental factors such as digital device time and urban living identified as important considerations for post-pandemic myopia prevention.