Background <p>Ambient air pollution may contribute to the growing burden of myopia, but evidence from large population-based studies remains limited. We evaluated the association between long-term exposure to ambient air pollution and the prevalence and severity of myopia in young Korean men.</p> Methods <p>We analyzed nationwide military conscription examination data from 2010 to 2020, including 1,671,826 nineteen-year-old men residing in seven metropolitan cities. Participants without educational attainment data or living outside major urban areas were excluded. We examined the association between district-level 3-year average concentrations of particulate matter (PM₂.₅ and PM₁₀) and nitrogen dioxide (NO₂) with the prevalence and severity of myopia using logistic regression models adjusted for individual and district-level covariates. Sensitivity analyses considered 1- and 6-year exposure averages.</p> Results <p>Higher NO₂ exposure was associated with increased odds of myopia (OR per IQR: 1.262; 95% CI: 1.254–1.270), with stronger associations for high myopia (OR per IQR: 1.354; 95% CI: 1.342–1.366), in models adjusted for individual-level covariates. A clear dose-response pattern was observed across NO₂ quartiles. PM₁₀ also showed positive but weaker and less consistent associations, with slightly stronger links to low myopia. In contrast, PM₂.₅ demonstrated consistent inverse associations, likely reflecting temporal confounding due to limited data availability. Sensitivity analyses yielded similar results.</p> Conclusions <p>Long-term exposure to NO₂ and PM₁₀ may contribute to both the development and progression of myopia, with NO₂ showing particularly strong associations for high myopia. Further longitudinal studies are warranted to clarify these relationships and inform preventive strategies.</p>