Screening-based prevalence and axis distribution of astigmatism among children and adolescents in Lintong District, Xi'an: a large-scale school-based cross-sectional study.

BACKGROUND

District-level information on childhood astigmatism is useful for school vision screening, but estimates vary according to population structure, astigmatism definition, and refraction protocol. We described screening-based astigmatism prevalence, severity, and axis distribution among schoolchildren in Lintong District, Xi'an.

METHODS

This cross-sectional study used a district-wide school vision screening database collected from September to November 2023. Among 65,843 screened students aged 7-19 years, 65,127 were included after exclusions. Non-cycloplegic autorefraction was performed using the Topcon KR-8800 autorefractor (Topcon Corporation, Tokyo, Japan). Astigmatism was defined as cylinder power <= -0.75 D in minus-cylinder notation and classified as low, moderate, or high. Refractive status was classified using spherical equivalent; because spherical equivalent includes cylinder power, refractive-status subgroup analyses were interpreted as coexistence patterns rather than independent causal effects. Right-eye data were analyzed. Descriptive comparisons were used as the primary analyses, and multivariable regression results were retained as supplementary descriptive analyses.

RESULTS

Overall astigmatism prevalence was 36.72%, and high astigmatism prevalence was 1.85% (1,202 students). Prevalence was 28.70% in primary school, 44.69% in junior middle school, and 52.41% in senior high school. With-the-rule astigmatism predominated among astigmatic students (89.71%). Myopic students had higher astigmatism prevalence and a higher proportion of moderate-to-high astigmatism than emmetropic students; this finding should be interpreted cautiously because of mathematical coupling between spherical equivalent and cylinder.

CONCLUSIONS

Astigmatism was common in this large district school screening dataset and differed by school stage, axis type, and refractive-status category. The findings may help local screening programs plan re-examination and referral pathways, but they should not be interpreted as cycloplegic clinical diagnoses or as evidence of temporal progression or causality.