RESUMEN
BACKGROUND: To calculate and evaluate the prevalence of reduced uncorrected distant visual acuity (UCDVA) in primary, middle and high schools in 6 districts of Changsha, Hunan, China. METHODS: A population-based retrospective study was conducted in 239 schools in 6 districts of Changsha. After routine eye examination to rule out diseases that can affect refraction, 250,980 eligible students from primary, middle and high schools were enrolled in the survey. Then the uncorrected distant and near visual acuity of each eye were measured. Categories of schools, districts, grades, eye exercises and sports time were also documented and analyzed. RESULTS: The overall prevalence of reduced UCDVA was 51.8% (95% confidence interval [CI]: 51.6-52.0%) in 6 districts of Changsha. Results of individual districts were as follows: Furong district 59.9%(95% CI: 57.9-61.8%), Tianxin district 62.3%(95% CI: 60.5-64.0%), Wangcheng district 47.8%(95% CI: 46.8-48.8%), Kaifu district 58.5%(95% CI: 58.0-58.9%), Yuhua district 47.0%(95% CI: 46.7-47.4%) and Yuelu district 52.6%(95% CI: 52.3-52.9%). The proportion of normal VA is seen to decrease from primary grade 3. The proportion of mildly reduced UCDVA is higher in primary grade 1 and 2. The proportion of moderately reduced UCDVA remains similar during 12 grades. The proportion of severely reduced UCDVA increases with grades. Multivariate analysis shows that the prevalence of reduced UCDVA is higher in key schools (risk ratio [RR] = 1.47, 95% CI 1.44-1.50) than non-key schools. CONCLUSIONS: According to the existing data analysis results, the prevalence of reduced UCDVA among primary, middle and high school students in Changsha is very high. Some effective measures need to be taken to prevent it.