Ametropia prevalence of primary school students in Chinese multi-ethnic regions.

: To explore the prevalence of visual impairment due to uncorrected ametropia from primary students in multi-ethnic regions of Yunnan (Southern China).: Primary school students of 7 ~ 12 years old from 5 multi-ethnic regions were screened. Cycloplegic refraction and subjective trial lens visual acuity were measured in all children with distance unaided visual acuity < 20/20. Gender, ages, ethnics, and regions were assessed with analysis of difference and Odds Ratio (OR) respectively, by statistics software R.: Of all 24296 children, the incidence rate for visual impairment from ametropia was 19.18% (myopia accounted for 94.31%) for 7 ~ 12 years old in Yunnan primary schools in a multi-ethnic region. Myopia prevalence differed significantly among gender, ages, ethnics, and regions (P = .0003, P < .00001, P < .00001, P < .00001, respectively). Girls were more prone to have myopia (OR = 1.19, 95%, CI = 1.11-1.27) than boys; the risk of myopia increased with age: 9-10 years OR = 2.6 (95% CI = 2.62-3.2), 11-12 years OR = 6.6 (95% CI = 6-7.26). Three ethnic minorities surveyed were less prone to myopia than Han: Dai OR = 0.62 (95% CI = 0.47-0.8) Hani OR = 0.56 (95%CI = 0.41-0.76) Buyi OR = 0.50 (95% CI = 0.4-0.62).: Myopia, not corrected by glasses, was the most frequent cause of visual impairment in Yunnan primary schools, in a muli-ethnic region. Boys, young children and certain ethnic minorities were less prone to myopia.