Refractive Error, Visual Acuity and Causes of Vision Loss in Children in Shandong, China. The Shandong Children Eye Study

PURPOSE To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China. METHODS Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergartens, primary schools, and junior and senior high schools in the rural Guanxian County and the city of Weihai. All children underwent a complete ocular examination including measurement of uncorrected (UCVA) and best corrected visual acuity (BCVA) and auto-refractometry under cycloplegia. Myopia was defined as refractive error of ≤-0.5 diopters (D), high myopia as ≤ -6.0D, and amblyopia as BCVA ≤ 20/32 without any obvious reason for vision reduction and with strabismus or refractive errors as potential reasons. RESULTS Out of 6364 eligible children, 6026 (94.7%) children participated. Prevalence of myopia (overall: 36.9 ± 0.6%;95% confidence interval (CI):36.0,38.0) increased (P<0.001) from 1.7 ± 1.2% (95%CI:0.0,4.0) in the 4-years olds to 84.6 ± 3.2% (95%CI:78.0,91.0) in 17-years olds. Myopia was associated with older age (OR:1.56;95%CI:1.52,1.60;P<0.001), female gender (OR:1.22;95%CI:1.08,1.39;P = 0.002) and urban region (OR:2.88;95%CI:2.53,3.29;P<0.001). Prevalence of high myopia (2.0 ± 0.2%) increased from 0.7 ± 0.3% (95%CI:0.1,1.3) in 10-years olds to 13.9 ± 3.0 (95%CI:7.8,19.9) in 17-years olds. It was associated with older age (OR:1.50;95%CI:1.41,1.60;P<0.001) and urban region (OR:3.11;95%CI:2.08,4.66);P<0.001). Astigmatism (≥ 0.75D) (36.3 ± 0.6%;95%CI:35.0,38.0) was associated with older age (P<0.001;OR:1.06;95%CI:1.04,1.09), more myopic refractive error (P<0.001;OR:0.94;95%CI:0.91,0.97) and urban region (P<0.001;OR:1.47;95%CI:1.31,1.64). BCVA was ≤ 20/40 in the better eye in 19 (0.32%) children. UCVA ≤ 20/40 in at least one eye was found in 2046 (34.05%) children, with undercorrected refractive error as cause in 1975 (32.9%) children. Amblyopia (BCVA ≤ 20/32) was detected in 44 (0.7%) children (11 children with bilateral amblyopia). CONCLUSIONS In coastal East China, about 14% of the 17-years olds were highly myopic, and 80% were myopic. Prevalence of myopia increased with older age, female gender and urban region. About 0.7% of pre-school children and school children were amblyopic.