title: Refractive error, visual acuity and causes of vision loss in children in Shandong, China. The Shandong Children Eye Study.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Ophthalmology, Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China.
authors.forename: Jian Feng
authors.initials: JF
authors.lastname: Wu
authors.affiliation: Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China.
authors.forename: Hong Sheng
authors.initials: HS
authors.lastname: Bi
authors.affiliation: School of Public Health, Shandong University, Jinan, Shandong, China.
authors.forename: Shu Mei
authors.initials: SM
authors.lastname: Wang
authors.affiliation: The Second Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China.
authors.forename: Yuan Yuan
authors.initials: YY
authors.lastname: Hu
authors.affiliation: Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
authors.affiliation: The Second Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.affiliation: The Second Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China.
authors.forename: Tai Liang
authors.initials: TL
authors.lastname: Lu
authors.affiliation: Eye Institute of Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China.
authors.forename: Xing Rong
authors.initials: XR
authors.lastname: Wang
authors.affiliation: Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karls-University, Heidelberg, Germany.
authors.forename: Jost B
authors.initials: JB
authors.lastname: Jonas
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D001766:Blindness / Q000453:epidemiology / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D012030:Refractive Errors / Q000150:complications* / Q000453:epidemiology* / Q000503:physiopathology; D014792:Visual Acuity