title: Prevalence and causes of reduced visual acuity among children aged three to six years in a metropolis in China.
abstract: OBJECTIVE
  To determine the prevalence and possible causes for reduced visual acuity (VA) in preschool children in a metropolis in China.
  
  
  METHODS
  A school-based paediatric eye survey including 5862 preschool children aged three to 6 years was conducted from 2011 to 2012 in Yuhuatai District, Nanjing, China, using an age-stratified random sampling procedure. Clinical examinations including ocular alignment, ocular motility, visual acuity, prism cover test, cycloplegic refraction, stereopsis screening, slit lamp examination and fundus examination were performed by trained study ophthalmologists and optometrists. Reduced VA was defined as presenting VA of worse than 0.30 logMAR (Snellen 6/12 or 20/40), for both better and worse eyes.
  
  
  RESULTS
  5667 (94.8%) children with complete VA data were included in the data analyses. Among them, 208 and 93 had reduced VA in the worse and better eye, respectively. Reduced VA was detected in 3.7% (95% confidence interval [CI] 3.2%-4.2%) in the worse eye and 1.6% (95% CI 1.3%-2.0%) in the better eye. No significant age and gender differences in reduced VA were observed (p > 0.05). Refractive errors and amblyopia were the principal causes for reduced VA in the worse eye which accounted for 66.8% and 32.7% of the total cases with reduced VA, respectively. Astigmatism and hyperopia were the major types of refractive errors causing reduced VA.
  
  
  CONCLUSIONS
  The burden of reduced VA in preschool children in China was similar to that of Asian children of similar ages in the United States. Uncorrected refractive error and amblyopia were the principal causes for reduced VA among preschoolers (aged three to 6 years) in China.
authors.affiliation: Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, School of Public Health, Medical College of Soochow University, Suzhou, China.
authors.forename: Chen-Wei
authors.initials: CW
authors.lastname: Pan
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Xuejuan
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Ophthalmology, Children's Hospital of Soochow University, Suzhou, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Ophthalmology, Wuxi No. 2 People's Hospital, Wuxi, China.
authors.forename: Jiajia
authors.initials: J
authors.lastname: Yu
authors.affiliation: Maternal and Child Healthcare Hospital of Yuhuatai District, Nanjing, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Ding
authors.affiliation: Maternal and Child Healthcare Hospital of Yuhuatai District, Nanjing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Bai
authors.affiliation: Maternal and Child Healthcare Hospital of Yuhuatai District, Nanjing, China.
authors.forename: Ji
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Zhujun
authors.initials: Z
authors.lastname: Fu
authors.affiliation: Department of Ophthalmology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Hu
authors.initials: H
authors.lastname: Liu
mesh_terms: D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D012029:Refraction, Ocular / Q000502:physiology; D012030:Refractive Errors / Q000453:epidemiology / Q000209:etiology / Q000503:physiopathology; D012307:Risk Factors; D014505:Urban Population / Q000706:statistics & numerical data; D014786:Vision Disorders / Q000453:epidemiology / Q000209:etiology / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology
keywords: epidemiology; preschooler; public health; reduced visual acuity