title: A population-based study of visual impairment among pre-school children in Beijing: the Beijing study of visual impairment in children.
abstract: OBJECTIVE
  To evaluate the prevalence and causes of visual impairment among Chinese children aged 3 to 6 years in Beijing.
  
  
  METHODS
  Population-based prevalence survey.
  
  
  METHODS
  Presenting and pinhole visual acuity were tested using picture optotypes or, in children with pinhole vision < 6/18, a Snellen tumbling E chart. Comprehensive eye examinations and cycloplegic refraction were carried out for children with pinhole vision < 6/18 in the better-seeing eye.
  
  
  RESULTS
  All examinations were completed on 17,699 children aged 3 to 6 years (95.3% of sample). Subjects with bilateral correctable low vision (presenting vision < 6/18 correctable to >or= 6/18) numbered 57 (0.322%; 95% confidence interval [CI], 0.237% to 0.403%), while 14 (0.079%; 95% CI, 0.038% to 0.120%) had bilateral uncorrectable low vision (best-corrected vision of < 6/18 and >or= 3/60), and 5 subjects (0.028%; 95% CI, 0.004% to 0.054%) were bilaterally blind (best-corrected acuity < 3/60). The etiology of 76 cases of visual impairment included: refractive error in 57 children (75%), hereditary factors (microphthalmos, congenital cataract, congenital motor nystagmus, albinism, and optic nerve disease) in 13 children (17.1 %), amblyopia in 3 children (3.95%), and cortical blindness in 1 child (1.3%). The cause of visual impairment could not be established in 2 (2.63%) children. The prevalence of visual impairment did not differ by gender, but correctable low vision was significantly (P < .0001) more common among urban as compared with rural children.
  
  
  CONCLUSIONS
  The leading causes of visual impairment among Chinese preschool-aged children are refractive error and hereditary eye diseases. A higher prevalence of refractive error is already present among urban as compared with rural children in this preschool population.
authors.affiliation: Shenyang He Eye Hospital, Shenyang, China. lulq@hotmail.com
authors.forename: Qing
authors.initials: Q
authors.lastname: Lu
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zheng
authors.forename: Baochen
authors.initials: B
authors.lastname: Sun
authors.forename: Tongtong
authors.initials: T
authors.lastname: Cui
authors.forename: Nathan
authors.initials: N
authors.lastname: Congdon
authors.forename: Ailian
authors.initials: A
authors.lastname: Hu
authors.forename: Jianhua
authors.initials: J
authors.lastname: Chen
authors.forename: Jiliang
authors.initials: J
authors.lastname: Shi
mesh_terms: D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D015785:Eye Diseases, Hereditary / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D015995:Prevalence; D012030:Refractive Errors / Q000453:epidemiology; D012424:Rural Population / Q000706:statistics & numerical data; D014505:Urban Population / Q000706:statistics & numerical data; D014786:Vision Disorders / Q000453:epidemiology*; D014787:Vision Tests; D014792:Visual Acuity; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*