title: Prevalence and risk factors for visual impairment in preschool children the sydney paediatric eye disease study.
abstract: OBJECTIVE
  To assess the prevalence and associations of visual impairment (VI) in preschool children.
  
  
  METHODS
  Cross-sectional, population-based study.
  
  
  METHODS
  A total of 2461 children (73.8% participation rate), aged 6 to 72 months, were examined in the Sydney Paediatric Eye Disease Study during 2007-2009; of whom 1188, aged 30 to 72 months, with complete visual acuity (VA) data in both eyes, were included in this report.
  
  
  METHODS
  Measurement of VA was attempted on all children using the Electronic Visual Acuity (EVA) system or a logarithm of the minimum angle of resolution (logMAR) chart. Visual impairment was defined as presenting VA <20/40 in children aged ≥48 months and <20/50 in those aged <48 months. Post-cycloplegic refraction was measured, and myopia was defined as spherical equivalent (SE) ≤-0.50 diopters (D), hyperopia was defined as SE ≥2.00 D, astigmatism was defined as cylinder ≥1.00 D, and anisometropia was defined as SE difference ≥1.00 D between 2 eyes. Ethnicity, birth parameters, and sociodemographic information were collected in questionnaires completed by parents.
  
  
  METHODS
  Visual impairment prevalence and its associations with child demographic factors and birth parameters.
  
  
  RESULTS
  Visual impairment was found in 6.4% of the worse eye and 2.7% of the better eye in our sample. Refractive errors (69.7%) and amblyopia (26.3%) were the principal causes of VI in the worse eye. Astigmatism (51.3%) and hyperopia (28.9%) were the main refractive errors causing VI. In regression analysis controlling for other factors, VI was independently associated with low birthweight of <2500 g (odds ratio 2.4, 95% confidence interval, 1.1-5.3), but not with age, gender, ethnicity, or measures of socioeconomic status (P > 0.05).
  
  
  CONCLUSIONS
  Visual impairment in at least 1 eye was found in 6.4% of Australian preschool children, with bilateral VI found in 2.7%. Uncorrected refractive errors and amblyopia were the principal ocular conditions associated with VI. Low birthweight was a significant risk factor independent of age, gender, and ethnicity.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Centre for Vision Research, Westmead Millennium Institute (Westmead Hospital), University of Sydney, Sydney, Australia.
authors.forename: Amy Shih-I
authors.initials: AS
authors.lastname: Pai
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
authors.forename: Chameen
authors.initials: C
authors.lastname: Samarawickrama
authors.forename: George
authors.initials: G
authors.lastname: Burlutsky
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Rose
authors.forename: Rohit
authors.initials: R
authors.lastname: Varma
authors.forename: Tien Yin
authors.initials: TY
authors.lastname: Wong
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
mesh_terms: D001724:Birth Weight; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005006:Ethnicity; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009517:New South Wales / Q000453:epidemiology; D015995:Prevalence; D012029:Refraction, Ocular / Q000502:physiology; D012030:Refractive Errors / Q000208:ethnology*; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014786:Vision Disorders / Q000208:ethnology*; D014792:Visual Acuity / Q000502:physiology; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*