title: Retrospective analysis of refractive errors in children with vision impairment.
abstract: OBJECTIVE
  Emmetropization is the reduction in neonatal refractive errors that occurs after birth. Ocular disease may affect this process. We aimed to determine the relative frequency of ocular conditions causing vision impairment in the pediatric population and characterize the refractive anomalies present. We also compared the causes of vision impairment in children today to those between 1974 and 1981.
  
  
  METHODS
  Causes of vision impairment and refractive data of 872 children attending a pediatric low-vision clinic from 1985 to 2002 were retrospectively collated. As a result of associated impairments, refractive data were not available for 59 children. An analysis was made of the causes of vision impairment, the distribution of refractive errors in children with vision impairment, and the average type of refractive error for the most commonly seen conditions.
  
  
  RESULTS
  We found that cortical or cerebral vision impairment (CVI) was the most common condition causing vision impairment, accounting for 27.6% of cases. This was followed by albinism (10.6%), retinopathy of prematurity (ROP; 7.0%), optic atrophy (6.2%), and optic nerve hypoplasia (5.3%). Vision impairment was associated with ametropia; fewer than 25% of the children had refractive errors < or = +/-1 D. The refractive error frequency plots (for 0 to 2-, 6 to 8-, and 12 to 14-year age bands) had a Gaussian distribution indicating that the emmetropization process was abnormal. The mean spherical equivalent refractive error of the children (n = 813) was +0.78 +/- 6.00 D with 0.94 +/- 1.24 D of astigmatism and 0.92 +/- 2.15 D of anisometropia. Most conditions causing vision impairment such as albinism were associated with low amounts of hyperopia. Moderate myopia was observed in children with ROP.
  
  
  CONCLUSIONS
  The relative frequency of ocular conditions causing vision impairment in children has changed since the 1970s. Children with vision impairment often have an associated ametropia suggesting that the emmetropization system is also impaired.
authors.affiliation: Centre for Health Research-Optometry, Queensland University of Technology, Victoria Park Road, Kelvin Grove 4059, Brisbane, Queensland, Australia.
authors.forename: Jojo W
authors.initials: JW
authors.lastname: Du
authors.forename: Katrina L
authors.initials: KL
authors.lastname: Schmid
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Bevan
authors.forename: Karen M
authors.initials: KM
authors.lastname: Frater
authors.forename: Rhondelle
authors.initials: R
authors.lastname: Ollett
authors.forename: Bronwyn
authors.initials: B
authors.lastname: Hein
mesh_terms: D000293:Adolescent; D005260:Female; D006801:Humans; D008297:Male; D011793:Queensland / Q000453:epidemiology; D012030:Refractive Errors / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*