title: Corneal and refractive astigmatism in a sample of 3- to 5-year-old children with a high prevalence of astigmatism.
abstract: OBJECTIVE
  To examine the relation between corneal and refractive astigmatism in a sample of pre-school-age Native American children with a high prevalence of astigmatism.
  
  
  METHODS
  Subjects were 250 Tohono O'Odham children, 3 to 5 years of age. Each child had corneal astigmatism measured with the Marco Nidek KM-500 portable autokeratometer without pupil dilation, and with the Nikon Retinomax K-Plus portable autorefractor/autokeratometer without and with pupil dilation. Refractive astigmatism was measured using the Retinomax K-Plus, with cycloplegia, confirmed by retinoscopy.
  
  
  RESULTS
  Corneal astigmatism exceeded refractive astigmatism, with a median vector dioptric difference of 0.88 D for the KM-500, 0.76 D for the Retinomax K-Plus without dilation, and 0.75 for the Retinomax K-Plus with dilation. The relation between corneal and refractive astigmatism was adequately described by the modification by Grosvenor et al. of Javal's rule, but not by laval's rule.
  
  
  CONCLUSIONS
  The results are in agreement with data reported previously for older Native American and non-Native American populations. The modified laval's rule adequately describes the relation between corneal and refractive astigmatism in a population; however, this rule does not provide accurate prediction of refractive astigmatism in individual children or adults.
authors.affiliation: Department of Ophthalmology, University of Arizona, Tucson 85719-3758, USA. vdobson@eyes.arizona.edu
authors.forename: V
authors.initials: V
authors.lastname: Dobson
authors.forename: J M
authors.initials: JM
authors.lastname: Miller
authors.forename: E M
authors.initials: EM
authors.lastname: Harvey
mesh_terms: D001130:Arizona / Q000453:epidemiology; D001251:Astigmatism / Q000175:diagnosis / Q000208:ethnology*; D002675:Child, Preschool; D003315:Cornea / Q000473:pathology*; D003937:Diagnosis, Differential; D006801:Humans; D007198:Indians, North American; D015995:Prevalence; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology; D012307:Risk Factors