title: Development of phoria in children.
abstract: BACKGROUND
  Although the prevalence of phoria in adults is well documented, data are scarce on phoria in children. We present results using modified clinical technique vision screening and data from the Orinda Longitudinal Study of Myopia on a large, population-based sample of nonstrabismic children to document the prevalence of phoria with age.
  
  
  METHODS
  We collected cross-sectional (N = 1495) and longitudinal (N = 469) data. Phoria data were collected by cover tests administered by one observer who subjectively classified phoria as orthophoria, esophoria, or exophoria in 2 delta steps.
  
  
  RESULTS
  Ninety-seven percent of the children were orthophoric at distance, and there were no significant changes with age. Near phoria showed a more normal distribution, with a 10.8% decrease in the prevalence of exophoria (from 31.8 to 21.0%) and a 5.5% increase in the prevalence of esophoria (from 6.7 to 12.2%) between kindergarten and fifth grade.
  
  
  CONCLUSIONS
  Children are typically orthophoric or exophoric at near, but convergent shifts occur with age.
authors.affiliation: The Ohio State University College of Optometry, Columbus 43210-1240, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Walline
authors.forename: D O
authors.initials: DO
authors.lastname: Mutti
authors.forename: K
authors.initials: K
authors.lastname: Zadnik
authors.forename: L A
authors.initials: LA
authors.lastname: Jones
mesh_terms: D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D006801:Humans; D015995:Prevalence; D012030:Refractive Errors / Q000175:diagnosis / Q000503:physiopathology; D013285:Strabismus / Q000175:diagnosis* / Q000503:physiopathology; D015351:Vision Screening / Q000379:methods