title: PowerRefractor versus Canon R-50 Autorefraction to assess refractive error in children: a community-based study in ecuador.
abstract: OBJECTIVE
  To compare the agreement of the PowerRefractor with Canon R-50 autorefraction for measuring refractive error in a community of Ecuadorian children.
  
  
  METHODS
  We examined 1564 children aged 5 to 6 years from two ethnically and geographically similar regions of the Ecuadorian highlands. Results of a refraction obtained without cycloplegia with the PowerRefractor and with the Canon R-50 autorefractor (NCAR) were compared with the gold-standard examination, cycloplegic autorefraction (CAR) with the Canon R-50 autorefractor. Power vectors were used to analyze refractive error. Bland-Altman limits of agreement were obtained.
  
  
  RESULTS
  Although the mean difference in the spherical equivalent refractive error between the PowerRefractor and CAR was small (-0.03 D +/- 0.05 D), the 95% limits of agreement were wide (+/-2.03 D). On the other hand, NCAR showed a greater bias (0.97 D +/- 0.04 D) and smaller limits of agreement (+/-1.49 D). The limits of agreement of the PowerRefractor were also wider than NCAR for measuring astigmatism. When the mean difference was stratified by the subgroups of refractive error vectors, the PowerRefractor was found to have poorer limits of agreement than NCAR for hyperopic defects.
  
  
  CONCLUSIONS
  The PowerRefractor is accurate, but not as precise for measuring refractive error as compared to the Canon R-50 autorefractor, especially for high hyperopia.
authors.affiliation: Department of Oto-Neuro-Ophthalmological Surgical Sciences, University of Florence, Florence, Italy. gianni.virgili@unifi.it
authors.forename: Gianni
authors.initials: G
authors.lastname: Virgili
authors.forename: Mario
authors.initials: M
authors.lastname: Angi
authors.forename: Santa
authors.initials: S
authors.lastname: Heede
authors.forename: Diana
authors.initials: D
authors.lastname: Rodriguez
authors.forename: Elisa
authors.initials: E
authors.lastname: Bottega
authors.forename: Andrea
authors.initials: A
authors.lastname: Molinari
mesh_terms: D002648:Child; D002675:Child, Preschool; D004484:Ecuador / Q000453:epidemiology; D004867:Equipment Design; D006801:Humans; D015994:Incidence; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000175:diagnosis* / Q000453:epidemiology*; D012031:Refractometry / Q000295:instrumentation*; D012720:Severity of Illness Index