title: Anisometropia is independently associated with both spherical and cylindrical ametropia.
abstract: OBJECTIVE
  To explore the associations between anisometropia and spherical ametropia, astigmatism, age, and sex.
  
  
  METHODS
  Associations between the prevalence and magnitude of anisometropia with age, sex, spherical power, and cylindrical power, were assessed in a group of 90,884 subjects attending optometry practices in the United Kingdom. Logistic regression models were used to assess the independent contribution of each explanatory variable.
  
  
  RESULTS
  Logistic regression analyses that included all subjects or just those aged 20 to 40 years showed that spherical ametropia and astigmatism were independently associated with anisometropia (myopes, P < 1.0E-61; hyperopes, P < 1.0E-11). Anisometropia was relatively stable between the ages of 20 and 40 years, but then became more common with age, in myopes from the age of 40 years onward (P < 0.003) and in hyperopes from the age of 70 years onward (P < 1.0E-6). Sex was not associated with anisometropia to a clinically significant extent.
  
  
  CONCLUSIONS
  This is the first study to show an independent association between anisometropia and both spherical ametropia and astigmatism. The results also suggest that the previously noted increased prevalence of anisometropia with age occurs later in hyperopes than in myopes, once other covariates have been controlled for. However, it could not be ruled out that this latter effect was due to clinical selection bias in our sample. The findings suggest that research projects involving the recruitment of highly ametropic subjects, such as those investigating the genetics of refractive error, may benefit by avoiding the use of stringent inclusion criteria for anisometropia, because otherwise a large proportion of the relevant population will be excluded.
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, Wales, UK.
authors.forename: Xue-Jiao
authors.initials: XJ
authors.lastname: Qin
authors.forename: Tom H
authors.initials: TH
authors.lastname: Margrain
authors.forename: Chi Ho
authors.initials: CH
authors.lastname: To
authors.forename: Nathan
authors.initials: N
authors.lastname: Bromham
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Guggenheim
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015858:Anisometropia / Q000150:complications / Q000453:epidemiology*; D001251:Astigmatism / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012030:Refractive Errors / Q000150:complications / Q000453:epidemiology*; D012737:Sex Factors; D006113:United Kingdom / Q000453:epidemiology