title: The prevalence of anisometropia in population base study.
abstract: OBJECTIVE
  To determine the prevalence of anisometropia and its determinants in the population of Mashhad.
  
  
  METHODS
  In a cross-sectional study in 2008, 4453 residents of Mashhad city between the ages of 1 and 90 years were selected using stratified cluster sampling, of which 70.4% participated in the study. All respondents had visual acuity and refraction testing. Anisometropia was defined as the absolute interocular difference in the spherical equivalent based on non-cycloplegic refraction. The prevalence rates and 95% confidence intervals (CI) of anisometropia were determined based on cut points of 0.5 diopter (D), 1.0 D, and 2.0 D or more, and we used the 1.0 D cut point to examine associations.
  
  
  RESULTS
  After applying exclusion criteria, data from 2947 participants were used in the analyses. Based on cut points of 0.5 D, 1.0 D, and 2.0 D or more, the prevalence of anisometropia was 17.0% (n = 451) (95% CI, 15.1-18.8), 5.6% (n = 148) (95% CI, 4.6-6.6), and 1.7% (n = 50) (95% CI, 1.2-2.2), respectively. The odds of anisometropia showed a significant increase of 2.8% with every year of aging (P < 0.001); 2.6% and 2.8% were anisomyopic and anisohyperopic, respectively. The prevalence of anisometropia was directly associated with myopia (P < 0.001) as well as a history of ocular trauma (P < 0.001). The prevalence of anisoastigmatism was 5.6% and significantly increased with age (P < 0.001).
  
  
  CONCLUSIONS
  The prevalence of anisometropia in the studied population, compared to studies conducted in the Middle Eastern Region and East Asia, is in the midrange. The prevalence of anisometropia is higher at older age, however, children should receive more attention due to the risk of amblyopia. A history of ocular trauma is a risk factor for anisometropia.
authors.affiliation: Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Hadi
authors.initials: H
authors.lastname: Ostadimoghaddam
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Abbas Ali
authors.initials: AA
authors.lastname: Yekta
authors.forename: Javad
authors.initials: J
authors.lastname: Heravian
authors.forename: Bahareh
authors.initials: B
authors.lastname: Hemmati
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Jafarzadehpur
authors.forename: Farhad
authors.initials: F
authors.lastname: Rezvan
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D015858:Anisometropia / Q000453:epidemiology / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D015995:Prevalence; D012029:Refraction, Ocular; D012189:Retrospective Studies; D012307:Risk Factors; D017678:Sex Distribution; D055815:Young Adult