title: Prevalence and risk factors for anisometropia in the Tehran eye study, Iran.
abstract: OBJECTIVE
  To determine the prevalence of anisometropia and its determinants in a population-based sample.
  
  
  METHODS
  In a cross-sectional population-based study, stratified cluster sampling was carried out from the population of Tehran. Respondents were transferred to a clinic for an interview and ophthalmic examinations including tests for visual acuity with and without correction, cycloplegic refraction, the slit lamp examination, fundoscopy, and lensometry. Anisometropia was defined as unequal spherical equivalent cycloplegic refractions in the two eyes.
  
  
  RESULTS
  Of 4565 participants, cycloplegic refraction was performed in both eyes of 3519 people. The mean age of the examinees was 31.5 ± 18.0 (range, 5-86) years. The mean anisometropia was 0.34 diopter (D) (95% Confidence Interval (CI): 0.31-0.37). The prevalence rates of anisometropia more than 0.5, 1.0, 1.5 and 2.0 D were 18.5% (95% CI: 17.0-19.9), 6.7% (95% CI: 5.8-7.7), 3.8% (95% CI: 3.1-4.5) and 2.6% (95% CI: 2.1-3.1). The inter-gender difference in the prevalence of anisometropia ≥ 1.0D was not statistically significant (P = 0.952). The prevalence of anisometropia increased after the age of 45 years. Overall, 15.7% of the examinees had anisomyopia and 4.7% had anisohypermetropia equal to or more than 1.0D. Anisometropia was more prevalent among patients with cataracts, amblyopia, and pseudophakia. The prevalence rates of spherical and cylindrical anisometropia in the studied sample were 8.0% and 7.1%, respectively.
  
  
  CONCLUSIONS
  The prevalence of anisometropia in the population of Tehran is beyond negligible. It showed a significant increase with age. Results also indicate that myopic patients are more likely to have anisometropia.
authors: Farabi Eye Hospital, Tehran University of Medical Sciences, Iran.
authors: Hassan
authors: H
authors: Hashemi
authors: Mehdi
authors: M
authors: Khabazkhoob
authors: Abbasali
authors: A
authors: Yekta
authors: Kazem
authors: K
authors: Mohammad
authors: Akbar
authors: A
authors: Fotouhi