Anisometropia in population base study: The Mashhad Eye Study

AbstractPurpose 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 was determined based on cutpoints of 0.5 diopter (D), 1.0 D, and 2.0 D or more, and we used the 1.0D cutpoint to examine associations.Results After applying exclusion criteria, data from 2947 participants were used in the analyses. Based on cutpoints of 0.5D, 1.0D, and 2.0 D or more, the prevalence of anisometropia was 17.0% (95% CI, 15.1‐18.8), 5.6% (95% CI, 4.6‐6.6), and 1.7% (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).Conclusion 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.