Prevalence of Refractive Errors in the Elderly Population of Yazd District, Iran

To determine prevalence and associated factors of refractive errors in elderly population of Yazd, Iran. This is a cross-sectional population-based survey performed between 2010 and 2011. The participants were among the subjects aged from 40 to 80 years old. The samples were selected from urban and rural inhabitants using multi-stage random cluster sampling design. All participants underwent manifest refraction, visual acuity measurements, retinoscopy and funduscopy. Myopia, hyperopia, astigmatism and anisometropia were defined as, spherical equivalent (SE) > -0.50 D, > 0.50 D, cylinder power > 0.5 D, as well as a difference of 1 D or higher in SE of the right and left eyes, respectively. Of 2320 individuals selected, 2098 (90.4%) subjects participated in the study. out of which, 198 subjects were excluded due to previous surgical history. Prevalence of myopia, hyperopia, astigmatism, and anisometropia were 36.5% (95% confidence interval [95% CI]; 33.6-39.4%), 20.6% 95% CI; 17.9-23.3%), 53.8% (95% CI; 51.3-56.3%), 11.9% (95% CI; 10.4-13.4%), respectively. Myopia ≥ -6 D and hyperopia ≥ +4 D were observed in 2.3% (95% CI; 1.6-2.9%) and 1.2% (95% CI; 0.6-1.8%)of participants, respectively. Multiple logistic regression model shows that myopia prevalence significantly increased in female subjects. In addition, the prevalence of hyperopia, astigmatism, and anisometropia directly correlated with age. With-therule, against-the-rule and oblique astigmatisms prevalence were 35.7%, 13.4% and 4.6%, respectively; prevalence of against-the-rule astigmatism increased from 27.6% among 40-49 year-old subjects to 55.2% among 70-80 year-old subjects (OR=1.044, 95%CI, 1.034-1.054, P<0.001). With-the rule astigmatism prevalence was significantly higher in women (P=0.038). More than half of the study population had at least one refractive error; myopia and astigmatism prevalence were found to be considerably higher compared to previous studies in Iran. As the refractive errors are a main cause of avoidable visual impairment, high prevalence of refractive errors in this study is important from a public health perspective.