title: Prevalence of refractive errors; the yazd eye study.
abstract: OBJECTIVE
  To determine the prevalence of refractive errors in Yazd, central Iran.
  
  
  METHODS
  This population-based study was performed in 2010-2011 and targeted adults aged 40 to 80 years. Multi-stage random cluster sampling was applied to select samples from urban and rural residents of Yazd. Manifest refraction, visual acuity measurement, retinoscopy and funduscopy were performed for all subjects. Myopia, hyperopia, astigmatism and anisometropia were defined as spherical equivalent (SE) <-0.50 diopters (D), SE >+0.50 D, cylindrical error >0.5 D and SE difference ≥1 D between fellow eyes, respectively.
  
  
  RESULTS
  From a total of 2,320 selected individuals, 2,098 subjects (90.4%) participated out of which 198 subjects were excluded due to previous eye surgery. The prevalence (95% confidence interval) for myopia, hyperopia, astigmatism, anisometropia, -6 D myopia or worse, and 4 D hyperopia or worse was 36.5% (33.6-39.4%), 20.6% (17.9-23.3%), 53.8% (51.3-56.3%), 11.9% (10.4-13.4%), 2.3% (1.6-2.9%) and 1.2% (0.6-1.8%), respectively. The prevalence of hyperopia, astigmatism and anisometropia increased with age. The prevalence of myopia was significantly higher in female subjects. The prevalence of with-the-rule, against-the-rule and oblique astigmatism was 35.7%, 13.4% and 4.6%, respectively. The prevalence of against-the-rule astigmatism increased with age (P<0.001); with-the-rule astigmatism was more common in women (P=0.038).
  
  
  CONCLUSIONS
  More than half of the study population had refractive errors; the prevalence of myopia and astigmatism was higher than earlier studies in Iran. Since refractive errors are a major cause of avoidable visual impairment, their high prevalence in this survey is important from a public health perspective.
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Ziaei
authors.affiliation: Ophthalmic Epidemiology and Prevention of Blindness Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Marzieh
authors.initials: M
authors.lastname: Katibeh
authors.affiliation: Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Solaimanizad
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Hosseini
authors.affiliation: Department of Public Health and Biostatistics, Faculty of Health, Kashan University of Medical Sciences, Kashan, Iran ; Department of Epidemiology, Faculty of Health,Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Hamid-Reza
authors.initials: HR
authors.lastname: Gilasi
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Faegheh
authors.initials: F
authors.lastname: Golbafian
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad-Ali
authors.initials: MA
authors.lastname: Javadi
keywords: Anisometropia; Astigmatism; Elderly; Hyperopia; Myopia; Population-based Study