title: Prevalence of the refractive errors by age and gender: the Mashhad eye study of Iran.
abstract: BACKGROUND
  Refractive errors are a common eye problem. Considering the low number of population-based studies in Iran in this regard, we decided to determine the prevalence rates of myopia and hyperopia in a population in Mashhad, Iran.
  
  
  METHODS
  Cross-sectional population-based study.
  
  
  METHODS
  Random cluster sampling. Of 4453 selected individuals from the urban population of Mashhad, 70.4% participated.
  
  
  METHODS
  Refractive error was determined using manifest (age > 15 years) and cycloplegic refraction (age ≤ 15 years). Myopia was defined as a spherical equivalent of -0.5 diopter or worse. An spherical equivalent of +0.5 diopter or worse for non-cycloplegic refraction and an spherical equivalent of +2 diopter or worse for cycloplegic refraction was used to define hyperopia.
  
  
  METHODS
  Prevalence of refractive errors.
  
  
  RESULTS
  The prevalence of myopia and hyperopia in individuals ≤ 15 years old was 3.64% (95% CI: 2.19-5.09) and 27.4% (95% CI: 23.72-31.09), respectively. The same measurements for subjects > 15 years of age was 22.36% (95% CI: 20.06-24.66) and 34.21% (95% CI: 31.57-36.85), respectively. Myopia was found to increase with age in individuals ≤ 15 years and decrease with age in individuals > 15 years of age. The rate of hyperopia showed a significant increase with age in individuals > 15 years. The prevalence of astigmatism was 25.64% (95% CI: 23.76-27.51).
  
  
  CONCLUSIONS
  In children and the elderly, hyperopia is the most prevalent refractive error. After hyperopia, astigmatism is also of importance in older ages. Age is the most important demographic factor associated with different types of refractive errors.
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: Abbasali
authors.initials: A
authors.lastname: Yekta
authors.forename: Javad
authors.initials: J
authors.lastname: Heravian
authors.forename: Farhad
authors.initials: F
authors.lastname: Rezvan
authors.forename: Hamidreza
authors.initials: H
authors.lastname: Ghadimi
authors.forename: Bijan
authors.initials: B
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; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000453:epidemiology* / Q000503:physiopathology; D012189:Retrospective Studies; D017678:Sex Distribution; D014505:Urban Population; D055815:Young Adult