title: Population-based study of presbyopia in Shahroud, Iran.
abstract: BACKGROUND
  There is limited information regarding the prevalence of presbyopia in different parts of the world. The add power and the prevalence of presbyopia by age and gender in general population of Shahroud, north of Iran, were studied.
  
  
  METHODS
  Population-based cross-sectional study.
  
  
  METHODS
  Using random cluster sampling, 6311 people from the 40- to 64-year-old population of Shahroud were invited. Of the invited population, 5190 individuals (82.2%) participated in the study.
  
  
  METHODS
  Presbyopia was defined as the correction of near vision to logMAR 1 (N8 point) with at least 1 D of add power.
  
  
  METHODS
  Near visual acuity of participants was evaluated with a logMAR chart at a distance of 40 cm.
  
  
  RESULTS
  Mean add power in the age groups of 40-44, 45-49, 50-54, 55-59 and 60-64 years was 0.65, 1.30, 1.70, 1.87 and 2.08 D, respectively. For each 5-year increase in age, a 0.35 D increase in add power was noted. The prevalence of presbyopia was 58.15% (95% confidence interval: 56.46-59.84). Presbyopia was more prevalent in women (P < 0.001) and increased with ageing more in women than in men (P < 0.001). Furthermore, in the 60-64-year-old age group, 11% of men and 23% of women were not presbyopic.
  
  
  CONCLUSIONS
  Compared with other reports, the add power in different age groups was 0.5 D less, and presbyopia was less prevalent. More than 50% of the over 45-year-old individuals were presbyopic and 17% of the over 60 individuals were free of this condition.
authors.affiliation: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Jafarzadehpur
authors.forename: Shiva
authors.initials: S
authors.lastname: Mehravaran
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Emamian
authors.forename: AbbasAli
authors.initials: A
authors.lastname: Yekta
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shariati
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D044382:Population Groups; D011305:Presbyopia / Q000453:epidemiology*; D015995:Prevalence; D012030:Refractive Errors / Q000175:diagnosis; D012307:Risk Factors; D017678:Sex Distribution