title: Prevalence and causes of visual impairment according to World Health Organization and United States criteria in an aged, urban Scandinavian population: the Copenhagen City Eye Study.
abstract: OBJECTIVE
  To evaluate the prevalence and causes of visual impairment in an epidemiologic study of aged, urban individuals in Denmark.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  The study population consisted of 1000 randomly selected residents aged 60 to 80 years in Copenhagen, Denmark. Of 976 eligible persons, 946 (96.9%) could be examined. Information about best-corrected visual acuity (VA) was obtained from 944 cooperative persons (96.7%).
  
  
  METHODS
  Data from the Copenhagen City Eye Study were used to assess the cause-specific prevalence of visual impairment as defined by the World Health Organization (WHO) (VA worse than 20/60-20/400 in the better eye) and the criteria used most commonly in the United States (VA worse than 20/40 but better than 20/200 in the better eye). Eligible subjects underwent an extensive ophthalmologic examination at The National University Hospital of Denmark.
  
  
  METHODS
  Best-corrected VA and primary causes of visual impairment.
  
  
  RESULTS
  The prevalence of low vision according to the WHO definition ranged from 2.6% in subjects aged 70 to 74 years to 4.8% in subjects 75 to 80 years of age, with an age-adjusted relative prevalence of 1.58%. Using the U.S. definition, the overall age-adjusted prevalence of visual impairment was 2.9%. The causes of visual impairment according to the WHO criteria were age-related macular degeneration (AMD) (44.4%), cataract (33.3%), glaucoma in combination with cataract (11.1%), myopic macular degeneration (5.6%), and diabetic retinopathy (5.6%). However, according to the U.S. criteria, cataract was the most frequent primary cause (50.0%) and AMD was the second most frequent primary cause (34.4%) of visual impairment. Furthermore, using the U.S. criteria diabetic retinopathy was revealed as equally important as AMD and cataract as a cause of visual impairment among persons aged 65 to 69 years (33.3%).
  
  
  CONCLUSIONS
  Increasing age was an independent predictor of visual impairment. Cataract and AMD were the leading causes. Adequate implementation of surgery to treat cataract could reduce visual impairment by 33.3% according to the WHO criteria and by 50% according to the U.S. criteria.
authors.affiliation: Department of Ophthalmology E 2061, the National University Hospital (Rigshospitalet), Blegdamsvej 9, DK-2100 Copenhagen, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Buch
authors.forename: T
authors.initials: T
authors.lastname: Vinding
authors.forename: N V
authors.initials: NV
authors.lastname: Nielsen
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002386:Cataract / Q000150:complications / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D003930:Diabetic Retinopathy / Q000150:complications / Q000453:epidemiology; D005260:Female; D006801:Humans; D008268:Macular Degeneration / Q000150:complications / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014505:Urban Population / Q000706:statistics & numerical data*; D015354:Vision, Low / Q000453:epidemiology* / Q000209:etiology*; D014792:Visual Acuity; D014944:World Health Organization