title: A proposed rapid methodology to assess the prevalence and causes of blindness and visual impairment.
abstract: OBJECTIVE
  To determine whether a sample of the 50-year-old and above population would provide comparable information to a total population-based survey.
  
  
  METHODS
  In 1996, a national eye survey of the total population in The Gambia was undertaken and the results concerning the prevalence and distribution of blindness and low vision have been reported. The same data set was used to analyse the prevalence and causes of blindness and low vision in people aged 50 years and above, and to compare the findings with the total population.
  
  
  RESULTS
  Of 55 bilaterally blind people in the total population, 83.6% were 50 years of age or older. The distribution by cause of blindness was similar for the total population and for those aged 50 years and above. Cataract and uncorrected aphakia accounted for 46% and 13%, respectively, in the total population and 48% and 15% in the 50 year and above age group. Trachoma accounted for 5% and 4%, and other corneal opacities for 16% and 13%, respectively. Phthisis bulbi, which may follow perforated corneal ulcers, ocular trauma/surgery or occasionally severe uveitis, accounted for 4% in both age groups, and glaucoma accounted for 9% in the total population and 11% in the 50 year plus group.
  
  
  CONCLUSIONS
  Assessment of the 50 year and above age group proved to be a good indicator for the causes of blindness and visual impairment in the total population and for determining those causes of blindness that are avoidable. Such an assessment requires a much smaller sample size, less than 20% of the sample size for the total population, and is likely to be less expensive.
authors.affiliation: International Centre for Eye Health, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Brendan
authors.initials: B
authors.lastname: Dineen
authors.forename: Allen
authors.initials: A
authors.lastname: Foster
authors.forename: Hannah
authors.initials: H
authors.lastname: Faal
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001035:Aphakia / Q000150:complications; D001766:Blindness / Q000453:epidemiology / Q000209:etiology; D002386:Cataract / Q000150:complications; D002648:Child; D002675:Child, Preschool; D005260:Female; D005714:Gambia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D015995:Prevalence; D012307:Risk Factors; D017678:Sex Distribution; D014141:Trachoma / Q000150:complications; D014392:Tuberculosis, Ocular / Q000150:complications; D015354:Vision, Low / Q000453:epidemiology / Q000209:etiology