title: Refractive error in Nigerian adults: prevalence, type, and spectacle coverage.
abstract: OBJECTIVE
  To provide data on prevalence and types of refractive error and the spectacle-wearing rate among adults in Nigeria and the degree to which the need for distance correction could be met by off-the-shelf spectacles.
  
  
  METHODS
  Multistage, stratified, cluster random sampling with probability proportional to size was used to identify a nationally representative sample of 15,027 persons aged ≥40 years. Distance vision was measured using a reduced logMAR tumbling-E chart. All participants underwent autorefraction, and those with presenting acuity of <6/12 in one or both eyes had their corrected acuity measured and underwent detailed clinical examination to determine the cause.
  
  
  RESULTS
  Included in the survey were 13,599 (89.9%) of the 15,122 persons aged ≥40 years who were enumerated. Uncorrected refractive error was responsible for 77.9% of mild visual impairment (<6/12-6/18), 57.1% of moderate visual impairment (<6/18-6/60), 11.3% of severe visual impairment (<6/60-3/60), and 1.4% of blindness (<3/60). The crude prevalence of myopia (≤0.5 D) and high myopia (≤5.0 D) were 16.2% and 2.1%, respectively. Spectacles could improve the vision of 1279 (9.4%) and 882 (6.5%) participants at the 6/12 and 6/18 level, respectively, but only 3.4% and 4.4% of these individuals wore spectacles to the examination site. Approximately 2,140,000 adults in Nigeria would benefit from spectacles that improved their vision from <6/12 to ≥6/12. More than a third of the need could be met by low-cost, off-the-shelf spectacles.
  
  
  CONCLUSIONS
  Uncorrected refractive errors are an important cause of visual impairment in Nigeria, and services must be dramatically improved to meet the need.
authors.affiliation: Ministry of Health, Awka, Anambra State, Nigeria.
authors.forename: Christian
authors.initials: C
authors.lastname: Ezelum
authors.forename: Hessom
authors.initials: H
authors.lastname: Razavi
authors.forename: Selvaraj
authors.initials: S
authors.lastname: Sivasubramaniam
authors.forename: Clare E
authors.initials: CE
authors.lastname: Gilbert
authors.forename: Gudlavalleti V S
authors.initials: GV
authors.lastname: Murthy
authors.forename: Gabriel
authors.initials: G
authors.lastname: Entekume
authors.forename: Tafida
authors.initials: T
authors.lastname: Abubakar
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000453:epidemiology; D005139:Eyeglasses / Q000706:statistics & numerical data*; D005260:Female; D006301:Health Services Needs and Demand; D006306:Health Surveys; D006801:Humans; D006956:Hyperopia / Q000145:classification / Q000453:epidemiology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000145:classification / Q000453:epidemiology* / Q000628:therapy; D009549:Nigeria / Q000453:epidemiology; D015995:Prevalence; D012029:Refraction, Ocular / Q000502:physiology; D017678:Sex Distribution; D014792:Visual Acuity / Q000502:physiology; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*