title: Causes of visual impairment in two older population cross-sections: the Blue Mountains Eye Study.
abstract: OBJECTIVE
  To describe the causes of bilateral and unilateral blindness and visual impairment in two cross-sections of an older Australian population 6 years apart.
  
  
  METHODS
  The Blue Mountains Eye Study examined 3654 persons aged 49-97 years during 1992-1994 (population cross-section 1). Cohort survivors (2335) and 1174 persons who moved to the area or reached an eligible age were examined during 1997-2000, a total of 3509 persons (population cross-section 2). LogMAR visual acuity was measured after standardized refraction. Blindness and visual impairment were respectively defined by visual acuity <6/60 and <6/12. Causes were determined for the two temporal cross-sections.
  
  
  RESULTS
  Age-related macular degeneration (AMD) was the principal cause of bilateral and unilateral non-correctable blindness in both cross-sections. AMD caused 77% of bilateral blindness in Cross-section 1 and 50% in Cross-section 2. Cataract, glaucoma, corneal and neurological disease were next equally frequent causes (6% each) of bilateral blindness in Cross-section 1. In Cross-section 2, cataract ranked as the third most frequent principal cause (10%) after other retinal diseases (40%). The proportion of unilateral blindness with AMD as principal cause was very similar (around one-third of cases) in the two cross-sections; while in Cross-section 2 blindness was less frequently caused by cataract (19% vs. 13%). Cataract was the principal cause of both bilateral and unilateral visual impairment, responsible for 50% of bilateral (better eye) and 35-40% of unilateral (worse eye) impairment, with slightly lower rates found in Cross-section 2 than in Cross-section 1. AMD was consistently the second most frequent cause, causing one-third of bilateral and one-fifth of unilateral visual impairment.
  
  
  CONCLUSIONS
  These data indicate a relative stable pattern of causes for blindness and visual impairment, with AMD and cataract, respectively, dominating these two levels.
authors: Department of Ophthalmology, University of Sydney (Centre for Vision Research, Westmead Hospital) and the Westmead Millennium and Save Sight Institutes, Sydney, Australia.
authors: Suriya
authors: S
authors: Foran
authors: Jie Jin
authors: JJ
authors: Wang
authors: Paul
authors: P
authors: Mitchell
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology* / Q000209:etiology*; D002386:Cataract / Q000150:complications / Q000453:epidemiology; D003316:Corneal Diseases / Q000150:complications / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D005901:Glaucoma / Q000150:complications / Q000453:epidemiology; D006306:Health Surveys; D006801:Humans; D008268:Macular Degeneration / Q000150:complications / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009517:New South Wales / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*