title: Five-year change in visual acuity and incidence of visual impairment: the Blue Mountains Eye Study.
abstract: OBJECTIVE
  To describe the 5-year change in visual acuity and the incidence of visual impairment in a population-based cohort.
  
  
  METHODS
  Population-based epidemiologic study.
  
  
  METHODS
  Of the 3654 participants of the Blue Mountains Eye Study (BMES I) baseline examination (aged 49 years+ during 1992-1994), 2335 were reexamined during the 5-year follow-up examinations from 1997 to 1999 (BMES II), and 543 persons had died since BMES I.
  
  
  METHODS
  Visual acuity was measured using a logarithm of the minimum angle of resolution chart in both eyes separately before and after standardized refraction. Pupils were dilated and a detailed examination was performed.
  
  
  METHODS
  Visual impairment, after best refractive correction, was defined as any (visual acuity </=20/40; </=41 letters) and severe (visual acuity </=20/200; 0-5 letters) in keeping with the Beaver Dam Eye Study. Incident binocular visual impairment was defined as visual acuity </=20/40 in both eyes at follow-up, where visual acuity was >20/40 in both eyes at baseline. Incident binocular severe visual impairment was defined as visual acuity </=20/200 in both eyes at follow-up, where visual acuity was >20/200 in both eyes at baseline. The incidence for three other levels of visual impairment is also given: <20/40, <20/70, and <20/200. Monocular visual impairment was defined as impairment in one eye only at follow-up, where both eyes were unimpaired at baseline. Incident doubling and halving of the visual angle were calculated.
  
  
  RESULTS
  Incidence rates for visual impairment increased significantly with age. Any incident impairment </=20/40 occurred binocularly in 41 persons (1.9%) and monocularly in 150 persons (7.1%). Severe incident impairment </=20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (2.1%). Incident impairment <20/40 occurred binocularly in 37 persons (1.7%) and monocularly in 134 persons (6.3%). Impairment <20/70 occurred binocularly in 15 persons (0.7%) and monocularly in 84 persons (3.8%). Impairment <20/200 occurred binocularly in 3 persons (0.1%) and monocularly in 44 persons (1.9%). Women consistently had a higher incidence of visual impairment than men, although this was often not statistically significant after adjusting for age. Increasing age was a strong predictor of visual impairment.
  
  
  CONCLUSIONS
  This study has documented the 5-year incidence and causes of visual impairment in an older Australian population.
authors.affiliation: Department of Ophthalmology and the Save Sight and Westmead Millennium Institutes, the University of Sydney, Sydney, Australia.
authors.forename: Suriya
authors.initials: S
authors.lastname: Foran
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009517:New South Wales / Q000453:epidemiology; D017678:Sex Distribution; D014786:Vision Disorders / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D015348:Vision, Binocular; D014792:Visual Acuity / Q000502:physiology; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*