title: Long-term changes in visual acuity in an older population over a 15-year period: the Blue Mountains Eye Study.
abstract: OBJECTIVE
  To describe the change in visual acuity (VA) and incidence of visual impairment (VI) in an older population over a 15-year period.
  
  
  METHODS
  Population-based cohort.
  
  
  METHODS
  Of the 3654 participants of the Blue Mountains Eye Study (BMES) baseline examination from 1992 through 1994, 1149 were re-examined during the 15-year follow-up between 2007 and 2010.
  
  
  METHODS
  Best-corrected VA by means of subjective refraction was measured with a logarithm of the minimum angle of resolution chart using Early Treatment Diabetic Retinopathy Study methods at each examination.
  
  
  METHODS
  Unilateral VI was defined as VA worse than 20/40 and blindness was defined as VA worse than 20/200 in the worse eye. Incident bilateral VI and blindness were determined according to VA in the better eye at the 15-year visit. Doubling of the visual angle was defined as a loss of 15 letters or more from baseline to the 15-year visit. Halving of the visual angle was defined as a VA improvement of 15 letters or more over the same period. Causes of VI were determined at examination, by photographic grading, and from medical records.
  
  
  RESULTS
  Cumulative 15-year incidence of unilateral and bilateral VI was 12.3% (95% confidence interval [CI], 11.0-13.6) and 5.2% (95% CI, 4.3-6.1), respectively, and for unilateral and bilateral blindness, the cumulative incidence was 3.7% (95% CI, 3.0-4.4) and 0.9% (95% CI, 0.5-1.3), respectively. These incidence rates increased significantly with increasing age (P<0.01 for trend). Doubling and halving of the visual angle occurred in 6.9% (95% CI, 5.9-7.9) and 1.6% (95% CI, 1.0-2.2) of participants, respectively. Cataract accounted for 48.5% of unilateral and bilateral incident VI, followed by age-related macular degeneration (26.9%). Age-related macular degeneration accounted for 56.9% of unilateral and bilateral incident blindness cases, followed by cataract (20.7%).
  
  
  CONCLUSIONS
  These data provide population-based estimates of long-term incidence of visual impairment among older persons. Our estimate for cumulative incidence of blindness, accounting for competing risk of death, was similar to that of the Beaver Dam Eye Study (BDES) after age standardization. However, our estimate for cumulative incidence of VI was lower compared with that observed in the BDES population. This difference may be explained in part by a higher mortality rate among our population.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hong
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Elena
authors.initials: E
authors.lastname: Rochtchina
authors.forename: Calvin Sze-un
authors.initials: CS
authors.lastname: Fong
authors.forename: Ee-Munn
authors.initials: EM
authors.lastname: Chia
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001315:Australia / Q000453:epidemiology; D001766:Blindness / Q000453:epidemiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015354:Vision, Low / Q000453:epidemiology / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology*