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Five-year change in visual acuity and incidence of visual impairment: the Blue Mountains Eye Study
Suriya Foran1, Paul Mitchell, Jie Jin Wang
1Department of Ophthalmology and the Save Sight and Westmead Millennium Institutes, the University of Sydney, Sydney, Australia.
Purpose:
To describe the 5-year change in visual acuity and the incidence of visual impairment in a population-based cohort.
Design:
Population-based epidemiologic study.
Participants:
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.
Main Outcome Measures:
Visual impairment, after best refractive correction, was defined as any (visual acuity 20/40 in both eyes at baseline. Incident binocular severe visual impairment was defined as visual acuity 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
Conclusions:
This study has documented the 5-year incidence and causes of visual impairment in an older Australian population.
