Beaver Dam Eye Study shows marked change in impairment with age

An assessment of the cumulative incidence of changes in visual acuity for a 15-year period showed that, overall, 8% of participants in the Beaver Dam Eye Study of age-related eye conditions developed visual impairment, 1% developed severe impairment, and 7% developed doubling of the visual angle.

Data also showed a marked change in impairment with increasing age, said Barbara E.K. Klein, MD, MPH, professor of ophthalmology and visual sciences, University of Wisconsin School of Medicine and Public Health, Madison.

"People who were 75 and older at the baseline had about 12.8% times the odds of developing a visual impairment," Dr. Klein said. These individuals, born in the 1903-1907 cohort, were more likely than those born in later cohorts to develop visual impairment; the difference was statistically significant.

It is possible that advances in prevention and treatment of age-related diseases have influenced the differences between younger and older cohorts, Dr. Klein said. However, it may not be possible to analyze that hypothesis with the data from this study, particularly given the declining number of participants due to mortality.

Data also indicated that age-related macular degeneration was the most common cause of severe impairment, accounting for 52% of cases. Cataract and retinal vein occlusion were each responsible for 12% of incidents, while the rate of diabetic retinopathy was surprisingly low at 3%, Dr. Klein said.

The Beaver Dam Study was funded by the National Eye Institute to collect data on the prevalence and incidence of several age-related eye conditions. A private census identified approximately 6,000 individuals between the ages of 43 and 86 in the city and township of Beaver Dam, WI.

Approximately 5,000 of these individuals participated in baseline examinations between 1988 and 1990. At 5-, 10-, and 15-year intervals, all living members of this group were invited to follow-up examinations. Fifteen-year follow-up was completed in May 2005. Visual acuity was measured using Early Treatment for Diabetic Retinopathy Study protocols at all time points.