Data from 625 elderly Americans, followed for an average of 8.5 years, has revealed that those with very good or excellent vision at the beginning of the study had a 63% reduced risk of dementia over the study period. Those with poorer vision who did not visit an ophthalmologist had a 9.5-fold increased risk of Alzheimer disease and a 5-fold increased risk of cognitively impaired but no dementia. For the very-old (90+), 78% who maintained normal cognition had received at least one previous eye procedure compared with 51.7% of those with Alzheimer disease. The findings point to the need for older adults to seek treatment for their eye problems. The study raises the possibility that poor vision is not simply a symptom of developing dementia, but a contributing factor — possibly through its effect on curtailing activities which would help prevent it.
(2010). Untreated Poor Vision: A Contributing Factor to Late-Life Dementia.
Am. J. Epidemiol.. 171(6), 728 - 735.