Even in the absence of eye disease, our vision will worsen as we age. What causes it, and what can be done to stop it? To answer that, researchers at the University of Melbourne, in Australia, looked at environmental vs. genetic factors of visual loss associated with normal aging.

The researchers examined 42 pairs of twins (21 identical and 21 fraternal) between the ages of 57 and 75 without eye disease. When test results showed that visual ability declined at about the same age in identical twins, the trait was assumed to be genetic. When the decline occurred at different ages, environmental factors were considered dominant. The researchers then compared the results of identical twins against fraternal twins.

Their results indicate that cone cells appear subject to genetic factors while rod cells are influenced by environmental factors.

Specifically, genetic factors appear to be strong determinants of sharp visual acuity and color discriminationfunctions performed by cone cells pathways.

Genetic factors were not strongly correlated with night vision and the ability to adapt to light level changes, which are performed by retinal rod cells. This finding suggests that environmental influences are important to those functions.

Our results support clinical and research efforts now underway to slow or stop age-related vision decline by modifying lifestyle factors and/or using specific medications, says lead author Ruth E. Hogg, Ph.D.

Hogg RE, Dimitrov PN, Dirani M, et al. Gene-environment interactions and aging visual function: a classical twin study. Ophthalmology 2009 Feb;116(2):263-9.

Vol. No: 146:03Issue: 3/15/2009