Gene-Environment Interactions and Aging Visual Function : A Classical Twin Study

To elucidate the contribution of environmental versus genetic factors to the significant losses in visual function associated with normal aging. A classical twin study. Forty-two twin pairs (21 monozygotic and 21 dizygotic; age 57-75 years) with normal visual acuity recruited through the Australian Twin Registry. Cone function was evaluated by establishing absolute cone contrast thresholds to flicker (4 and 14 Hz) and isoluminant red and blue colors under steady state adaptation. Adaptation dynamics were determined for both cones and rods. Bootstrap resampling was used to return robust intrapair correlations for each parameter. Psychophysical thresholds and adaptational time constants. The intrapair correlations for all color and flicker thresholds, as well as cone absolute threshold, were significantly higher in monozygotic compared with dizygotic twin pairs (P