Scotopic sensitivity: Relation to age, dietary patterns, and smoking status

Purpose, Although previous data suggest that rod-mediated sensitivity decre ases with age, this decrease may be insignificant when only healthy individ uals younger than 65 years are considered. In this study, we assess the rel ationship between age and scotopic sensitivity loss in subjects younger tha n 65 years to determine whether scotopic sensitivity losses can be detected when confounding factors are considered (including iris color, smoking sta tus, and dietary patterns) and a large sample size is used. Methods, A tota l of 121 subjects (aged 20 to 63 years) were tested under dark-adapted (sco topic) conditions. Scotopic sensitivity was measured as absolute thresholds to a 2.8 degrees, 550-nm test presented at 6 degrees in the temporal hemir etina. Stimuli were presented in Maxwellian view. Results. When all the sub jects were considered together, there was a slight nonsignificant trend for scotopic sensitivity to decline with age (p < 0.11). This tendency was lar gely driven by the older (45 to 63 years) past and never smokers and was st atistically significant (p < 0.024 and p < 0.05, respectively) when those t wo groups were analyzed separately. Scotopic sensitivity for the younger (2 0 to 44 years) past, current, and never smokers did not decline with age. W hen all the variables were considered in a general model, dietary intake of vitamin E explained a significant amount of the variation in scotopic sens itivity (p < 0.03). No relationships were found between scotopic sensitivit y and iris color. Conclusions, Age-related losses in scotopic sensitivity b efore age 65 are slow. Moreover, individual variations in scotopic sensitiv ity for younger subjects is minimal, even in the presence of dramatic stres sors such as long-term, heavy exposure to cigarette smoke. These data sugge st that measurements of scotopic sensitivity may not be good indicators of the retinal health of individuals younger than 65 years.