Alterations in critical flicker frequency as a function of age and light: dark ratio.

Binocular critical flicker frequencies (CFF's) were determined for 108 test persons in age from 13 to 89 year. Major results were (a): The relationship between CFF and age is linear and negative for all light: dark ratio levels under both conditions of surround luminance and (b) the decrement of CFF with age is a function of the light-time percentage of the flicker-cycle. The differentiation between age groups is more pronounced at the lower light-time percentages.