Changes in fundus reflex luminance with increased cognitive processing

A previous study using photoelectric retinoscopy at near showed an increase in fundus reflex luminance when the subject's task was changed from reading simple material to adding numbers. Unfortunately, it was not possible to attribute the luminance change to the change in cognitive task. The present experiment was designed to determine whether an increase in cognitive processing would produce an increase in fundus reflex luminance. When the subjects (N = 19, ages 22 to 27) changed from viewing 2-digit numbers at 40 cm to adding the digits, with no change in the visual stimulus, the increased in 47 of 54 trials--the mean luminance increased approximately 10% (p less than 0.01). This change in fundus reflex luminance is not attributed to change in eye position but rather to a decrease in accommodative lag.