Differences in Visual Acuity and Color Discrimination between Darker and Fairer Eyes at Lower Illuminance

Abstract

This study was conducted to clarify the difference in visual acuity and color recognition between the darker color eyes of Japanese and the fairer color eyes of Westerners at lower illuminance. A series of experiments were carried out in an experimental room in which the illuminance level could be changed. The parameters were the illuminance on a desk and the color of the subject's eyes. Ten illuminance levels, which increased geometrically from 0.001 to 30 lx, were used. The subjects comprised two groups having different eye colors. One group was made up of Japanese, who have dark eyes, and the other Europeans and North Americans with fair eyes. At each illuminance level, after 7 minutes for adaptation, each subject's visual acuity was tested using 4 types of color Landolt rings and color discrimination was tested using 12 different-color cards. The following results were obtained.
(1) For a black Landolt ring on a white background, there was very little difference between the two groups' visual acuity.
(2) For a green Landolt ring on a blue background, the visual acuity of the dark-eyes group was remarkably lower than that of the fair-eyes group.
(3) In the color discrimination test, at an illumination of 1 lx or lower, the dark-eyes group confused colors more than the fair-eyes group.
Accordingly, the differences in visual acuity and color discrimination between the two eye-color groups were only in color discrimination at lower illuminance.