Determination of equivalent lightness of small stimulus in the elderly using cataract experiencing goggles

The research aims to obtain and to improve the equivalent lightness perceived by elderly people by using the cataract experiencing goggles. Two viewing conditions were employed, the normal viewing and the environment-stimulus independent condition. In the normal viewing condition the heterochromatic brightness matching was carried out for four colored stimuli under nine illuminance levels from 0.08 lx through 800 lx. The results showed the equivalent lightness was lower with the goggles by the amount about 10 L* unit at any illuminance level. The color appearance experiment was also carried out by the elementary color naming method, where the chromaticness, whiteness, and blackness were estimated for colored stimuli. The chromaticness decreased for lower illuminance causing the equivalent lightness to decrease. The environment-stimulus independent condition was proposed to keep the equivalent lightness of elderly people high. A colored stimulus was placed in a separated room from the subject room and its illuminance was kept constant as 200 lx, while that of the subject room was varied as in the normal viewing experiment. By this way the effect of the environment light was reduced. The result showed that the equivalent lightness was high even with goggles for all the room illuminance unlike the normal viewing condition. It was found from the two experiments that the equivalent lightness of elderly people was composed of L*achr, L*chr, and L*env.