Equivalent lightness of elderlies investigated by cataract experiencing goggles

Abstract

People get cataract in their eyes when they age. The color perceived by the senile cataract eyes desaturates because of the environment light that scatters in the eyes by the hazy crystalline lenses. We investigated the effect of the desaturation on brightness of objects in terms of the equivalent lightness L Ã eq , which is composed of the achromatic lightness L Ã achr and the chromatic lightness L Ã chr . If the color desaturates, L Ã chr becomes smaller and consequently L Ã eq becomes smaller in the cataract eyes. L Ã eq with and without cataract experiencing goggles at room illuminances to cover mesopic to photopic level was measured. Red, yellow, green, and blue patches of size 28 3 28 arc of the visual angle were investigated with the direct heterochromatic brightness matching between the color patches and a gray scale. Both L Ã eq took about the same value. L Ã eq with goggles was then transferred to the final L Ã eq where the matching gray scale was observed without goggles to express the equivalent lightness of cataract eyes by the gray scale perceived by normal eyes. L Ã eq with goggles was lower than L Ã eq without goggles by about 10 L* units in all the four colors. This reduction was almost equal to the reduction of L* by the reduced transmittance of the goggles showing that there was no effect of color desaturation. The color appearance in the color patches was measured by the elementary color naming method, and the results clearly showed the color desaturation with goggles implying decrease of L Ã chr . We concluded that the scattered environment light compensated the decrease of L Ã chr to keep the brightness of stimuli unchanged.