SHIFT OF EQUILUMINANCE IN CONGENITAL COLOR-VISION DEFICIENCIES - PATTERN-ERG, VEP AND PSYCHOPHYSICAL FINDINGS

We compared electrophysiological responses [pattern-ERG (PERG) and VEP ] and psychophysical measures to color stimuli to separate different f orms of anomalous color vision. PERG and VEP were recorded from seven normals and 14 subjects with congenital color vision deficiencies. Sti muli were color checkerboards with 0.5 deg check size, phase reversing at 34 rev/sec. The luminances of the red and green parts were varied in opposite direction from 0 to 30 cd/m(2), while the hue of individua l squares and space-averaged luminance were held constant. This allowe d for one equiluminance condition where flicker appeared fused. In the seven normals, the subjective equiluminance was reached at a luminanc e ratio red/(red + green) = 0.50 - 0.53. At that point, the PERG ampli tude was moderately, and the VEP amplitude sharply reduced. In 14 colo r anomalous subjects both the PERG and VEP were sharply reduced at equ iluminance. These dips were shifted compared to normals and the dip po sition corresponded to the predicted luminance ratios obtained by calc ulations from L- and M-cone activation using the Smith-Pokorny transfo rmation. As we found a close correlation of the VEP-dip position and t he anomalous quotient, these electrophysiological measures may allow o bjective assessment of color vision deficiencies. (C) 1997 Elsevier Sc ience Ltd.