Electrophysiological studies of color-blindness.

Abstract

The time course of changes in electrical excitability of the eye after 2 seconds' illumination by white light was investigated in normal and color-blind subjects. 1. The excitability curve obtained by plotting ζ-values or percentage increases in electrical excitability as ordinates against the time after the end of illumination as abscissae showed a single maximum at 2 seconds in normal subjects. In the deuteranope, two distinct elevations were found on the excitability curve, while the curve taken from the protanope showed a single maximum At one second. 2. The excitability curve for white light obtained from deuterano-malous subjects showed distinct three elevations which were termed R, G and Bin the order of rapidity of development. It was shown that the three elevations represent three independent processes but not different phases of one and the same process. The development of the G process is weak in the deuteranomalous and entirely lacking in the deuteranope, so that there appear only two elevations in the excitability curve of the deuteranope. 3. The G elevation of the excitability curve taken from deuteranomal-ous subjects disappeared at a sufficiently low intensity of illumination, so that the excitability curve taken under such conditions could not be dis-tinguished from that of the deuteranope. 4. The wave-lexxgth dependence or spectral locus of each color pro-cess was investigated. The locus of the B process has its maximum at about 460mμ in all cases of normal and color-blinds. The R locus could not be found in the protanope, and the G locus was found lacking in the deut-eranope. The R and G loci obtained from the color-blinds had a maximum at 610 mμ and 530 mμ respectively. The locations of these maxima did not coincide precisely with those of the corresponding loci taken from the fovea of normal man, but showed a close agreement with those of the cor-responding loci taken from a parafoveal region of the retina of normal man. In the deuteranomalous, the B and R loci showed normal behavior in all respects, but the G locus was found always smaller than normal not only in the maximum height but also in the extent of the locus over the spectrum. In one case of the deuteranomalous, the G process extended over such a narrow range of the spectrum as between 490mμ and 570mμ. It is worthy of note that the defect in color vision was so severe in this case that it could not be distinguished from a true deuteranope by tho routine anomaloscopic test and by our method of excitability curves for white light.