The Spectral Luminosity Curves for a Dichromatic Eye and a Normal Eye in the Same Person.

We have recently had the opportunity to determine some visual functions of a unilaterally color-blind person, that is, one who demonstrates some form of color blindness in one eye and normal (trichromatic) vision in the other. The fact that a condition of unilateral color blindness can exist has been known since 1879.1 Cases of unilateral color blindness have been historically important, for it has been supposed that they could provide conclusive evidence on the chromatic perceptions of color-blind individuals. It is for this reason that most of the tests made upon them were concerned with comparisons between the colors seen in the normal and the color-blind eye. The evidence seems to show that in unilaterally color-blind subjects, any form of color deficit may be represented in the color-blind eye, e.g., dichromatism, anomalous trichromatism, or completely mono-chromatic vision. Judd2 reports that thirty-seven cases of unilateral color blindness have been described in the literature. Because of inadequate procedure or background information, the data on only eight have proved of more than passing interest. No case of unilateral color blindness so far reported has involved a color-blind eye whose discriminative functions are known in detail, and it is probable that in most of the cases reported the trichromatic eye has not met completely rigorous criteria of normality. We do not believe that these latter shortcomings apply in the case of our subject. We have made analyses of several of the visual functions exhibited by both the color-blind and the normal (trichromatic) eyes, and we are confident that the trichromatic eye of our subject does, in fact, meet the usual standards of normality. A recent paper3 by us has provided information on luminosity losses of dichro-mats. In that paper we pointed out the contradictory issues raised by the facts of luminosity losses in dichromats and the color-naming of unilaterally color-blind subjects. We have examined various visual functions of our unilaterally color-blind subject over a period of about three years, with considerable periods of interruption. (Since a later report on color mixture will show that, in her color-blind eye, she can match any spectral wave length by a mixture of 460 my and 650 mAu, we shall refer to her color blindness as a form of dichromatism.) The present paper reports the first of these studies, a description of this subject's luminosity curve for the normal and dichromatic eye. It is found that our subject, …