Psychophysical evidence for more than two kinds of cone in dichromatic color blindness

Science  22 Jan 1982:
Vol. 215, Issue 4531, pp. 417-419
DOI: 10.1126/science.6977184


Psychophysical evidence shows that at least some classically diagnosed dichromats have three cone types rather than two. The anomalous cones, previously thought to be absent, are less sensitive than normal cones to both spectral and temporal variations, and have spectral sensitivities like those of the abnormal cones of anomalous trichromats. These results are not consistent with either loss or replacement models of X-linked recessive color-vision defects, since some dichromats apparently have the same three photopigments as anomalous trichromats.