Vascularity in the reptilian spectacle

sensitivity curve for 1° 200 ms. flashes on a white background may be a rather precise indicator of the functioning of the opponent-color system. Thus, although J. T. believed that his right eye was normal, the corresponding spectral sensitivity curve (continuous curve, Fig. 3) lies near the limit of the normal range, indicating that his right eye may have been partially affected by a similar defect. There is no evidence for any response from the blue-sensitive cones of J. T.'s left eye and, in this respect, the subject's defect may be classified as a tritan type. However, it may also be possible to interpret this finding in terms of a general loss of opponent-color function, since it is thought that the blue cones signal mainly through the opponent-color system. The opponent-color cells in the primate retina have axons with lower conduction velocities than the luminance cells and it is thus likely that the opponent-color axons are relatively fine. For this reason, it is possible that the proposed defect of the subject's opponent-color system may be related to selective loss or damage to small fibers or neurons.