'Unilateral cone dystrophy': ERG changes implicate abnormal signaling by hyperpolarizing bipolar and/or horizontal cells.

The two cases described here appear to represent the infrequently reported entity of "unilateral cone (cone-rod) dystrophy." Both cases give the suggestion that daylight vision can be affected by abnormalities in visual signals in the proximal retina, after they leave the cone photoreceptors themselves. The ERG waveform changes in these two cases are consistent with a deficit in signaling by the hyperpolarizing bipolar cells, and the complaint of abnormal color perception in both cases presented here raises the possibility that the OFF-pathway through hyperpolarizing bipolar cells may be important for color processing.