Large rod-like photopic signals in a possible new form of congenital night blindness.

A 10-year-old Persian girl has symptoms of congenital stationary night blindness and some drusen-like lesions in the region of the vascular arcades. Her electroretinogram shows no rod response to a weak stimulus, but a large (475 microV) slow scotopic response to a strong stimulus that is unchanged by photopic conditions (15 Fl background illumination). However, the response to flicker had the typical (smaller) amplitude of a cone signal. They may represent a new form of night blindness in which rod sensitivity is reduced so that there is no vision under dim conditions but rod function still persists under photopic conditions.