Visual functions in congenital night blindness.

It was shown preciously that the physiological basis of congenital night blindness probably involves a defect in neural transmission affecting primarily the scotopic (rod) mechanism. However, spectral sensitivity measurements in the dark-adapted peripheral retina indicate that rod signals, although greatly attenuated, may reach cortical centers. In spite of the decreased sensitivity, measurements of visual threshold as a function of stimulus area showed that the integrative properties of the retina ivere normal. Although toe have been unable to identify the precise nature of the defect, it appears that the abnormality affects both rod and. cone vision and extends also over the rod-free region of the fovea.