Rod- and cone-mediated visual function in multiple sclerosis.

Visual thresholds and perceptual latencies were determined in patients with multiple sclerosis (MS) and in normal control subjects. Measurements were made under light- and dark-adapted conditions, with stimuli chosen to stimulate rod and cone receptors selectively. More abnormalities in perceptual latency and luminance threshold were recorded in the light-adapted condition than in the dark-adapted condition, but this result was not specific to the rod or cone systems. Possible underlying pathophysiological processes are discussed, and it is suggested that reduced conduction velocity in the demyelinated visual pathway is the most likely explanation of the observed perceptual delays and that there is no evident retinal contribution.