The visual function of patient with ocular diseases or lesions in the visual pathways and of normal subjects is measured with psychophysical techniques. These data are correlated with those obtained with electrophysiological tests of visual function. The results stained contribute to the diagnosis of ocular and neural disorders that affect vision, and are needed to characterize their nature and evolution. They are also valuable in the assessment of the effect of different forms of treatment on the outcome of these diseases.