Electrophysiological tests evaluate the function of the different structures constituting the visual nervous pathways (retina, optic nerve, optic tract, and chiasm, radiation and cerebral cortex). Among the various electrophysiological examinations, two very important tests are Electroretinograms (ERGs), which study the various retinal components, and Visual Evoked Potentials (VEPs) which study the visual pathway. These tests provide objective information on the function of the visual system even in those cases in which opacities of dioptric means (cataract, corneal leukoma) do not allow the direct observation of the retina and optic nerve, and may provide functional information in advance of structural changes.