PULFRICH PSYCHOPHYSICAL STEREO-ILLUSION AND VISUAL-EVOKED POTENTIALS IN EPIRETINAL MEMBRANE OF THE MACULA

Six patients with unilateral epiretinal membrane of the macula perceiv ed the spontaneous Pulfrich psychophysical stereo-illusion, suggesting a relative conduction delay on the side of the membrane. In three of these patients, visual-evoked potential studies were also obtained and confirmed an absolute conduction delay in the anterior pathway on the side of the epiretinal membrane in two patients and an absence of the P 100 wave on the side of the epiretinal membrane in the third patien t. It is important to recognize that the Pulfrich psychophysical stere o-illusion can be spontaneously perceived in macula disease, and there fore, the test may not always distinguish optic nerve from macula dise ase.