Prognostic value of visual evoked potentials in occipital blindness following basilar artery occlusion.

Three patients suffering from sudden occipital blindness following basilar artery occlusion underwent electroretinography and visual evoked potential (VEP) examinations. The VEPs performed early in those blind patients and repeated later seem to be of prognostic value. Responses of normal shape and amplitude after monocular and binocular stimulation were followed by complete recovery of vision. Unequal and subnormal VEPs obtained following monocular stimulation, and even smaller responses reached after binocular stimulation, accompanied permanent unilateral occipital damage resulting in homonymous hemianopsia. Lack of VEP was proved to be a preceding sign of permanent blindness.