More than 60 patients with retinal vessel occlusions were examined using the electro-oculogram (EOG) ramp test. In the course of the disease a systematic disturbance of the slow oscillation of the corneoretinal potential occurred. First, the latency of the light peak increased. Then the peak decreased and was reached up to 5 min later than in the healthy eye. In the final stage the basic level dropped to about half of the normal value and light response was absent. During the next few weeks an improvement in the basic level took place, but usually this did not involve improved vision.