Visual evoked potential as a prognostic factor for vitrectomy in diabetic eyes.

To determine whether or not the electrophysiological status of the eye can give information as to the result of vitreous surgery, the visual evoked potential to flash stimulation was measured prior to vitreous surgery. Seventy-four eyes were submitted to surgery. Latencies of flash evoked potentials showed a distribution suggestive of a Gaussian curve with an abnormal extension. Dividing the material into 2 groups based on a latency longer or shorter than 100 millisec revealed a highly significant difference in visual improvement after surgery between patients with long latency and patients with short latency (P less than 0.001). With a latency longer than 100 millisec the patient has an almost equal chance of visual improvement or visual reduction by surgery. The frequency of operative complications was twice as high in patients with latency longer than 100 millisec compared to patients with a latency shorter than 100 millisec.