Flash visual evoked potential as a prognostic factor for vitreous operations in diabetic eyes

In 116 diabetic eyes scheduled for vitreous surgery, the visual evoked potential (VEP) after flash stimulation was recorded prior to surgery. Latencies of the flash evoked potentials show a distribution suggestive of a Gaussian curve with an abnormal extension. Dividing the material into two groups based on a latency shorter or longer than 100 milliseconds revealed a highly significant difference in the visual improvement following surgery between patients with a short and patients with a long latency (P less than 0.001). With a latency longer than 100 millisec. most patients showed no visual change after operation, and among the few who did the change, consisted more often in visual reduction than improvement. Additional investigations in the study reveal that it is likely that the prolonged latency of the flash VEP is due to pathology of the retina or visual pathways.