Visual evoked potential and pupillary signs. A comparison in optic nerve disease

We measured the pupil cycle time, the relative afferent pupillary defect, and the pattern-reversal visual evoked potential (VEP) in 41 patients with unilateral anterior ischemic optic neuropathy (AION) and 24 patients with unilateral optic neuritis. We speculated that the relative afferent pupillary defect would match the VEP amplitude and that the pupil cycle time would correspond to the VEP latency. We found a correlation between the relative afferent pupillary defect and VEP amplitude in patients with AION, but not in patients with optic neuritis. We also found that the pupil cycle time and VEP latency were weakly correlated, but only in patients with optic neuritis. In these two groups of patients with unilateral optic neuropathy, the most sensitive objective indicator of disease was the relative afferent pupillary defect. The least sensitive indicator was the pupil cycle time.