The Visual Evoked Response Latency in Optic Neuritis

Abstract

One can estimate the degree of optic nerve dysfunction in optic neuritis, using the pupil as an indicator, by holding neutral filters of increasing density over the unaffected eye until the relative afferent pupillary defect can no longer be seen. We compared the pupillary defect, measured in this way, to the visual evoked response in 13 patients with recovered unilateral optic neuritis. We found that the afferent defect correlated with the difference in visual evoked response (VER) latency between the affected and unaffected eyes, but not with the change in VER amplitude. In nine of the 13 patients the difference in VER latencies between the two eyes was significantly greater than the latency delay induced in normal eyes by a filter equal to the afferent defect. We conclude that (1) balancing the pupil defect with filters in patients with optic neuritis does not balance the VER latency, and (2) in recovered optic neuritis the VER latency predicts the amount of nerve fiber loss more accurately than does the VER amplitude.