Binocular summation in visual evoked cortical potential in patients who have significantly different P100 peak latencies in their two eyes.

Abstract

To determine whether binocular summation in visual evoked cortical potential (VEP) is present in patients who have significantly different P100 peak latencies in their two eyes. Twelve patients with unilateral optic neuritis (ON) and 11 normal controls were studied. All of them had visual acuity of > or = 20/20 in both two eyes and good stereoacuity. Transient and steady-state VEPs were recorded with monocular and binocular pattern-reversal stimulation. In normal controls, the binocular summation ratio was 1.05 with transient stimulation and 1.21 with steady-state stimulation, and in ON patients it was 1.19 and 1.30, respectively. In ON patients, the peak latency of P100 components was delayed significantly when the affected eye was stimulated, but with binocular stimulation the waveform was very similar to that when the fellow eye was stimulated. Binocular summation of VECP is not present in ON cases with large differences in the peak latency between the two eyes even if they have good stereoacuity. Binocular summation may not be correlated with stereopsis in adults whose binocular function has already matured.