Tracking the recovery of local optic nerve function after optic neuritis: a multifocal VEP study.

PURPOSE: To explore the multifocal visual evoked potential (mVEP) as a technique for tracking local optic nerve damage after unilateral optic neuritis (ON).

METHODS

Humphrey visual fields and mVEP recordings were obtained from three patients within 7 days of an episode of ON. Patients were retested during the recovery phase, approximately 4 to 7 weeks later. The multi-input procedure of Sutter was used to obtain 60 local VEP responses (the mVEP) to a scaled checkerboard pattern. The mVEPs were recorded separately for monocular stimulation of both eyes.

RESULTS

Initially, all three patients had extensive visual field defects, reduced visual acuity, and depressed mVEP amplitude in regions of poor visual field sensitivity. By 4 to 7 weeks, the fields recovered to near normal sensitivity in most locations, and visual acuity returned to 20/20. The mVEP recovered to nearly full amplitude in all regions, but substantial delays were present in many locations. The delayed responses were associated with regions of visual field loss documented during the acute phase.

CONCLUSIONS

The mVEP can be used to track local optic nerve damage after unilateral ON. This technique should be useful in observing the effects of treatments as well as in testing hypotheses about the mechanisms underlying both the acute loss of vision and the subsequent recovery.