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 tech nique for tracking local optic nerve damage after unilateral optic neuritis (ON). METHODS. Humphrey visual fields and mVEP recordings were obtained from thre e 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 proc edure of Sutter was used to obtain 60 local VEP responses (the mVEP) to a s caled checkerboard pattern. The mVEPs were recorded separately for monocula r stimulation of both eyes. RESULTS. Initially, all three patients had extensive visual held defects, r educed visual acuity, and depressed mVEP amplitude in regions of poor visua l held sensitivity. By 4 to 7 weeks, the fields recovered to near normal se nsitivity in most locations, and visual acuity returned to 20/20. The mVEP recovered to nearly full amplitude in all regions, but substantial delays w ere present in many locations. The delayed responses were associated with r egions of visual field loss documented during the acute phase. CONCLUSIONS. The mVEP can be used to track local optic nerve damage after u nilateral ON. This technique should be useful in observing the effects of t reatments as well as in testing hypotheses about the mechanisms underlying both the acute loss of vision and the subsequent recovery.