Objective: To determine whether the multifocal visual evoked potential (mfVEP) technique can detect damage to the visual system in the unaffected hemifields of patients with glaucoma and unilateral hemifield defects.

Methods: Experimental study. Methods: Monocular mfVEPs and achromatic automated perimetry (AAP) were obtained in both eyes of 16 patients with open-angle glaucoma and unilateral hemifield defects. The mfVEPs were obtained using a pattern-reversal dartboard array with 60 sectors; the entire display was 44.5 degrees in diameter. For each pair of mfVEP responses an interocular ratio of root-mean-square amplitude was calculated. These values were compared with the mean values obtained from 30 control subjects. Probability plots for MfVEP were derived. A cluster analysis was used to determine whether an mfVEP hemifield was normal or abnormal.

Results: Three of 60 (5.0%) mfVEP hemifields from control subjects had significant mfVEP deficits based upon a cluster of abnormal points. Significant mfVEP deficits were detected in the affected AAP hemifield in 15 of 16 (93.8%) glaucoma patients and in 6 of 16 patients in hemifields with apparently normal AAP. The percentage of hemifields with abnormal mfVEPs, but normal AAP, was significantly higher for the glaucoma patients than for the controls (37.5% vs 5.0%, P <.001, chi square).In glaucomatous eyes with achromatic visual fields defects limited to one hemifield, the mfVEP technique can detect evidence of glaucomatous damage in the unaffected hemifield.