Dichoptic stimulation improves detection of glaucoma with multifocal visual evoked potentials.
OBJECTIVE
To determine whether simultaneous binocular (dichoptic) stimulation for multifocal visual evoked potentials (mfVEP) detects glaucomatous defects and decreases intereye variability.


METHODS
Twenty-eight patients with glaucoma and 30 healthy subjects underwent mfVEP on monocular and dichoptic stimulation. Dichoptic stimulation was presented with the use of virtual reality goggles (recording time, 7 minutes). Monocular mfVEPs were recorded sequentially for each eye (recording time, 10 minutes).


RESULTS
Comparison of mean relative asymmetry coefficient (RAC; calculated as difference in amplitudes between eyes/sum of amplitudes of both eyes at each segment) on monocular and dichoptic mfVEP revealed significantly lower RAC on dichoptic (0.003 +/- 0.03) compared with monocular testing (-0.02 +/- 0.04; P = 0.002). In all 28 patients, dichoptic mfVEP identified defects with excellent topographic correspondence. Of 56 hemifields (28 eyes), 33 had Humphrey visual field (HFA) scotomas, all of which were detected by dichoptic mfVEP. Among 23 hemifields with normal HFA, two were abnormal on monocular and dichoptic mfVEP. Five hemifields (five patients) normal on HFA and monocular mfVEP were abnormal on dichoptic mfVEP. In all five patients, corresponding rim changes were observed on disc photographs. Mean RAC of glaucomatous eyes was significantly higher on dichoptic (0.283 +/- 0.18) compared with monocular (0.199 +/- 0.12) tests (P = 0.0006).


CONCLUSIONS
Dichoptic mfVEP not only detects HFA losses, it may identify early defects in areas unaffected on HFA and monocular mfVEP while reducing testing time by 30%. Asymmetry was tighter among healthy subjects but wider in patients with glaucoma on simultaneous binocular stimulation, which is potentially a new tool in the early detection of glaucoma.
Arvind
Hemamalini
H
Save Sight Institute, University of Sydney, Sydney, Australia. hemamalini_arvind@yahoo.com
Klistorner
Alexander
A
Graham
Stuart
S
Grigg
John
J
Goldberg
Ivan
I
Klistorner
Asya
A
Billson
Frank A
FA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009901:Optic Nerve Diseases / Q000175:diagnosis* / Q000503:physiopathology; D010775:Photic Stimulation; D012607:Scotoma / Q000175:diagnosis* / Q000503:physiopathology; D015348:Vision, Binocular / Q000502:physiology*; D058609:Visual Field Tests; D014794:Visual Fields