Correlation between full-field and multifocal VEPs in optic neuritis

To compare performance of multi-focal and full-field Visual Evoked Potentials (VEP) in patients with optic neuritis (ON).

26 patients with unilateral ON were enrolled. Multi-focal VEP (MF VEP) was recorded using AccuMaptrade mark system. Four bipolar channels were analysed. Full-field VEP (FF VEP) was performed according to ISCEV standard using ESPION with frontal-occipital electrode placement. Pattern-reversal protocol was implemented with check size of 60' and field of view of 30 degrees .

For both tests amplitude and latency of affected eye were statistically different from non-affected eye. The asymmetry of amplitude and latency between two eyes was also very similar for both tests. Averaged Relative Asymmetry Coefficient of amplitude (RAC) for the FF VEP was 0.10 +/- 0.15 and for the MF VEP was 0.12 +/- 0.12 (P = 0.21, paired t-test). Averaged latency difference between affected and non-affected eyes was 13.0 +/- 12 ms for FF and 14.1 +/- 11.1 ms for MF VEPs (P = 0.14, paired t-test). Coefficient of correlation (r) of p100 component of the FF VEP and averaged MF VEP was 0.60 (P < 0.0001) for amplitude and 0.79 (P < 0.0001) for latency. Correlation improved when amplitude and latency asymmetry between two eyes was analysed (r = 0.81 and r = 0.92 respectively). Overall 73% of affected eyes were identified as abnormal by amplitude and/or latency of the FF VEP and 89% was considered abnormal when MF VEP was used. Analysis of individual cases revealed superior performance of MF VEP in detecting small or peripheral defects.