Repeat reliability of the multifocal visual evoked potential in normal and glaucomatous eyes

To investigate the repeat reliability of the multifocal visual evoked potential (mfVEP).

Fifteen subjects with no known abnormalities of the visual system and 10 patients with glaucoma participated in the study. Monocular mfVEPs were recorded on two separate days, using a 60-sector, pattern-reversal dart board array. Within a single session, two 7-minute. recordings were obtained for each eye. The amplitude of each mfVEP response was obtained using a root mean square measure (RMS). An mfVEP ratio [10*log (RMS day 1 / RMS day 2)] provided a measure of the reproducibility of an individual response. The same calculations were performed for Run 1 compared with Run 2 within a day and Run 1 (Run 2) compared with Run 1 (Run 2) across days.

For all 1800 mfVEP responses (60 sectors x 15 subjects x 2 eyes), the correlation between the amplitude on day 2 and the amplitude on day 1 was good (r = 0.85). The mean standard deviation (SD) of the 60 mfVEP ratios for the individual subjects was 1.63 dB for the 14-minute records (the combination of the two 7-minute recordings). On average for the 7-minute records, the mean SD across days was 1.77 dB while the mean SD within a day was 1.53 dB. The correlation within a day (r = 0.87) also was slightly larger than across days (r = 0.80). The mean SD decreased as the RMS amplitude increased. The patients' mean SD was 1.75 dB with r equal to 0.82.

The repeat reliability of the mfVEP was good (approximately 1.6dB); in fact, it was better than that typically obtained with static automated perimetry (approximately 2.7dB). Repeat testing on separate days added surprisingly little to the variability seen with repeat testing within the same session.