Voluntary suppression of the multifocal electroretinogram.

OBJECTIVE

To describe multifocal electroretinogram (mfERG) responses in 2 patients with nonorganic visual loss and in 11 eyes of 6 healthy persons who suppressed their mfERG responses.

DESIGN

Observational case series.

METHODS

The mfERG results were recorded in all individuals using the Veris Science 4.2 instrument. All subjects were instructed to adjust the hexagonal test pattern so that it was in best focus. A second mfERG was recorded subsequently in volunteers who attempted suppression with inattention and poor fixation and by adjusting the focus to greatest blur.

MAIN OUTCOME MEASURES

Amplitude and latency of mfERG responses.

RESULTS

Suppressed mfERGs in patients with nonorganic visual loss and healthy volunteers demonstrated reduced amplitude, especially centrally. Amplitude reduction was statistically significant in the postsuppression as compared with the presuppression recordings in wave forms N1 and N2. Statistically significant shortening of postsuppression implicit times of P1 and N2 waveforms also was demonstrated.

CONCLUSIONS

The mfERG responses may be suppressed voluntarily. Amplitude may be reduced. In contrast to most reported pathologic conditions, the implicit time is shortened.