Slow pattern-reversal stimulation facilitates the assessment of retinal function with multifocal recordings.

OBJECTIVE

The use of the multifocal pattern electroretinogram (mfPERG) for objective visual field testing is critically impaired by the small signal-to-noise ratios (SNRs) obtained. In order to explore ways to enhance mfPERG-SNRs and mfPERG-magnitude, the dependence of mfPERGs and multifocal visual evoked potentials (mfVEPs) on stimulation rate and stimulation mode is examined.

METHODS

Using VERIS Science 5.1.10X (EDI, CA, USA) mfPERGs and mfVEPs were recorded simultaneously in two different experiments to stimulation at 52 locations comprising a visual field of 44 degrees diameter. Firstly, in eight subjects the response magnitudes were compared for three pattern-reversal (PR) and two pattern-onset (PO) stimulus conditions, which differed in their maximal stimulation rate. Secondly, for equal recording durations the signal-to-noise-ratios (SNRs) of four PR stimuli with different stimulation rates were determined in eight subjects.

RESULTS

Both mfPERG and mfVEP response magnitudes were substantially enhanced for the lower stimulation rates. The greatest effects were obtained for the mfPERG-N95 to pattern-reversal stimulation, which was by a factor of 5.2+/-0.6 greater than that N95 for the standard condition (p<0.001). mfPERGs for a comparatively low stimulation rate, i.e., reversing its contrast with a probability of 50% only every 53 ms, yielded the greatest SNRs (1.42-fold greater than for the standard condition; p<or=0.002).

CONCLUSIONS

The enhancement of both mfPERG and mfVEP response magnitudes for slow stimulation suggests that retinal mechanisms contribute to this response enhancement and that slow pattern-reversal stimulation might facilitate simultaneous high-resolution mfPERG- and mfVEP-based visual field testing.

SIGNIFICANCE

The study suggests that mfPERG-based assessment of retinal ganglion cell function can be improved with stimulation sequences that are 2-4 times slower than the standard multifocal stimulus.