Effect of pupillary dilatation in flash VER testing.

Light flash transient visual evoked response (VER) testing is often a part of the perioperative evaluation of eyes with opaque media, and pupillary size in these patients may not be knowable or may be inadvisable to alter. We therefore evaluated transient light flash VER responses before and after pupillary dilation in normal controls and in patients with media opacities to evaluate the effects of pupil size on the amplitude and latency of the recorded VER. Monocular testing was performed bilaterally with a Grass PS-22 photostimulator at the S1 and S16 settings, with monopolar recordings 1 cm above the inion. One hundred twenty-eight 200-msec samplings were recorded and averaged on a Nicolet CA-1000 clinical averager. Latencies were often shorter with the stronger light stimulus, but pupillary dilation did not produce a clear trend toward shorter latencies. Overall, pupillary dilatation did not significantly increase recorded amplitudes, nor did iris color appear to be a factor. These results suggest that, under our testing conditions, pupillary dilatation is not necessary for obtaining reliable transient flash VER recordings.