Visual evoked potentials with CRT and LCD monitors: when newer is not better.

BACKGROUND

The stimulus for pattern reversal visual evoked potentials (PRVEP) has traditionally been delivered by a cathode ray tube (CRT) monitor. Liquid crystal display (LCD) monitors have become more affordable and are being used instead of CRT monitors for many applications. We tested the hypothesis that LCD monitors were equivalent to CRT monitors when used for PRVEP.

METHODS

Monocular, full field PRVEP with a 32' check size were obtained in six normal subjects with a CRT monitor and LCD monitors having 2 msec, 8 msec, and 30 msec response times. The average P100 latency with the CRT screen was compared to the latencies with the LCD screens.

RESULTS

The mean P100 latency of the CRT monitor was 107.7 (+/-6.6) ms, for the LCD 2 msec monitor was 115.7 (+/-6.9; p < 0.0001) ms, for the LCD 8 msec monitor was 118.5 (+/-6.5; p < 0.0001) ms, and the LCD 30 msec monitor was 156.8 (+/-6.8; p < 0.0001) ms.

CONCLUSIONS

Currently available liquid crystal display (LCD) monitors do not provide data comparable to cathode ray tube (CRT) monitors. LCD monitors cannot replace CRT monitors for pattern reversal visual evoked potentials unless new normative data are obtained.