PURPOSE: To evaluate the usefulness of a liquid crystal display (LCD) with higher driving frequency and shorter response time (2 ms) as a visual stimulator to elicit pattern reversal visually evoked potentials (p-VEPs). METHOD: p-VEPs were recorded from 12 eyes of 12 healthy volunteers (28.3 ± 9 years). The p-VEPs elicited by a conventional cathode ray tube (CRT) screen were compared to those elicited by a high-speed LCD screen (2-ms LCD, GD245HQbid, Acer, Taipei, Taiwan). The luminance changes of each monitor were measured with a photodiode. RESULTS: During the reversal phase the luminance of the 2-ms LCD screen with 97% contrast was transiently reduced, which can elicit an electroretinogram (ERG) and therefore a flash VEP. The 2-ms LCD with 81% contrast checkerboard had a minimal luminance reduction during the reversal phase, and therefore no ERGs were elicited. No significant differences in the amplitude of P100 and the implicit times of N75 and P100 were observed in the p-VEPs elicited by a CRT or the 2-ms LCD screens as stimulators. CONCLUSION: The luminance change can elicit flash VEPs, and this artifact can be minimized by using a 2-ms LCD screen with reduced contrast of the checkerboard stimulus.
PURPOSE: To evaluate the usefulness of a liquid crystal display (LCD) with higher driving frequency and shorter response time (2 ms) as a visual stimulator to elicit pattern reversal visually evoked potentials (p-VEPs). METHOD: p-VEPs were recorded from 12 eyes of 12 healthy volunteers (28.3 ± 9 years). The p-VEPs elicited by a conventional cathode ray tube (CRT) screen were compared to those elicited by a high-speed LCD screen (2-ms LCD, GD245HQbid, Acer, Taipei, Taiwan). The luminance changes of each monitor were measured with a photodiode. RESULTS: During the reversal phase the luminance of the 2-ms LCD screen with 97% contrast was transiently reduced, which can elicit an electroretinogram (ERG) and therefore a flash VEP. The 2-ms LCD with 81% contrast checkerboard had a minimal luminance reduction during the reversal phase, and therefore no ERGs were elicited. No significant differences in the amplitude of P100 and the implicit times of N75 and P100 were observed in the p-VEPs elicited by a CRT or the 2-ms LCD screens as stimulators. CONCLUSION: The luminance change can elicit flash VEPs, and this artifact can be minimized by using a 2-ms LCD screen with reduced contrast of the checkerboard stimulus.