title: Liquid crystal display screens as stimulators for visually evoked potentials: flash effect due to delay in luminance changes.
abstract: OBJECTIVE
  The cathode-ray tube (CRT) screen has recently been replaced by liquid crystal display (LCD) screens as visual stimulators for pattern-reversal visually evoked potentials (p-VEPs). The aim of the study was to evaluate the usefulness of LCD screen to elicit p-VEPs.
  
  
  METHODS
  The waveforms of the p-VEPs elicited by a LCD panel were compared with those elicited by a conventional CRT screen. The changes in the luminance of each screen were measured with a photodiode, and the mean luminance change was measured with a luminance meter. VEPs and electroretinograms (ERGs) were also recorded when the monitor was covered by a diffuser.
  
  
  RESULTS
  The p-VEPs elicited by the LCD consisted of the N75 and P100 components of the conventional VEPs and had good reproducibility. The average latency of these components was significantly delayed by 9.8 ms for N75 and 10.2 ms for P100, and the N75-P100 amplitude was significantly larger than the conventional p-VEP elicited by the CRT screen. During the reversal phase, especially from black-to-white, the luminance of the LCD screen was transiently reduced, and it elicited a flash VEP and ERG. A reduction in the contrast of the checks minimized the transient change in the luminance, and the VEP waveform was more similar to that elicited by the CRT screen.
  
  
  CONCLUSIONS
  The results suggest that when an LCD monitor is used as an alternative visual stimulator to elicit p-VEPs, the delay in the luminance change and the flash effect needs to be taken into account.
authors.affiliation: Department of Ophthalmology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo, 173-8605, Japan.
authors.forename: Celso Soiti
authors.initials: CS
authors.lastname: Matsumoto
authors.forename: Kei
authors.initials: K
authors.lastname: Shinoda
authors.forename: Harue
authors.initials: H
authors.lastname: Matsumoto
authors.forename: Hideaki
authors.initials: H
authors.lastname: Funada
authors.forename: Haruka
authors.initials: H
authors.lastname: Minoda
authors.forename: Atsushi
authors.initials: A
authors.lastname: Mizota
mesh_terms: D000328:Adult; D055984:Cathode Ray Tube; D003626:Data Display; D004596:Electroretinography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D050866:Liquid Crystals; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000295:instrumentation*; D011930:Reaction Time / Q000502:physiology; D015203:Reproducibility of Results; D055815:Young Adult