title: Low luminance/eyes closed and monochromatic stimulations reduce variability of flash visual evoked potential latency.
abstract: BACKGROUND
  Visual evoked potentials are useful in investigating the physiology and pathophysiology of the human visual system. Flash visual evoked potential (FVEP), though technically easier, has less clinical utility because it shows great variations in both latency and amplitude for normal subjects.
  
  
  OBJECTIVE
  To study the effect of eye closure, low luminance, and monochromatic stimulation on the variability of FVEPs.
  
  
  METHODS
  Subjects in self-reported good health in the age group of 18-30 years were divided into three groups. All participants underwent FVEP recording with eyes open and with white light at 0.6 J luminance (standard technique). Next recording was done in group 1 with closed eyes, group 2 with 1.2 and 20 J luminance, and group 3 with red and blue lights, while keeping all the other parameters constant. Two trials were given for each eye, for each technique. The same procedure was repeated at the same clock time on the following day.
  
  
  METHODS
  Variation in FVEP latencies between the individuals (interindividual variability) and the variations within the same individual for four trials (intraindividual variability) were assessed using coefficient of variance (COV). The technique with lower COV was considered the better method.
  
  
  RESULTS
  Recording done with closed eyes, 0.6 J luminance, and monochromatic light (blue > red) showed lower interindividual and intraindividual variability in P2 and N2 as compared to standard techniques.
  
  
  CONCLUSIONS
  Low luminance flash stimulations and monochromatic light will reduce FVEP latency variability and may be clinically useful modifications of FVEP recording technique.
authors: Department of Physiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India.
authors: Senthil Kumar
authors: SK
authors: Subramanian
authors: Giriwar Singh
authors: GS
authors: Gaur
authors: Sunil K
authors: SK
authors: Narayan
keywords: Eye closure; flash visual evoked potentials; latency variability; luminance; monochromatic light; visual evoked potentials