title: Effect of luminance on the visually-evoked potential in visually-normal individuals and in mTBI/concussion.
abstract: OBJECTIVE
  To assess quantitatively the effect of luminance on VEP amplitude and latency in visually-normals (VN) and patients with mild traumatic brain injury (mTBI).
  
  
  METHODS
  VN individuals (n = 20) and those with mTBI (n = 19) participated. Those with mTBI were assessed 1-10 years post-injury (mean = 4.97 years), with the exception of one subject. Pattern VEP testing was employed using the DIOPSYS™ NOVA-TR system, with a 74 cd m-2baseline luminance. Luminance levels were reduced with five different neutral density (ND) filters (0.5, 1.0, 1.5, 2.0 and 2.5) and compared to the baseline response. All testing was performed under binocular-viewing conditions with full refractive correction in place.
  
  
  RESULTS
  In both groups, mean VEP amplitude reduced with decrease in luminance (p < 0.05). At each luminance level, the mean VEP amplitude was significantly lower in mTBI than in the VN population (p < 0.05). In both groups, the mean VEP latency increased progressively with reduction in luminance (p < 0.05), with it being significantly higher in mTBI than in the VN population (p < 0.05).
  
  
  CONCLUSIONS
  High luminance levels produced an optimal VEP response in both populations. VEP amplitude was robust, whereas latency progressively increased in both groups as luminance decreased. The latency increase with decreased luminance was significantly larger in those with mTBI, thus suggesting that latency can be used to differentiate reliably between VN individuals and those with mTBI.
authors.affiliation: a Department of Biological and Vision Sciences , SUNY/State College of Optometry , New York , NY , USA.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Fimreite
authors.affiliation: a Department of Biological and Vision Sciences , SUNY/State College of Optometry , New York , NY , USA.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Ciuffreda
authors.affiliation: a Department of Biological and Vision Sciences , SUNY/State College of Optometry , New York , NY , USA.
authors.forename: Naveen K
authors.initials: NK
authors.lastname: Yadav
keywords: Amplitude; VEP; latency; luminance; magnocellular pathway; mild traumatic brain injury (mTBI); objective biomarker; visually-evoked potential