June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
The photopic negative response in mild traumatic brain injury
Author Affiliations & Notes
  • Roa Al-Abdalla
    Vision Science, SUNY College of Optometry, New York, New York, United States
  • Nabin Joshi
    Vision Science, SUNY College of Optometry, New York, New York, United States
  • Jennifer Nguyen
    Vision Science, SUNY College of Optometry, New York, New York, United States
  • Kenneth J Ciuffreda
    Vision Science, SUNY College of Optometry, New York, New York, United States
  • Suresh Viswanathan
    Vision Science, SUNY College of Optometry, New York, New York, United States
  • Footnotes
    Commercial Relationships   Roa Al-Abdalla, None; Nabin Joshi, None; Jennifer Nguyen, None; Kenneth Ciuffreda, None; Suresh Viswanathan, None
  • Footnotes
    Support  T35EY020481 SUNY College of Optometry
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 4281. doi:
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    • Get Citation

      Roa Al-Abdalla, Nabin Joshi, Jennifer Nguyen, Kenneth J Ciuffreda, Suresh Viswanathan; The photopic negative response in mild traumatic brain injury. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4281.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The photopic negative response (PhNR) is a slow negative potential of retinal ganglion cell origin in the cone-mediated flash electroretinogram (ERG). The purpose of this study was to examine whether the PhNR is altered in patients with a diagnosis of mild traumatic brain injury (mTBI).

Methods : PhNRs were recorded using DTL fiber electrodes with a Ganzfeld System (Diagnosys LLC) from 9 patients with mTBI (22-45 years of age) and 21 control subjects (22-49 years of age). Stimuli consisted of brief (<5 ms) red flashes ranging from -2.2 to 0.8 log phot cd.s/m2 on a 2 log scot cd/ m2 blue background. The PhNR amplitude was measured at its trough from baseline and the b-wave, which originates from cone bipolar cell activity, was measured at its peak from the preceding a-wave. Both the PhNR and b-wave amplitudes were plotted as a function of flash intensity and fitted with the Naka-Rushton equation, V(I) = (Vmax*In)/(In+Kn), where V is the response at intensity I, Vmax is the saturated amplitude, n is the slope and K is the semi-saturation constant (intensity at 50% of Vmax). Vmax, n and K derived from the fits were compared between mTBI patients and controls.

Results : For the PhNR intensity response function, n was significantly larger (p=0.03) and K was significantly smaller (p=0.036) in the mTBI group (n=1.6, K=0.13) relative to the control group (n=0.99, K=0.20). K also showed a significant negative correlation with n (r=0.18, m=-0.16, p<0.001). The Vmax of the PhNR and all Naka-Rushton fit parameters of the b-wave were not significantly different between mTBI patients and control subjects.

Conclusions : A selective increase in the slope of the PhNR intensity response function of mTBI patients with a corresponding decrease in the semi-saturation constant indicates elevated sensitivity of the cellular generators of the PhNR in patients with mTBI. This finding may suggest a potential pre-cortical basis for photosensitivity in mTBI.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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