Abstract
Introduction. Spectral analysis of electroretinographic (ERG) responses provides a non-invasive probe for the functioning of a broad range of receptor and inner retinal mechanisms the in human eye. We investigated the visual and ERG characteristics in a sample of sufferers of traumatic brain injury (TBI) with and without hypersensiivity to light (photalgia). Methods. We recorded light-adapted electroretinograms (ERG) from facial electrodes. High-quality ERG responses for full-field stimulation as a function of wavelength and intensity were obtainable for whole-field chromatic R (610 nm), G (540 nm), B (480 nm) and W (R + G + B) stimulation with 2.5 Hz square-wave modulation (200 ms on/ 200 ms off) at a maximum intensity of 265 cd/m2 (W). Signals were recorded from a population of individuals with varying degrees of photalgia due to mild traumatic brain injury, and controls. Photalgic participants used a staircase procedure to set each stimulus to the highest tolerable intensity. Results. Light-adapted ERGs in controls exhibited similar properties to dark-adapted ERGs, with the a-wave peak at about 20 ms, the b-wave peak at about ~40 ms and the photopic negative response (PhNR) at about 80 ms, consistent with an origin in the cone pathways. The 660 nm condition reveals a striking second peak in the b-wave known as the x-wave, which may derive from rod responses but seems to be masked by the PhNR at other wavelengths. These functional properties were significantly altered across the TBI population, with marked attenuation and delayed b-wave peaks and loss of the PhNR after taking into account the requisite intensity reductions, especially in those with photalgia. These abnormal features could be interpreted as profound reductions in the cone signal contributions to the ERG. Conclusion. The ERG changes in the TBI patients potentially provide the first objective biomarker for retinal effects of TBI.
Meeting abstract presented at VSS 2017