Photophobia is a common symptom in individuals suffering from traumatic brain injury (TBI). Recent evidence has implicated blue light-sensitive intrinsically photosensitive retinal ganglion cells (ipRGCs) in contributing to the neural circuitry mediating photophobia in migraine sufferers. The goal of this work is to test the hypothesis that ipRGC function is altered in TBI patients with photophobia by assessing pupillary responses to blue and red light.
Twenty-four case participants (mean age 43.3; 58% female), with mild TBI and self-reported photophobia, and 12 control participants (mean age 42.6; 58% female) were in this study. After 10 minutes of dark adaptation, blue (470 nm, 1 × 1013 phots/s/cm2) and red (625 nm, 7 × 1013 phots/s/cm2) flashing (0.1 Hz) light stimuli were delivered for 30 seconds to the dilated left eye while the right pupil was recorded. The amplitude of normalized pupil fluctuation (constriction and dilation) was quantified using Fourier fast transforms.