Observer‐perceived light aversion behaviour in photophobic subjects with traumatic brain injury

Abstract

Background

Photophobia is a common sequela of traumatic brain injury (TBI). Diagnostic tools for this debilitating condition are lacking. This investigation sought to determine whether masked observers can distinguish subjects with TBI‐associated photophobia from matched controls based on video recordings of their ocular responses to light stimulation.

Methods

Cohorts of students (n = 20), photophobic TBI subjects (n = 28) and their matched control subjects (n = 12) were recruited. A custom pupillometer delivered bright (10¹³–10¹⁴ photons/s/cm²), flashing (0.10-Hz) red (625-nm) and blue (470-nm) light stimuli to subjects, and consensual pupil light responses were recorded. Using a five‐point scale, masked observers later graded light aversion behaviour in the pupil video recordings obtained from the student cohort based on observed blinking, tearing and squinting. A grading scale was developed and used by masked observers to grade light aversion behaviour in videos obtained from subjects with post‐TBI photophobia and the matched controls. These subjects also scored their perceived discomfort during each light pulse using a five‐point scale.

Results

The subjects in the TBI cohort scored both the blue and red flashing stimuli as evoking more discomfort, relative to control subjects, consistent with their reported photophobia. There was strong agreement among the masked observers for their grades of light aversion behaviour in the videos of ocular light stimulation (interclass correlation co‐efficient = 0.78; 29 per cent perfect concordance). However, the median grades for the videos obtained from the TBI subject cohort were not significantly different from those for the control group.

Conclusions

Clinicians cannot diagnose TBI‐related photophobia based solely on video recordings of ocular responses to light. The need remains for an objective test to diagnose and manage this prevalent post‐TBI symptom.

Key words:

• photophobia
• pupil
• retinal ganglion cells
• traumatic brain injury

ACKNOWLEDGEMENTS

NIH Loan Repayment Program L30 EY024749, National Center For Advancing Translational Sciences Grant 8KL2TR000112‐05 and the Department of Defense TATRC Grant W81XWH‐12‐1‐0434.

Supporting information

Additional supporting information may be found in the online version of this article at the publisher’s website: http://onlinelibrary.wiley.com/doi//suppinfo.

Appendix S1. Pupillary light responses.

Figure S1. Pupil responses to flashes of red or blue light.

Figure S2. Representative images from the standardised videos described in Table 2.

Additional information

Funding

National Center for Advancing Translational Sciences

US Department of Defense TATRC

National Center For Advancing Translational Sciences

National Institutes of Health Division of Loan Repayment