Multiple factors contribute to pupillary light reflex: implications for screening of traumatic brain injury in...

This study aimed to assess the contribution of demographics, medical history, and psychological health to pupillary light reflex (PLR) indices in Service members with and without a history of mild traumatic brain injury (mTBI).

PLR data from NeurOptics NPi-300 were analyzed on 216 participants who were categorized as non-injured controls (NIC), mTBI with no loss of consciousness (mTBI^LOC-), or mTBI with LOC (mTBI^LOC+). Multiple independent regression models were conducted for each PLR index to assess the contribution of these factors to the variability of PLR indices by group.

There were no significant group differences on the PLR indices. Age was a significant factor across groups, but more robust for those with mTBI. Sleep duration, injury characteristics, and psychological health effects on PLR indices were primarily observed in the mTBI^LOC+ group. Posttraumatic stress and sex were not significant predictors in any of the models.

When using PLR for screening of mTBI, an individual's age, history of prior mTBI, total lifetime TBI-related alterations in consciousness, sleep, and anxiety and depression symptoms should be considered when interpreting PLR metrics.

Controlling for these factors is essential for validating the use of PLR for screening of mTBI.