Eyetracker Outcomes in a Randomized Trial of 40 Sessions of Hyperbaric Oxygen or Sham in Participants with Persistent Post Concussive Symptoms
Eye movements may offer a sensitive method to detect abnormalities and measure response to intervention in mild traumatic brain injury (mTBI).
The Brain Injury and Mechanisms of Action of Hyperbaric Oxygen for Persistent PostConcussive symptoms after Mild Traumatic Brain Injury Study (BIMA) randomized 71 participants to either 40 daily sessions of hyperbaric oxygen or sham. A companion normative population study enrolled 75 participants. An eye-tracking system (EyeLink II, SR Research, Ottawa, Canada) was used to measure eye movements at baseline, 13 weeks and six months. Left and right eye movements were recorded for up to 34 parameters for 11 tracking tasks including both saccadic and smooth pursuit. Results were considered significant if t-tests for at least one eye was significant at P<0.001 and the contralateral eye at P<0.02 as confirmatory evidence to adjust for multiple testing.
Of the 34 test parameters measured, all but five during the circular task, four during the horizontal ramp task, and 13 during the reading task showed significantly worse performance in the BIMA population compared to the normal population. On average, BIMA participants read fewer lines than normative participants (44.3 vs. 47.8 lines, P=0.04), averaged more fixations (6.9 vs. 6.1, P=0.004) and more regressions per line (3.8 vs. 3.1, P=0.0002). At 13 weeks and six months, BIMA participants shifted toward the normal population distribution for the circular and horizontal ramp tasks. The reading task continued to suggest abnormalities, with no differences between the hyperbaric and sham arms.
Circular, horizontal ramp, and reading tasks were the most sensitive in differentiating between the normative and BIMA participants, suggesting potentially greater vulnerability of the smooth pursuit system to mTBI compared to the saccadic system. Hyperbaric oxygen did not result in a significant improvement compared to sham.