Eye tracker outcomes in a randomized trial of 40 sessions of hyperbaric oxygen or sham in participants with persistent post concussive symptoms

Purpose: Eye movements may offer a sensitive method to measure response to intervention in mild traumatic brain injury (mTBI). Methods: The Brain Injury and Mechanisms of Action of Hyperbaric Oxygen for Persistent Post-Concussive Symptoms after Mild Traumatic Brain Injury Study (BIMA) randomized 71 participants to 40 sessions of hyperbaric oxygen or sham. A companion normative study (Normal) enrolled 75 participants. An eye tracking system measured left and right eye movements for saccadic and smooth pursuit. At baseline two smooth pursuit tasks, circular and horizontal ramp, and four saccadic tasks, horizontal and vertical step, reading, and memory guided-on tasks differentiated BIMA from Normal participants. The change from baseline in these tasks were measured and compared between interventions and against Normal participants at 13 weeks and six-month follow-up using the two-sample t-test. The Holm-Bonferroni procedure was used to adjust for multiple testing. Results: Change from baseline in eyetracker measures for participants assigned to the hyperbaric oxygen arm did not significantly differ from those assigned to the sham arm at post-randomization time points 13 weeks and six months. Consistent shifts of BIMA participant values toward Normal values at 13 weeks and six months were observed for overall fixation duration, forward saccadic duration, and number of lines read for the reading task, number of misses on the memory guided-on task, and absolute intersaccadic interval velocity and absolute saccadic amplitude on the circular task. The distributions between Normal and BIMA participants were no longer statistically significantly different at 13 weeks and six months post enrollment for these measures. Conclusions: The baseline differences between BIMA and Normal suggest potential vulnerability of the smooth pursuit system and the saccadic system. During the sixmonth follow-up period, improvement toward Normal was seen on some measures in both the hyperbaric oxygen and sham intervention arms without difference between intervention groups. clinicaltrials.gov Identifiers NCT01611194 and NCT01925963