Understanding Gaze Control Mechanisms in Healthy Individuals versus Individuals with Multiple Sclerosis

Overview

Multiple sclerosis (MS) is the most common non-traumatic neurological disease in both North America and Europe. People with multiple sclerosis (PwMS) experience debilitating symptoms such as dizziness and balance deficits. Previous literature indicates tha t the vestibulo -ocular reflex (VOR) has correlation with dizziness when it is not functioning properly, due to its role in gaze stabilization. For the procedure, two tests were performed that are common in vestibular research, video head impulse testing (v HIT) and computerized dynamic visual acuity (cDVA). vHIT consists of abrupt head thrusts while participants attempt to keep their visual field fixed on a static point, this test will generate metrics for VOR gain (eye velocity/head velocity), gaze position error (GPE [eye position vs. head position]), and saccade latency (amount of time for the first saccade to generate). For cDVA, participants attempted to identify different letters, first while their heads were stationary, and secondly with a self -generated head rotation. In VOR gain, we saw significant differences in gain metrics, but saw greater decreases on the vertical planes of motion than horizontal planes. This suggests that PwMS have worse function in the pitch plane than the yaw plane. Additionally, we saw that during vHIT, participants with MS would still be off target by approximately half a degree at the 400 millisecond mark. cDVA results indicated that MS has little effect on this test. This suggests that rehabilitation programs for PwMS should focus more on pitch movements than yaw movements, seeing as their pitch results were considered abnormal.