Gaze stabilization test: reliability, response stability, performance of healthy subjects and patients with concussion

Gaze stabilization test (GST) and dynamic visual acuity (DVA) test are functional measures of the vestibulo-ocular reflex which helps to maintain clear vision during head movement. The purposes of this dissertation were threefold; first the reliability of GST and DVA test were examined. Twenty-nine patients with vestibular disease were tested repeatedly using the computerized InVision™ test. Results showed that the reliability of the tests were fair to poor with the DVA reliability better than the GST and the within-session reliability better than between-session reliability. In the second Aim, the goal was to obtain better understanding of the effect of optotype (the letter E) parameters on subjects' performance. The performance of twenty-one healthy young subjects on the GST was examined over a range of optotype sizes and presentation times. Results showed that the optotype parameters had a significant effect on subjects' performance with only one combination in which most healthy subjects were able to accomplish fast head velocities while being able to identify the optotype correctly. An optotype that is 0.30 logMAR above a subject's static vision and presented for 40 msec longer than minimum presentation time is recommended for future testing. Lastly, the preferred combination from the second Aim was used to examine the performance of twenty-two young patients following concussion and compare it with the healthy subjects from Aim 2. Correlations between patients' performance on the GST and their scores on tests commonly used following concussion were also examined. Results showed no significant differences between the performance of patients and that of healthy subjects on the GST. Also, there were no significant correlations between the GST and other measures used following concussion. Results show that the protocol used for the GST needed refinement. Special consideration is to be given to the optotype parameters used since these were found to significantly influence performance. The lack of significant differences between patients following concussion and healthy subjects could be due to the inclusion of all patients following concussion without objective evidence of vestibular involvement. Future studies should use specific optotype parameters and include patients following concussion with evidence of vestibular dysfunction