The Effect of Optotype Size and Velocity Parameters on the Performance of Healthy Young Adult Subjects on the Gaze Stabilization Test

Abstract

The purpose of the current study was to examine the influence of the optotype (the letter E) size, presentation time, and head velocity on gaze stabilization test (GST) performance. The gaze stabilization test is a functional measure of the vestibulo-ocular reflex. Twenty-one healthy young subjects (mean age, 26 ± 4; range, 21-34, 10 male subjects) performed the computerized GST. Testing was repeated several times using different combinations of the optotype size and presentation time over a wide range of head velocities (<60 to >220 degrees per second). The sizes examined were 0.20, 0.25, and 0.30 logMAR above the subject's static visual acuity (SVA). The presentation times examined were 20, 30, and 40 ms above the subject's minimum perception time (mPT). Performance varied considerably based on the optotype parameters used in the GST. The optotype combination of SVA + 0.20 logMAR and mPT + 20 ms was the most difficult combination with the average of all subjects' performance less than 64% at all velocities. The optotype combination SVA + 0.30 logMAR and mPT + 40 ms was the easiest combination with subjects being able to correctly identify the optotype at any head velocity with greater than 70% average accuracy. Increasing the head velocity in any size/time combination caused deterioration in subjects' performance. Our study findings show that optotype parameters have significant influence on subjects' performance on the GST.