Abstract
Purpose :
Saccadic eye movement parameters have been studied as an objective measure of neurological function and impairment in concussion. Significant differences between latency, velocity and accuracy often rely upon the analysis of a group of saccades including those in both rightward and leftward directions. Should rightward and leftward saccades of the same magnitude be treated differently? Some studies have found a relationship between eye and hand dominancy and rightward-leftward saccade peak velocity asymmetry. The purpose of this study is to assess the symmetry of rightward and leftward saccade peak velocity in normal control subjects and in those with post-concussion syndrome.
Methods :
Using a gap saccade paradigm, 720 randomly ordered horizontal saccades of 5, 10, 15 and 20 degrees were recorded using an ISCAN eye tracker. Saccade peak velocity in degrees/second is assessed in a sample of 90 rightward and 90 leftward 20-degree saccades from 5 normal controls and 3 subjects with post-concussion syndrome. For each lateral saccade a cyclopean measure is generated by averaging the paired right eye and left eye saccade peak velocities. Cyclopean rightward and leftward saccade peak velocities are evaluated for significant differences and calibration precision is assessed in each subject.
Results :
Paired-samples t-tests from 90 20-degree rightward and 90 20-degree leftward saccade peak velocities indicate that 2 control subjects (1.Mean R-202 & L-221, SD R-28, & L-27, p=.001 and 2.Mean R-346 & L-276, SD-R42, & L-31, p=.000) exhibit significant rightward-leftward asymmetry. The remaining 6 subjects show no significant difference between mean values of rightward and leftward saccade peak velocities (p=.157-.934, CI=95%). Calibration data is suboptimal in the 2 control subjects who exhibited significant right-left asymmetry.
Conclusions :
In a cyclopean saccade testing paradigm, rightward and leftward saccade peak velocities are comparable. Right–left asymmetry of saccade peak velocity is not correlated to post-concussion syndrome status. Data from rightward and leftward saccade peak velocities are equivalent and can be pooled in individual subjects provided that optimal calibration is assured.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.