Two-year retest stability of eye tracking performance and a comparison of electro-oculographic and infrared recording techniques: evidence of EEG in the electro-oculogram.

This study assessed the quantitative and qualitative comparability of simultaneously recorded electrooculographic (EOG) and infrared (IR) measures of eye movement and the long-term retest stability of the EOG. Fifty-two twins, all of whom performed the same tasks while the EOG was recorded two years ago, engaged in smooth-pursuit tracking of sinusoidally driven targets ranging in frequency from. 4 to 1.2 Hz and in saccadic tracking of a modified square wave target. In addition to computer-derived estimates of smooth-pursuit and saccadic eye tracking proficiency, a measure of saccadic interference during smooth-pursuit tracking and ratings of the amount of small-amplitude spiky oscillation in the EOG were made. Two-year retest stability of these various measures varied from .54 to .83 and were similar to within-session and one-week retest reliabilities computed for these same subjects. Correlations between computer-derived EOG and IR scores ranged from.89 to.99 indicating good correspondence between the two methods. Qualitative EOG-IR comparability was not high for subjects who showed a pronounced spiky oscillation in the EOG. Spectral analyses of the EOG and concurrently recorded EEG suggest that this spiky rhythm represents EEG (perhaps kappa or alpha), the presence of which is correlated with poor eye tracking.