The influence of genetic factors on smooth-pursuit and saccadic eye tracking was determined using 34 pairs of monozygotic and 24 pairs of dizygotic twins. Subjects engaged in smooth-pursuit tracking of different-frequency sinusoidal targets and saccadic tracking of an abruptly moving, rectangular-wave target. Tracking error and phase lag served as dependent measures for the pursuit tasks; saccadic eye tracking performance was evaluated by measuring oculomotor reaction times. The results suggest a genetic basis for smooth-pursuit tracking error; the intraclass correlations for performance averaged over all pursuit tasks were 0.68 and 0.35 for the identical and fraternal twins, respectively. While equivocal results were found for the phase lag data, there was no evidence for the influence of genetic factors on oculomotor response times. These findings are in agreement with the results of twin studies using psychiatric patients.
- eye tracking
- saccadic eye movement latency
- smooth-pursuit eye movements