Analysis of Eye Movements during Monocular and Binocular Fixation*

Abstract

Recordings of the horizontal component of movements of the eyes were made during monocular and binocular fixation. The variation in the vergence of the eyes over time was found to be of the same order of magnitude as the variation in position of the individual eyes, even though the lateral positions of the two eyes are somewhat correlated. The drift and tremor of the two eyes are not correlated; the over-all correlation is due to the saccadic movements. Saccades in one eye seem to be always accompanied by simultaneous saccades in the other eye which are almost always in the same direction and about the same in size. The maintenance of binocular fixation does not seem to be dependent on a direct response to or sensing of vergence error. Rather, it appears to be dependent on the saccadic responses of the two eyes to their own fixation errors.