Poster Session I: Characteristics and coordination of microsaccades in 6 Dimensions.

Abstract

The study of microsaccades, the small and rapid eye movements that occur during fixation, has focused on horizontal and vertical movements, while their torsional component remains relatively uncharted territory in vision research. We used video eye tracking to investigate microsaccades binocularly with horizontal and vertical movements tracked by pupil and corneal reflection and torsion by iris pattern. Five participants looked at a central dot for 20 trials of 20 seconds while seated, and their heads rested on a chin rest. For each microsaccade (N=2040), we measured the displacement of the eye along each dimension, and defined version as the average and vergence as the difference between the motion of the left and right eye. The average horizontal vertical and torsional components were 0.7, 0.3, and 0.1 deg for version and 0.1, 0.1, and 0.1 deg for vergence, respectively. Next, we measured the correlation between each component pair. We found that when the eyes moved to the left or right together, they also rotated by 0.3 deg (top towards the same side) for each degree of horizontal movement (R = 0.94, p < 0.01). When the eyes moved up (down), for each degree of vertical movement, they diverged (converged) 0.08 deg horizontally (R = -0.53, p < 0.01) and rotated 0.09 deg outward (inward; R = -0.47, p < 0.01). There was no strong correlation between other combinations. These results show that microsaccades follow similar kinematics at a minute scale as larger saccades.