Vertical Fusional Response to Asymmetric Disparities

Objective measurement of the human vertical fusional response to asymmetric disparity presentation was carried out. Ramp disparities evoked mostly monocular eye movements. Step disparities evoked binocular eye movements which began with conjugate saccades followed by slower vergence movements. The two saccade amplitudes were approximately equal, and each was greater than half of the disparity. Motor compensation was mostly incomplete, allowing for the existence of a significant sensory component. Slower time course characterized the vertical vergence movements which were otherwise similar to the horizontal motor response to asymmetric disparity presentation.