Gaze-contingent prism adaptation: Optical and motor factors.

Abstract

Vision can adapt for some optical distortions that vary with the direction of gaze, in particular for the variable image stretching and shearing caused by prism spectacles. These 2 adaptations were studied using both vertically and horizontally oriented adaptation prisms, thereby untying the type of image distortion from the type of correlated eye movement. Experiment I showed the mechanisms of the 2 adapta-tions to differ, the shearing adaptation being critically dependent on the orientation of the correlated eye movements. In Experiment n, the shearing adaptation was found not to be the exact complement of the optical shearing: the apparent tilting of some image lines was reduced (positive adaptation), while the apparent countertlltlng of other image lines was increased (negative adaptation). It was concluded that the adaptation to prismatic image shearing is a rotation, most probably a change in the patterning and registration of torsional eye movements.