We developed a method for rehabilitating eye movements and binocular fusion, and tested the method in one patient. An infarct of the pons caused the paresis of the lateral rectus muscle of the left eye. Beginning from the third week in hospital, the patient was trained in eye movements and binocular fusion. Fusion was made possible by means of prisms that moved the images of targets in central vision to the threshold of fusion in the primary eye position. During practice sessions lasting 0.5 to 2 h daily the patient kept the images fused by making a horizontal head movement when necessary. Several eye-movement sessions were held daily, consisting of voluntary saccades and fixations as far to the left as possible. The strength of the prismatic correction required for fusion decreased, and four months after the onset of stroke the patient could fuse without prisms in the primary position. His binocular vision became practically normal in one year. The plasticity of the visual system can be utilised in rehabilitation by a practice that uses minimal remedial means necessary for correct function at each level of performance.
Binocular fusion and invariant category learning due to predictive remapping during scanning of a depthful scene with eye movements