Supranuclear Disorders of Ocular Motility

Abstract

There are several different types of eye movements coordinated with one another and regulated by an integrated control system. Refixation saccadic movements serve to redirect the eye, to bring images of interest to the center of the retina. Pursuit movements and optokinetic nystagmus prevent or reduce slippage of the image over the retina. The vestibulo-ocular reflex acts to stabilize the eye’s position during head movements. Convergence and divergence movements allow objects at various distances to be imaged on the retinas at corresponding locations. The various types of movement are classified in ■ Fig. 11.1. Supranuclear structures that act through the motor nuclei of the third, fourth, and sixth cranial nerves have the task of coordinating the movements of both eyes, on the one hand, and on the other hand, they must generate the encoded innervational signal patterns for each of the various types of eye movement. The innervational signals are integrated within the cells of the motor nuclei. Consequently, infranuclear (peripheral) lesions compromise the final common pathway – all the eye movement types summarized in ■ Fig. 11.1 – whereas supranuclear lesions can cause separate impairments of individual types of eye movement. Supranuclear Disorders of Ocular Motility