Since man depends on his visual sense more than on his other senses, the ability to direct the eyes accurately toward an object of interest is very important. To accomplish this task, volitional, reflex, and vestibular commands all converge on gaze centers in the brainstem. Processing and integration of these commands results in stimulation of the appropriate ocular motor nuclei and inhibition of the nuclei of the opposing muscles. In addition, the speed and amplitude of the movement in both eyes must match each other and the target position. The final task is to hold the eyes in an eccentric position, resisting the elastic forces in the orbit, to maintain fixation.
A sophisticated system exists to accomplish these movements. The advent of eye-movement recording and computer analysis have given us a better understanding of the anatomic and physiologic mechanisms of gaze. Most clinicians, however, do not have easy access to an eye-movement laboratory for help in diagnosing gaze disorders. Therefore, in this chapter I emphasize the correlation of clinical gaze abnormalities with anatomic lesions. Gaze palsies do not have specific causes. Indeed, any category of disease that can affect the nervous system can potentially cause a gaze palsy.