The diagnostic value of abnormal eye movements: A pathophysiological approach

Eye movements are necessary to ensure optimal vision of the environment. To see clearly, images of the seen world must be held steady on the retina. If images move across the retina at more than a few degrees per second, they appear blurred. Therefore, one function of eye movements is to stop images from moving on the retina; this is done by vestibular and optokinetic eye movements. Visual acuity is best at the fovea, so a second function of eye movements is to change the line of sight so that images of objects of interest are brought to and kept on the fovea; this is performed by saccadic, pursuit and vergence movements. The clinician who can systematically test each functional class of eye movements, and who knows the underlying anatomy and physiology, can better identify the nature and location of many neurological disease processes.