Walsh & Hoyt: Six Eye Movement Systems and Their Two Goals

Eye movements are divided into different types called systems, each of which performs a specific, quantifiable function and has a distinctive anatomic substrate and physiologic organization. We can best understand the types of eye movements when we consider the major goals of the ocular motor systems. There are six systems: saccadic, smooth pursuit, fixation, vergence, vestibulo-ocular, and optokinetic. All six systems interact during visual tasks. They have two goals: attaining fixation with both eyes, and preventing slippage of images on the retina. The saccadic system uses fast eye movements to attain fixation of images that lie off the fovea, whereas the other systems generate slower smooth eye movements to maintain fixation and prevent image slip on the retina.