Types of movements

We now consider movements based on their purpose, resulting in six categories: 1) saccades, 2) smooth pursuit, 3) vestibulo-ocular reflex, 4) optokinetic reflex, 5) vergence, and 6) microsaccades. All of these motions cause both eyes to rotate approximately the same way, except for vergence, which causes the eyes to rotate in opposite directions. We will skip a seventh category of motion, called rapid eye movements (REMs), because they only occur while we are sleeping and therefore do not contribute to a VR experience. The remaining six categories will now be discussed in detail.