Figure 2.

Schematic of geometry of the linear or translational vestibulo-ocular reflex (T-VOR). During vertical head translations (in the Z-axis, bob or heave), vertical eye rotations are required to hold the eyes on target. The magnitude (θ) of eye movements required to hold the foveal line of sight on the target is given by the equation at bottom, where D is the target distance and A is the amplitude of the head translation. Note that during fixation on a near target (lower panel), larger eye rotations are required than while viewing far objects (upper panel). This geometry indicates that the T-VOR cannot generate eye rotations that simultaneously hold images of far and near targets still on the retina.