An EOG records eye movement by detecting a voltage difference between the cornea and retina. As the eye moves, the vector of this electric field changes with respect to recording electrodes placed in the skin at fixed points. These bioelectrical signals are typically very small in amplitude (µV) and an amplifier is required to accurately record the EOG.
Slow-tracking eye movements occur at 3-40 Hz (a feature used in humans to track distant moving objects and slow moving near objects). The tracking movements of the eye become rapid (900 Hz) and the eye moves back and forth very quickly when the object is moving rapidly.