Fig. 10. The standing potential of the eye. For purposes of the electro-oculogram, the eye may be thought of as a battery. The anterior part has a positive polarity relative to the posterior part of the eye. As the eye shifts in position from side to side over a 30-degree excursion, skin electrodes record electrical changes; these can be amplified and recorded on a computer and displayed on an ink writer or cathode ray oscilloscope. (Adapted from a video frame obtained from Metrovision, Pérenchies, France: