Changes in the electro-oculogram potential level.

THE eyeball may be regarded as a small battery, with a positive pole in the cornea and a negative pole in the retina. The work of Fenn and Hursh (1937), Frangois, Verriest, and de Rouck (1957), and others, suggests that the corneo-retinal potential is associated primarily with the retinal receptors; Brindley (1956) has suggested that the resting potential of the lens may contribute to it, and it may be that the cornea also contributes. Changes in the position of the eyeball cause changes in potential at the skin surface round the eye socket; these changes can be detected, amplified, and measured by the technique known as electro-oculography (EOG). The changes of potential are, for practical purposes, linearly related to the angle of the eyeball rotation and have been used as measures of eye movement and eye position. Conversely, by having the subject make known angular rotations of the eyeball, the potential changes can be recorded under standard conditions to give the "EOG potential level". Provided that the measurement conditions are standardized and that the body structure surrounding the eyeball is a relatively homogeneous conducting medium, at least in the plane of movement, the "EOG potential level" may be considered as a direct function of, and therefore as a measure of, the potential difference between cornea and retina. The following definitions have therefore been suggested (Shackel, 1960):