1. A method for controlling the position of an image on a video display, comprising the steps of: (a) sensing electro-oculogram voltage signals representing the horizontal position of a right eye in relation to a first reference point; (b) sensing electro-oculogram voltage signals representing the horizontal position of a left eye in relation to said first reference point; (c) determining the numerical difference between said electro-oculogram voltage signals representing the horizontal position of said right eye and said electro-oculogram signals representing the horizontal position of said left eye; (d) successively repeating step (c); (e) controlling the position of an image on a video display based on a change in the amplitude of the electro-oculogram signals derived in step (d).