The Human Eye Position Control System in a Rehabilitation Setting

• Main Authors: Yvonne Nolan, Edward Burke, Clare Boylan, Annraoi de Paor
• Format: Article
• Language: English
• Published: VSB-Technical University of Ostrava 2005-01-01
• Series: Advances in Electrical and Electronic Engineering
• Subjects: eye position; rehabilitation; control system.
• Online Access: http://advances.utc.sk/index.php/AEEE/article/view/244

Our work at Ireland’s National Rehabilitation Hospital involves designing communication systems for people suffering from profound physical disabilities. One such system uses the electro-oculogram, which is an (x,y) system of voltages picked up by pairs of electrodes placed, respectively, above and below and on either side of the eyes. The eyeball has a dc polarisation between cornea and back, arising from the photoreceptor rods and cones in the retina. As the eye rotates, the varying voltages projected onto the electrodes drive a cursor over a mimic keyboard on a computer screen. Symbols are selected with a switching action derived, for example, from a blink. Experience in using this mode of communication has given us limited facilities to study the eye position control system. We present here a resulting new feedback model for rotation in either the vertical or the horizontal plane, which involves the eyeball controlled by an agonist-antagonist muscle pair, modelled by a single equivalent bidirectional muscle with torque falling off linearly with angular velocity. We have incorporated muscle spindles and have tuned them by pole assignment associated with an optimum stability criterion.<br />