Independent monocular eye position control through biofeedback

Three subjects with normal binocular vision and one constant exotrope attempted to gain independent control of eye position through biofeedback. Eye position was monitored by the voltage Induced in a contact lens coil as a function of its orientation within an alternating magnetic field. Visual feedback of eye position was displayed on an oscilloscope screen. The contact lens used in the system could not be tolerated by the exotropic subject and hence, he was dropped from the study. Each of the three normal subjects were able to achieve a strabismic posture (esotropia and exotropia) by a unilateral adduction or abduction. Phorias were monitored in one subject during and after the attempted exotropic deviation and an increase in exophoria was observed. The magnitude of the eye movement control obtained is discussed in terms of a physiological limit and the principle of reinforcement.