ABSTRACT
The observation that torsion changes during vergence suggests that Listing’s law is violated. However if one examines eye position when a subject fixates targets on a near isovergence surface one finds that the eye’s position remains confined to a plane and thus Listing’s law appears to hold. Surprisingly, when one looks at actual eye positions obtained when the subject is asked to look around the room using both the eye and head, the eye positions appear to lie on a Fick-like surface rather than a volume. The model predicts that eye position generated by the vestibulo-ocular reflex should lie on a rotated Listing’s plane when the eyes are verged. This result would clearly demonstrate the existence of a static torsional command to the eye muscles. In support of the Minken model there is growing evidence for distinct tonic neurons that encode the position of each eye.
