Rotation of listing's plane with convergence: Independence from eye position

PURPOSE. To determine whether asymmetrical vergence results in a rotation o f Listing's plane independent of vergence-associated changes of eye positio n in the orbit. METHODS. Six normal subjects were required to fixate on a 3 X 3 array (40 d egrees on a side) of light-emitting diodes arranged on a flat screen 124 cm from the subject. Disparity-induced vergence was elicited with a horizonta l Fresnel prism (30 cm/m, similar to 17 degrees) placed in front of one eye . In four subjects accommodative vergence (10 degrees to 15 degrees) was pr oduced by placing a minus spherical lens in front of one eye while the othe r eye was covered. Eye position was measured binocularly using three-axis s earch coils. Control data were collected without prisms during monocular an d binocular viewing. For all data a planar regression was used to fir. tors ional eye position as a function of horizontal and vertical position to cal culate the horizontal and vertical primary positions that define the orient ation of Listing's plane. RESULTS. In the prism experiment, the horizontal primary position of the ey e not wearing the prism rotated temporally by 3.9 degrees +/- 1.7 degrees c ompared with the both eyes viewing control condition. The rotation of the p rism eye was in a similar range (3.4 degrees +/- 2.0 degrees). With accommo dation, the horizontal primary position of the viewing eye rotated temporal ly by 4.4 degrees +/- 1.4 degrees compared with the monocular viewing contr ol. In both the accommodation and the prism paradigms there was usually a r otation of vertical primary position downward. CONCLUSIONS. Vergence-induced changes in Listing's plane can be independent of changes in orbital position associated with vergence. This finding supp orts a role for changes in central innervation in the elaboration of Listin g's law.