Abstract
The eye model that continues to influence theoretical developments in binocular vision assumes that the optical node coincides with the center of rotation for eye movements. This anatomically incorrect assumption was originally made about two centuries ago in the construction of the Vieth-Müller circle (V-MC). In this presentation, we construct the precise geometry for binocular projections when the nodal point is placed at the anatomically correct location. We prove that, in this case, there is an infinite family of 3D geometric horopters with two perpendicular components. The first component consists of the horizontal horopters parametrized by vergence and the point of the V-MC. For a constant value of vergence, the horizontal horopters intersect at the point of symmetric convergence on the corresponding V-MC. The second component is formed by straight lines parametrized by vergence. Each of these straight lines is perpendicular to the visual plane and passes through the point of symmetric convergence. The main result is the relative disparity's dependence on the eye's position. We evaluate the difference between the geometric horopter and the V-MC for near-habitual fixation distances. Finally, we discuss the impact this difference may have for depth discrimination and other visual functions that make use of disparity processing.