Showing papers by "Clifton M. Schor published in 2007"

Variation of binocular-vertical fusion amplitude with convergence

Abstract: Purpose The maximum binocular vertical disparity that can be fused with disparity vergence (vertical-fusion amplitude or VFA), varies with convergence angle VFA is larger for convergence responses to near than to far viewing distances; however the clinical norms for changes in VFA with convergence have not been established VFA at several convergence angles was measured to obtain a quantitative description of the changes in VFA with convergence

A virtual ophthalmotrope illustrating oculomotor coordinate systems and retinal projection geometry.

Abstract: Eye movements are kinematically complex. Even when only the rotational component is considered, the noncommutativityof 3D rotations makes it hard to develop good intuitive understanding of the geometric properties of eye movements andtheir in!uence on monocular and binocular vision. The use of at least three major mathematical systems for describing eyepositions adds to these dif"culties. Traditionally, ophthalmotropes have been used to visualize oculomotor kinematics. Here,we present a virtual ophthalmotrope that is designed to illustrate Helmholtz, Fick, and rotation vector coordinates, as well asListing’s extended law (L2), which is generalized to account for torsion with free changing vergence. The virtualophthalmotrope shows the in!uence of these oculomotor patterns on retinal projection geometry.Keywords: eye movements, binocular vision, geometry, coordinate systems, rotation vectors, Listing’s law, Donder’s law, L2Citation: Schreiber, K. M., & Schor, C. M. (2007). A virtual ophthalmotrope illustrating oculomotor coordinate systems andretinal projection geometry. Journal of Vision, 7(10):4, 1–14, http://journalofvision.org/7/10/4/, doi:10.1167/7.10.4.

Illusory contrast-induced shifts in binocular visual direction bias saccadic eye movements toward the perceived target position.

Abstract: The perceived binocular visual direction of a fused disparity stimulus with an interocular contrast difference is biased toward the direction signaled by the eye presented with the higher contrast image (J. S. Mansfield & G. E. Legge, 1996). Does the amplitude of binocular saccadic eye movements have a similar bias? We examined saccades to fused disparate Gabor patches with interocular contrast differences. The effect of these contrast differences on saccadic amplitudes was compared to the perceptual biases in binocular direction obtained in a vernier acuity task. Saccades to unequal contrast targets landed between the end points for equal contrast and monocular targets. For three of our eight subjects, the saccadic bias equaled the perceptual effect. For the other subjects, however, saccades were affected to a lesser extent. Three models for binocular combination were used to evaluate these responses: A maximum-likelihood model failed to predict our results, whereas a model with contrast-dependent weighting of direction estimates by two monocular channels and a gain control model of binocular contrast summation gave a better approximation to our data. Both models showed that for the perceptual system, the influence of the eye that was presented with the higher contrast image was more dominant in the binocular combination than expected from the stimulus contrast ratio. The oculomotor system, however, was close to following linear summation.