Geometric Study of Human Binocular Vision with Misaligned Eye Optics

Abstract The healthy human eye’s optical components are misaligned, which has been overlooked in studies of binocular vision. This study presents comprehensive ge-ometric constructions in the binocular system, with the eye model incorporating the fovea that is not located on and the lens that is tilted away from the eye’s optical axis. It includes the vertical misalignment of optical components and the 3D binocular field of fixations with the previously considered horizontal misalign-ment underlying stereopsis. The consequences and functional roles of vertical misalignment are explained in the following finding: The classic Helmholtz the-ory, which states that the subjective vertical retinal meridian inclination to the retinal horizontal meridian explains the perceived backward tilt of the vertical horopter, is less relevant when the eye’s optical components are misaligned. In-stead, the lens vertical tilt provides the retinal vertical criterion. The typical misalignment of the fovea and lens in the human population confirms the exper-imentally measured vertical horopter’s inclination.