The dominant eye has often been denned as the eye whose input is favored in behavioral coordinations in which only one eye can be used, the eye preferred when monocular views are discrepant, or the eye manifesting physiological or refractive superiority. Although its functional significance has not yet been ascertained, patterns of ocular dominance have been shown to be related to a large number of perceptual, performance, and clinical phenomena. The nature of these relationships has remained obscure due to the variety of alternative tests for and theoretical definitions of eye dominance.