[Optico-geometric axes of the eye: application to the alpha angle and its representatives. Review of the literature].

The different positions of the corneal reflex and the center of the pupil demonstrates the decentration of the ocular structures. The optic axis and the visual axis are different. They form a angle (defined as angle alpha) important for appreciation of strabismic deviation. This phenomenon is well-known since the nineteen century. This review discusses the different definitions of the optico-visual axes and angles (angle alpha, gamma, kappa, lambda). A possible clinical application is discussed.