While there are several coordinate systems that are useful for mathematical modeling of rotations of the eye, ocular rotations are clinically considered as horizontal rotations about a vertical axis, corresponding to medial and lateral gaze; vertical rotations about a horizontal axis, corresponding to upward and downward gaze; and torsional rotations about the line of sight. If a change in gaze position is broken down into a series of separate rotations about the horizontal and vertical axes, the final torsion of the eye for a given gaze direction could theoretically vary, depending on the sequence in which the rotations are applied. In practice, the final torsion of the eye is always the same for a given gaze direction, regardless of the sequence by which it arrives there (Donder’s law). Listing’s law specifies this relationship by stipulating that the orientation in a given gaze position is equivalent to that which would result from a single rotation around an axis lying in Listing’s plane.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.