SURVEY OF OPHTHALMOLOGY VOLUME 49 • NUMBER 6 • NOVEMBER–DECEMBER 2004 MAJOR REVIEW Listing’s Law: Clinical Significance and Implications for Neural Control Agnes M.F. Wong, MD, PhD, FRCSC Department of Ophthalmology and Vision Sciences, and Division of Neurology, University of Toronto, University Health Network and The Hospital for Sick Children, Toronto, Ontario, Canada Abstract. Listing’s law governs the three-dimensional orientation of the eye and its axes of rotation. It states that, when the head is fixed, there is an eye position called primary position, such that the eye assumes only those orientations that can be reached from primary position by a single rotation about an axis in a plane called Listing’s plane. Listing’s law can also be expressed in terms of any initial eye position, not just primary position (Listing’s half-angle rule). The binocular extension of Listing’s law is equivalent to Listing’s law when the vergence angle is zero, and adjusts the eyes’ torsion when they converge. Listing’s law holds during fixation, saccades, smooth pursuit, and vergence, but not during sleep and vestibulo-ocular reflex, suggesting that it is actively implemented by a neural mechanism. Orbital constraints, such as “pulleys,” may also play a role. Adherence to Listing’s law and its extension may serve the purpose of optimizing motor efficiency, or simplifying neural processing for binocular vision, or both. The study of Listing’s law not only allows us to understand the organization of neural and mechanical factors in the control of three-dimensional eye movements, it also has important clinical implications for strabismus and the optimal management of this disorder. (Surv Ophthalmol 49:563–575, 2004.  2004 Elsevier Inc. All rights reserved.) Key words. Listing’s law • torsion • three dimension • eye movements • kinematics • saccades • smooth pursuit • vestibulo-ocular reflex • vergence • pulleys I. Introduction How the eye rotates during eye movement has been a fascinating subject for centuries. From 1846 to 1868, Ruete, Donders, Listings, Fick, Helmholtz and many others published seminal works on this topic that still exert influence today. The great 19th-century physi- ologist Hermann von Helmholtz 73 devoted over 50 pages in his book Treatise on Physiological Optics to what he called Listing’s law, a principle that governs three-dimensional (horizontal, vertical, and tor- sional) eye movements. However, despite the atten- tion that Helmholtz gave to Listing’s law, 20 th century 563  2004 by Elsevier Inc. 0039-6257/04/$–see front matter All rights reserved. doi:10.1016/j.survophthal.2004.08.002 physiologists have mostly ignored it, largely because understanding three-dimensional eye movements requires a strong knowledge of kinematics (the study of motion) and of the mathematical language used to describe rotary motions. The lack of understanding of subtle kinematic concepts and mathematical language has perpetuated a general sense of confusion about Listing’s law among ophthalmologists. The last 10 years have brought a resurgence of interest in Listing’s law. Although confusion abounds because of the advanced mathematical language used in the literature, a fundamental understanding of