torsion
Torsion is a rotation of the eye around its anteroposterior axis, the Y (sagittal) axis that runs through the globe from front to back.1 The superior limbus turns nasally in intorsion and temporally in extorsion.1 The anteroposterior axis coincides with the line of sight, so torsion is a wheel rotation of the eye around its own line of sight.1,2
Torsional movements keep images upright when the head tilts, and in these righting reflexes the superior limbi of both eyes rotate away from the side of the tilt.1 On head tilt to the right, the right eye intorts and the left eye extorts.1 Cyclorotations of this kind occur with postural changes of the head and body, and binocular vision also requires cyclovergences to correct misaligned vertical meridians of the two eyes.2
More detail
Rotation around the line of sight is severely restricted, because unrestricted cyclorotations would cause great difficulty with spatial orientation.2 Donders stated in 1848 that each position of the line of sight carries one definite orientation of the horizontal and vertical retinal meridians, whatever path the eye took to reach that position.2
Sources (8)
- Kanski, Clinical Ophthalmology (2024), ch. 18
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 4
- American Academy of Ophthalmology. 2020. Pediatric Ophthalmology/Strabismus: Basic and Clinical Science Course. San Francisco: American Academy of Ophthalmology.
- Ansons, A.M. and Davis, H. eds. 2014. Diagnosis and management of ocular motility disorders. 4th ed. Oxford: Wiley-Blackwell.
- Noorden, G.K. and Campos, E.C. 2002. Binocular vision and ocular motility: theory and management of strabismus. 6th ed. St. Louis: Mosby.
- Rutstein, R. and Daum, K. 1997. Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
- Rowe, F.J. 2012. Clinical orthoptics. 3rd ed. Oxford: Wiley-Blackwell.
- Von Noorden, G.K. and Campos, E.C. 2002. Binocular vision and ocular motility: theory and management of strabismus. 6th ed. St. Louis: Mosby.
Reviewed October 2026