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yoke muscles

Yoke muscles are pairs of extraocular muscles, one in each eye, that move the two eyes in the same direction. The right medial rectus and the left lateral rectus, for example, are yoke muscles that turn both eyes to the left.1 The elevators of one eye, the superior rectus and inferior oblique, are yoked as a unit to the elevators of the fellow eye, and the depressors are yoked the same way.1

Hering's law of equal innervation governs yoke muscles, so an agonist in one eye and its yoke muscle in the fellow eye receive equal nerve impulses.2,3 The fixing eye sets the innervation. A paretic eye that fixates therefore produces a larger secondary deviation than the primary deviation seen when the normal eye fixates.2

Yoking changes with the type of eye movement. The medial rectus of one eye is yoked with the lateral rectus of the other eye in lateroversion, and the two medial recti are yoked during convergence.1 Some texts extend the term to pairs that rotate the eyes in opposite directions.3

More detail

The six yoke pairs for version movements are left medial rectus with right lateral rectus, left lateral rectus with right medial rectus, left superior rectus with right inferior oblique, left inferior rectus with right superior oblique, left superior oblique with right inferior rectus, and left inferior oblique with right superior rectus.2 Hering's law calls each muscle's yoke its contralateral synergist, so the right superior oblique is the contralateral synergist of the left inferior rectus.3

Sources (20)
  1. von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 4
  2. Yanoff and Duker, Ophthalmology (2023), ch. 11
  3. Pickwell's Binocular Vision Anomalies, ch. 17
  4. Leigh, R. and Zee, D. (2015). The Neurology of Eye Movements. 5th ed. New York: Oxford University Press.
  5. Purves, D., Augustine, G., Fitzpatrick, D., Hall, W., LaMantia, A., McNamara, J. and White, L. (2014). Neuroscience. 5th ed. Sunderland: Sinauer Associates.
  6. Rutstein, R. and Daum, K. (1997). Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
  7. Scheiman, M. and Wick, B. (2014). Clinical Management of Binocular Vision. 4th ed. Philadelphia: Lippincott Williams & Wilkins.
  8. von Noorden, G. and Campos, E. (2002). Binocular Vision and Ocular Motility. 6th ed. St. Louis: Mosby.
  9. PubMed Central: NBK217 secondary
  10. JAMA Network: 267803
  11. PubMed Central: PMC2704533
  12. PubMed Central: NBK10793 secondary
  13. PubMed Central: NBK406 secondary
  14. EyeWiki: Extraocular_Muscles
  15. American Academy of Ophthalmology: cardinal-positions-yoke-muscles-3
  16. American Academy of Ophthalmology: bcscsnippetdetail.aspx?id=0aafb0a4-d35d-40c5-b823-a9d6e312a3
  17. Medscape: 1189759-overview secondary
  18. oxfordreference.com: acref-9780191830099-e-599
  19. Springer: 978-981-287-846-5_17
  20. dictionary.com: yoked

Reviewed October 2026

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