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Extraocular muscles and the cardinal positions of gaze

  • Anatomy and physiology

Six muscles move each eye, supplied by three nerves. Testing each muscle in the gaze position where it acts alone shows which muscle or nerve is weak.

Updated

See it in 3D: Medial rectus · Lateral rectus · Superior rectus · Inferior rectus · Superior oblique · Inferior oblique · Oculomotor nerve (III) · Trochlear nerve (IV) · Abducens nerve (VI)

What it is

Each eye is moved by four rectus muscles and two oblique muscles. Most arise from a tendinous ring at the orbital apex (the annulus of Zinn); the inferior oblique arises from the orbital floor, and the superior oblique turns through a pulley (the trochlea) at the upper inner orbit. The lateral rectus is supplied by the abducens nerve, the superior oblique by the trochlear nerve, and all the others by the oculomotor nerve.

Clinical anatomy

  • Medial rectus: adducts.
  • Lateral rectus: abducts (abducens nerve, VI).
  • Superior rectus: elevates, best with the eye turned out.
  • Inferior rectus: depresses, best with the eye turned out.
  • Superior oblique: depresses the eye when it is turned in, and rotates it inwards (trochlear nerve, IV).
  • Inferior oblique: elevates the eye when it is turned in, and rotates it outwards.

Physiology

  • Yoked muscles of the two eyes receive equal commands (Hering law), so both eyes move together.
  • When a muscle contracts its direct antagonist relaxes (Sherrington law).
  • The H-shaped test puts each muscle in the position where it is the main mover.

Clinical correlation

  • Third nerve palsy: the eye rests down and out, with ptosis and sometimes a dilated pupil.
  • Fourth nerve palsy: vertical diplopia worse looking down and in; the head tilts away from the affected side.
  • Sixth nerve palsy: the eye cannot abduct; horizontal diplopia worse looking to that side.
  • Thyroid eye disease thickens the muscles, most often the inferior rectus, restricting upgaze.
  • An orbital floor fracture can trap the inferior rectus.

Next step / Initial management

  • Isolated cranial nerve palsy: follow the diplopia pathway (pupil involvement, age, vascular risk, imaging).
  • Restricted movement after trauma: CT of the orbits.
  • Restricted upgaze with lid retraction: thyroid tests and ophthalmology.
  • Childhood strabismus: paediatric ophthalmology.

Test yourself

Think of the answer, then tap the question to see it.

Which nerves supply the lateral rectus and superior oblique?

The abducens nerve (VI) supplies the lateral rectus and the trochlear nerve (IV) the superior oblique.

In which gaze position is the superior oblique tested?

Looking down with the eye turned in (adducted).

Which muscle is most often enlarged in thyroid eye disease?

The inferior rectus, which restricts upgaze.

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See it in 3D9

The structures of Durgical's 3D anatomy where it is found.

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Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once.

Sources: Anatomy, Head and Neck, Eye Extraocular Muscles (StatPearls Publishing (NCBI Bookshelf), 2022); Anatomy, Head and Neck: Eye Superior Oblique Muscle (StatPearls Publishing (NCBI Bookshelf), 2023); Anatomy, Head and Neck: Eye Lateral Rectus Muscle (StatPearls Publishing (NCBI Bookshelf), 2023).

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