Annulus of Zinn

Orbit – Anterior view – showing Annulus of zinn, intraocular muscles and nerves
Click on Image for an enlarged view
Image by Patrick J. Lynch
  • Annulus of zinn is a fibrous ring located in the posterior part of the orbit
  • It is located around the optic canal and encloses a part of the superior orbital fissure
  • It is the common fibrous origin of the 4 recti muscles
  • It is named after Johann Gottfried Zinn


  • According to some workers, the annulus of zinn has 2 parts:
    • upper part – superior tendon of Lockwood – gives origin to superior rectus, part of medial rectus, and upper head of lateral rectus
    • lower part – ligament / tendon of Zinn – gives origin to inferior rectus, part of medial rectus and lower head of lateral rectus

Structures passing through the ring:

  • Through optic canal
    • Optic nerve
    • Ophthalmic artery
  • Through superior orbital fissure
    • Superior and inferior divisions of oculomotor nerve
    • Abducens nerve
    • Nasociliary branch of ophthalmic nerve

Structures attached to the ring:

  • The 4 recti muscles
  • The origins of levator palpebrae superioris and superior oblique are partly attached to the ring even though they lie outside it

Alternate names :

  • Annular tendon
  • Common tendinous ring
  • annulus tendineus communis

Other structures with similar names:

  • Zonule of Zinn
  • Circle of Zinn

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