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Orbicularis oculi muscle (Preseptal part)

The orbicularis oculi muscle is a thin, flat, circular muscle found in the eyelid and around the orbital rim, essential for eyelid closure and eye protection. The preseptal part is a specific subdivision of the palpebral portion, lying superficially over the orbital septum but deep to the skin and subcutaneous tissue. It plays a vital role in gentle eyelid closure and the distribution of tears across the ocular surface.

Synonyms

  • Preseptal portion of orbicularis oculi

  • Preseptal orbicularis

  • Palpebral orbicularis oculi (preseptal)

Function

  • Responsible for gentle closure of the eyelids (blinking, sleeping)

  • Assists in spreading the tear film across the cornea

  • Aids in drainage of tears via the lacrimal pump mechanism

Origin

  • Originates from the medial palpebral ligament and adjacent bone of the medial orbital margin

Insertion

  • Inserts into the lateral palpebral raphe and merges with adjacent muscle fibers at the lateral canthus

Nerve Supply

  • Supplied by the temporal and zygomatic branches of the facial nerve (cranial nerve VII)

Arterial Supply

  • Branches from the ophthalmic artery (particularly the palpebral branches)

  • Additional contribution from branches of the facial artery

Venous Drainage

  • Drained by the palpebral veins into the superior and inferior ophthalmic veins

MRI Appearance

  • T1-weighted images: Intermediate to low signal intensity, distinguishing it from adjacent orbital fat (high signal).

  • T2-weighted images: Normal muscle demonstrates relatively low signal intensity, but increased signal may indicate edema or pathology.

  • STIR (Short Tau Inversion Recovery): Muscle shows low signal intensity in healthy tissue; hyperintensity is seen if there is edema, inflammation, or acute injury.

CT Appearance

  • Appears as a thin, soft tissue density band anterior to the orbital septum, outlining the eyelid structure

  • Distinguishable from adjacent orbital fat and septum by its linear configuration and location

MRI images

Orbicularis oculi muscle (Preseptal part) mri axial image 1 -img-00000-00000