Topics

Topic

design image
Orbicularis oculi muscle

The Orbicularis oculi is a circular, sphincter-type muscle of facial expression located around the eye. It plays a crucial role in eyelid closure and protection of the ocular surface. This muscle is composed of several distinct parts, including the orbital, palpebral, and lacrimal segments, which allow for nuanced movements of the eyelids, from gentle blinking to forceful closure. The orbicularis oculi is innervated by the facial nerve (cranial nerve VII), making it essential for voluntary and involuntary blinking and other eye-protective reflexes.

Synonyms

  • Musculus orbicularis oculi

  • Orbicular eye muscle

  • Eyelid sphincter muscle

Function

  • Responsible for closing the eyelids (blinking, winking, and forceful closure)

  • Assists in the drainage of tears by compressing the lacrimal sac

  • Protects the cornea and eyeball from injury and foreign particles

  • Plays a role in facial expression, particularly squinting and frowning

MRI Appearance

  • T1-Weighted Images:

    • The Orbicularis oculi muscle appears as an intermediate to low signal intensity structure, similar to other skeletal muscles.

  • T2-Weighted Images:

    • Exhibits intermediate to slightly low signal intensity.

  • STIR (Short Tau Inversion Recovery):

    • The muscle appears as low to intermediate signal, with increased signal intensity seen in cases of edema, inflammation, or muscle injury.

CT Appearance

  • Appears as a thin, well-defined, soft tissue density band encircling the orbital rim and eyelids

  • Shows homogenous soft tissue attenuation, slightly denser than orbital fat

  • May become thickened or more prominent in cases of trauma, inflammation, or neoplastic involvement

MRI images

Orbicularis oculi muscle mri sagittal t2 image

CT image

Orbicularis oculi muscle CT axial image-img-00000-00000

CT image

Orbicularis oculi muscle CT axial image-img-00000-00000_00001