Inferior Rectus

General information

Inferior rectus muscle is part of the extraocular muscles along with five other muscles. Four of these muscles, including the inferior rectus, control eye movement in the cardinal directions.

Literal meaning

The inferior straight muscle (of the eye).

Interesting information

Although the main function of this muscle is eyeball depression, it also acts to control eyeball movement and the direction of gaze in coordination with the other extraocular muscles.

Origin

Common tendinous ring (Annulus of Zinn).

Insertion

Anterior half of eyeball (posterior to corneoscleral junction).

Function

Depresses, adducts, externally rotates eyeball.

Nerve supply

Oculomotor nerve (CN III).

Blood supply

Ophthalmic artery, infraorbital artery.

Relevant research

The inferior rectus muscle can become inflamed in patients with thyroid eye disease causing fibrotic changes in the muscles leading to hypotropia and reduced eye elevation. For these reasons, Bell’s phenomenon may be decreased in these patients and only improve after inferior rectus recession. Bell’s phenomenon, a reflex observed when the eye moves upward and outward during attempted eyelid closure or during incomplete blinking and occurs behind forcibly closed eyelids in normal individuals.

Takahashi, Y., Sabundayo, M. S., Mito, H., Miyazaki, H., & Kakizaki, H. (2017). Bell's phenomenon in thyroid-associated inferior rectus myopathy. Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie, 255(12), 2467–2471.

Inferior rectus exercises

None