1. Medial Rectus Function
2. Medial Rectus Eye

The inferior oblique muscle or obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit. The inferior oblique is an extraocular muscle, and is attached to the maxillary bone (origin) and the posterior, inferior, lateral surface of the eye (insertion). The inferior oblique is innervated by the inferior branch of the oculomotor nerve.

Structure[edit]

Inferior rectus muscle. The inferior rectus eye muscle is located at the bottom part of the eye and allows the eye to move downward. This muscle’s movement is controlled by the oculomotor nerve. Oblique muscles. There are two oblique muscles of the eye. These muscles are: Superior oblique muscle. Inferior oblique muscle. The incision is made by cutting straight down through the conjunctiva in the white zone between the inferior rectus ( IR) and medial rectus ( MR) muscles, approximately 8 mm posterior to the limbus. Extend the conjunctival incision from the inferior rectus muscle to within 1–2 mm of plica. ( b) The location and alignment of the initial incision. Typical space from limbus is: Medial rectus, 5 millimeters Inferior rectus, 6 millimeters Lateral rectus, 7 millimeters Superior rectus, 8 millimeter. Oblique Muscles. The oblique muscles of the orbit are superior and inferior. Their origin and insertion are as follows: Superior Oblique. Origin: from body of sphenoid superomedial to the optic. Is weakness of both the superior rectus and inferior oblique. A worsening in upgaze also occurs in inferior oblique overaction, since the affected eye will elevate more than normal in upgaze. A worsening of horizontal diplopia in lateral gaze in one direction implicates either the ipsilateral lateral rectus or contralateral medial rectus.

The inferior oblique arises from the orbital surface of the maxilla, lateral to the lacrimal groove. Unlike the other extraocular muscles (recti and superior oblique), the inferior oblique muscle does not originate from the common tendinous ring (annulus of Zinn).

Passing lateralward, backward, and upward, between the inferior rectus and the floor of the orbit, and just underneath the lateral rectus muscle, the inferior oblique inserts onto the scleral surface between the inferior rectus and lateral rectus.

In humans, the muscle is about 35 mm long.^[1]

Innervation[edit]

The inferior oblique is innervated by the inferior division of the oculomotor nerve (cranial nerve III).

Function[edit]

Its actions are extorsion, elevation and abduction of the eye.

Primary action is extorsion (external rotation); secondary action is elevation; tertiary action is abduction (i.e. it extorts the eye and moves it upward and outwards). The field of maximal inferior oblique elevation is in the adducted position.

The inferior oblique muscle is the only muscle that is capable of elevating the eye when it is in a fully adducted position.^[2]

Medial Rectus Function

Clinical significance[edit]

While commonly affected by palsies of the inferior division of the oculomotor nerve, isolated palsies of the inferior oblique (without affecting other functions of the oculomotor nerve) are quite rare.

'Overaction' of the inferior oblique muscle is a commonly observed component of childhood strabismus, particularly infantile esotropia and exotropia. Because true hyperinnervation is not usually present, this phenomenon is better termed 'elevation in adduction'.^[3]

Surgical procedures of the inferior oblique include: loosening (also known as recession see Strabismus surgery), myectomy, marginal myotomy, and denervation and extirpation. It is also encountered and identified in lower lid blepharoplasty surgeries.

Additional images[edit]

• Eye movement of lateral rectus muscle, superior view

• Eye movement of medial rectus muscle, superior view

• Eye movement of inferior rectus muscle, superior view

• Eye movement of superior rectus muscle, superior view

• Eye movement of superior oblique muscle, superior view

• Eye movement of inferior oblique muscle, superior view

• Anterior view

• Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.

• Inferior oblique muscle

• Extrinsic eye muscle. Nerves of orbita. Deep dissection.

• Extrinsic eye muscle. Nerves of orbita. Deep dissection.

References[edit]

This article incorporates text in the public domain from page 1023 of the 20th edition ofGray's Anatomy(1918)

1. ^Riordan-Eva, P (2011). Vaughan & Asbury's General Ophthalmology (18th ed.). New York: McGraw-Hill Medical. ISBN978-0071634205.
2. ^'Eye Theory'. Cim.ucdavis.edu. Archived from the original on 2014-05-27. Retrieved 2012-12-07.
3. ^Kushner BJ (2006). 'Multiple mechanisms of extraocular muscle 'overaction''. Arch Ophthalmol. 124 (5): 680–8. doi:10.1001/archopht.124.5.680. PMID16682590.

External links[edit]

Medial Rectus Eye

• Anatomy figure: 29:01-08 at Human Anatomy Online, SUNY Downstate Medical Center
• lesson3 at The Anatomy Lesson by Wesley Norman (Georgetown University) (orbit5)