The Obliquus oculi inferior (inferior oblique) is a thin, narrow muscle placed near the anterior margin of the floor of the orbit

Orbit (anatomy)

In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...

.

Action

Its actions

Muscles of orbit

The muscles of the orbit are a group of six muscles that control movement of the eye. Four of the muscles control the movement of the eye in the four cardinal directions: up, down, left and right...

 are lateral rotation, elevation and abduction of the eye.

Primary action is extorsion; secondary action is elevation

Elevation (kinesiology)

Elevation, in kinesiology is the anatomical term of motion for movement in a superior direction.It is the opposite of depression.-Muscles:* elevation of the scapula at the shoulders Elevation, in kinesiology is the anatomical term of motion for movement in a superior direction.It is the opposite of...

; tertiary action is abduction

Abduction (kinesiology)

Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:* of arm at shoulder ** Supraspinatus** Deltoid* of hand at wrist...

 (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.

Path

The inferior oblique arises from the orbital surface of the maxilla

Maxilla

The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

, lateral to the lacrimal groove

Lacrimal groove

On the nasal surface of the body of the maxilla, in front of the opening of the sinus is a deep groove, the lacrimal groove , which is converted into the nasolacrimal canal, by the lacrimal bone and inferior nasal concha; this canal opens into the inferior meatus of the nose and transmits the...

.

Passing lateralward, backward, and upward, between the inferior rectus and the floor of the orbit, the inferior oblique inserts onto the sclera

Sclera

The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest...

l surface between the inferior rectus and lateral rectus.

The origin of the inferior oblique muscle is not on the common tendinous ring (annulus of Zinn

Annulus of Zinn

The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the origin for five of the six extraocular muscles...

).

Innervation

The inferior oblique is innervated by the inferior division of the oculomotor nerve

Oculomotor nerve

The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...

 (cranial nerve III).

Clinical significance

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

Strabismus

Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...

, particularly infantile esotropia

Esotropia

Esotropia is a form of strabismus, or "squint", in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance...

 and exotropia

Exotropia

Exotropia is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia. People with exotropia often experience crossed diplopia. Intermittent exotropia is a fairly common condition. "Sensory exotropia" occurs in the presence of poor vision...

. Because true hyperinnervation is not usually present, this phenomenon is better termed "elevation in adduction".

Surgical procedures of the inferior oblique include: loosening (also known as recession see Strabismus surgery

Strabismus surgery

Strabismus surgery is surgery on the extraocular muscles to correct the misalignment of the eyes. With approximately 1.2 million procedures each year, extraocular muscle surgery is the third most common eye surgery in the United States.-Types:...

), myectomy, marginal myotomy, and denervation and extirpation.

External links

• Image at childrenshospital.org