Inferior oblique muscle
The Obliquus oculi inferior (inferior oblique) is a thin, narrow muscle, placed near the anterior margin of the floor of the orbit.
Its actions are lateral rotation, elevation and abduction of the eye.
Primary action is extorsion; secondary action is elevation; tertiary action is abduction (i.e. it extorts the eye and moves it upward and outward). The field of maximal inferior oblique elevation is in the adducted position.
Passing lateralward, backward, and upward, between the inferior rectus and the floor of the orbit, the inferior oblique inserts onto the scleral surface between the inferior rectus and lateral rectus.
It is the only muscle of eye movement whose origin is not on the common tendonous ring (annulus of Zinn).
The inferior oblique is innervated by the inferior division of the oculomotor nerve (cranial nerve III).
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".
- Kushner BJ (2006). "Multiple mechanisms of extraocular muscle 'overaction'". Arch Ophthalmol. 124 (5): 680–8. PMID 16682590.
Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
- Template:NormanAnatomy (Template:NormanAnatomyFig)
- Image at childrenshospital.org