The inferior oblique is one of the six extra-ocular muscles, the only one not arising from the orbital apex. It pulls the front of the eye upward and outward, making it the primary elevator of the adducted eye. Overaction of the inferior oblique produces the V-pattern strabismus with increasing divergence in upgaze. It is the muscle injected with botulinum toxin for vertical strabismus management and is weakened surgically (inferior oblique recession or myectomy) for overaction.
| Origin | Floor of the orbit near the nasolacrimal canal |
|---|---|
| Insertion | Lateral sclera of the eyeball posterior to the equator |
| Nerve Supply | Inferior division of the oculomotor nerve (CN III) |
| Blood Supply | Infraorbital artery |
| Actions | Elevation of the eye (primary when adducted); Abduction of the eye; External rotation (extorsion) of the eye |
|---|
In the adducted position (eye looking toward the nose) the inferior oblique is the primary elevator, while the superior rectus is the primary elevator in the abducted position. This position-dependent action is why isolated inferior oblique palsy produces hypotropia (eye turning down) that is most visible in contralateral gaze.
Inferior oblique overaction produces the V-pattern esotropia where the eyes diverge in upgaze (both inferior obliques pulling the eyes outward when they look up). Inferior oblique weakening procedures (recession or myectomy) are performed during strabismus correction. The inferior oblique muscle belly is approached through the inferior oblique pocket between the inferior rectus and lateral rectus muscles during strabismus surgery.
Not accessible to external palpation. Assessed by cover-uncover test and alternate cover test measuring the deviation in different gaze positions.
Excessive inferior oblique strength producing V-pattern strabismus with divergence in upgaze managed with inferior oblique weakening surgery.
