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The primary (main) action of the superior oblique muscle is intorsion (internal rotation), [1] the secondary action is depression (primarily in the adducted position) and the tertiary action is abduction (lateral rotation). The extraocular muscles rotate the eyeball around vertical, horizontal and antero-posterior axes.
To summarize, the actions of the superior oblique muscle are (1) depression of the eyeball, especially when the eye is adducted; and (2) intorsion of the eyeball, especially when the eye is abducted. The clinical consequences of weakness in the superior oblique (caused, for example, by fourth nerve palsies) are discussed below.
Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye. The other muscle, the levator palpebrae superioris, controls eyelid elevation. The actions of the six muscles responsible for eye movement depend on the position of the eye at the time of muscle contraction. [2]
The trochlear nerve is tested by examining the action of its muscle, the superior oblique. When acting on its own this muscle depresses and abducts the eyeball. However, movements of the eye by the extraocular muscles are synergistic (working together). Therefore, the trochlear nerve is tested by asking the patient to look 'down and in' as the ...
In the primary position (eyes straight ahead), both of these groups contribute to vertical movement. Elevation is due to the action of the superior rectus and inferior oblique muscles, while depression is due to the action of the inferior rectus and superior oblique muscles. When the eye is abducted, the recti muscles are the prime vertical movers.
The physiologic basis of the head tilt test was explained by Alfred Bielschowsky and Hofmann [8] in 1935. [9] However, Nagel described it 30 years prior to Bielschowsky when he noted that the combined action of the superior rectus muscle and the superior oblique muscle of one eye and of the inferior rectus and inferior oblique muscles in the fellow eye causes incycloduction and excycloduction ...
The trochlear nerve controls the superior oblique muscle to rotate the eye along its axis in the orbit medially, which is called intorsion, and is a component of focusing the eyes on an object close to the face. The oculomotor nerve controls all the other extraocular muscles, as well as a muscle of the upper eyelid. [3]
The fourth cranial nerve innervates the superior oblique muscle for each eye. The superior oblique muscle is one of the six extraocular muscles that allow movement of eye. Specifically, the superior oblique muscle primarily intorts the eye (such that the top of the eye rolls toward the nose), with secondary actions of depression (downgaze) and ...