The Obliques

These are also vertical yoke muscles but they run on a different line to the vertical recti. The superior oblique depresses the adducted eye (makes

Intorts the adducted eye Elevates the abducted eye

Figure 14.4. Primary and secondary actions of the superior rectus muscle.O

Intorts the adducted eye Elevates the abducted eye

Figure 14.4. Primary and secondary actions of the superior rectus muscle.O

the eye go down when it is turned in) and the inferior oblique elevates the adducted eye.

When a patient has a fourth cranial nerve palsy on the right side, the right eye can no longer look down when it is turned in because of the defective action of the superior oblique muscle. Double vision is experienced, which is maximal (i.e., widest displacement of images) when looking down to the left.

When a patient has a sixth cranial nerve palsy on the right side, the right eye can no longer abduct or turn outwards. A right convergent squint is seen and the patient experiences double vision, which is worse when looking to the right. There might be a head turn to the right.

When a patient has a third cranial nerve palsy on the right side, the right eye is turned down and to the right and, if the palsy is complete, the upper lid droops and the pupil is dilated. Movement of the eye is limited.

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