Tertiary Functions

1. The superior and inferior recti are adductors and assist the medial rectus, becoming more effective as adduction increases (see above for

Nasal

Temporal

Temporal

Nasal

Nasal

Temporal

Temporal

Nasal

Figure 4-3. A. The right eye from above. The superior oblique muscle acts as a depressor when the eye Is adducted. B. The superior oblique muscle acts as an inward rotator when the eye Is abducted.

comments regarding the superior rectus not being straight unless the eye is abducted). This tertiary function is nil when the eye is abducted.

2. The superior and inferior obliques assist the lateral rectus and are abductors of the already abducted eye. Their abducting function is nil when the eye is adducted.

Summary

• When the eye is abducted, the superior rectus elevates, the inferior rectus depresses, and the obliques rotate.

• When the eye is adducted, the superior oblique depresses and the inferior oblique elevates, while the superior and inferior recti rotate.

• The two elevators are the superior rectus and the inferior oblique.

• The two depressors are the inferior rectus and the superior oblique.

• The superior rectus and superior oblique are inward rotators ("SIN" may be used as a memory jogger).

• The inferior rectus and inferior oblique are outward rotators.

• The superior and inferior recti add to adduction; the two obliques add to abduction.

• The lateral and medial recti inhibit elevation and depression.

• When an extraocular muscle is paralyzed, have the patient fix with the paretic eye alone and the normal eye alone. The deviation (of the normal eye) is always greater when the paretic eye is fixating and less (of the paretic eye) when the normal eye is fixating.

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