What is the tertiary action of the superior rectus?

• A. Adduction
• B. Elevation
• C. Abduction
• D. Excyclotorsion

Answer: (A)

The idea to focus on is that an extraocular muscle doesn’t just do one movement; it has primary, secondary, and tertiary actions based on how its pull translates to motion of the eye. For the superior rectus, the primary action is lifting the eye (elevation). The secondary action is adduction (movement toward the nose). The tertiary action is intorsion (incyclotorsion), which rotates the top of the eye toward the nose.

Intorsion helps maintain stable torsion when the eye moves in elevation or adduction. Among the options given, adduction matches the muscle’s secondary action, not its tertiary. The torsional action would be intorsion, which isn’t listed here (the opposite torsion would be excyclotorsion). The other options describe primary elevation or horizontal movements or the opposite torsion. So the key takeaway is that the tertiary action is intorsion, which isn’t represented by the listed choices.