Which muscle has excyclotorsion as its secondary action?

• A. Lateral Rectus
• B. Superior Rectus
• C. Superior Oblique
• D. Inferior Rectus

Answer: (D)

Excyclotorsion is outward rotation of the top of the eye. Among the extraocular muscles, torsional effects appear as secondary actions to the primary vertical or horizontal moves. The inferior rectus, when it depresses the eye, also contributes to extorsion (excyclotorsion) as a secondary action. That combination—depressing the eye with outward rotation of the top—fits the scenario exactly, making it the muscle whose secondary action is excyclotorsion.

The other muscles either intort (the superior rectus and the superior oblique) or extort as a primary action (the inferior oblique), so their torsional effect isn’t excyclotorsion as a secondary action. Lateral rectus mainly governs horizontal movement with little consistent torsional contribution.