Excyclotorsion is a term applied to the outward, torsional (rotational) movement of the eye, mediated by the inferior oblique muscle of the eye. The inferior oblique muscle is innervated by cranial nerve III (oculomotor nerve).
Excyclotorsion may also be used to describe the condition or state of the eye when a patient has a cranial nerve IV (trochlear nerve) palsy. The trochlear nerve supplies the superior oblique muscle, and when this muscle is non-functional (as in trochlear palsy) the eye excyclotorts; i.e. twists/rotates outward.
This excyclotorsion may be corrected through surgery using the Harada-Ito procedure.