The Harada-Ito procedure is an eye muscle surgery used to treat symptomatic excyclotorsion, commonly seen in cases of acquired cranial nerve 4 palsy. This condition can cause the eye to rotate outward, leading to torsional binocular diplopia. The procedure targets the anterior fibres of the superior oblique tendon, which are primarily responsible for the torsional function of the eye. By tightening or advancing these fibres toward the insertion of lateral rectus, the procedure increases incyclotorsion of the eye, helping to realign the visual axes and relieve diplopia. The Harada-Ito procedure is typically performed on patients who experience significant torsional symptoms but retain good vertical function of the superior oblique. Fell’s modification relates specifically to disinserting the isolated anterior tendon fibres and then reinserting them anteriorly and lateral to the insertion of the lateral rectus muscle. Postoperative results are generally favourable, with significant reduction of torsional diplopia.
