Investigating the Overaction of the Inferior Oblique Muscle and Associated Vertical Strabismus: Indications, Timing, and Methods of Surgical Intervention

Treatment of the vertical strabismus due to the overaction of the inferior oblique extraocular muscle usually requires surgical intervention. In addition to the cosmetic issues, the main indications for surgical treatment of the inferior oblique overaction are the presence of cyclotropia and torsional diplopia. Most procedures target the weakening of the inferior oblique muscle; however, there is the risk of some intraoperative and postoperative complications, including highly invasive procedures, difficulty of technical implementation because of the need for manipulations in inaccessible locations of the globe near the optic nerve, macular area, and large vessels, long duration of the surgery, inability to determine the dosage of the outcomes of the surgery, and poor functional outcomes. Most complications are absent in the procedure of anterior transposition in which the neuro-fibrovascular bundle serves as the axis of rotation of the inferior oblique muscle. This technique changes the inferior oblique muscle’s action field and increases treatment effectiveness. Despite the advantages of this technique, its application is still limited because of the lack of methods for controlling the amount of anterior transposition to treat inferior oblique overaction, particularly of small degrees.