The Effect of Anterior Transposition of the Inferior Oblique Muscle on the Palpebral Fissure

Abstract

Background: Anterior transposition of the inferior oblique muscle is a popular treatment for dissociated vertical divergence. It seems that this surgical procedure may alter the palpebral fissure. Objectives: To investigate the alteration of the palpebral fissure with inferior oblique muscle anterior transposition when it is performed as the sole operative procedure and to report the cases of patients who developed noticeable upper eyelid retraction after inferior oblique muscle anterior transposition preceded by large superior rectus muscle recessions. Methods: The change in the height of the palpebral fissure surgery was evaluated from photographs by 2 masked observers in 3 groups of patients. The control group underwent inferior oblique muscle recession without transposition. The second group (or the insertion study group) underwent transposition of the inferior oblique muscle that was level with the inferior rectus muscle insertion. The third group (or the 2-mm study group) had the inferior oblique muscle placed 2 mm anterior to the inferior rectus muscle insertion. Also, the insertion study and the control groups were evaluated after surgery for bulging and elevation of the lower eyelid on upgaze.

Evaluation of Surgical Strategy Based on the Intraoperative Superior Oblique Tendon Traction Test

“…Bahl reported that IO myectomy is more effective than IO recession [25], Rajavi reported that there is no difference between IO myectomy and IO anterior transposition [26], and Ghazawy reported that IO myectomy has some advantage over IO anterior transposition [27]. The IO anterior transposition procedure is reported to be effective with a single muscle surgery to correct congenital or acquired SOP [28], but it also has serious complications in relation to anti-elevation syndrome [29] or eyelid shape deformity [30]. Lee reported the effectiveness of IO myectomy on unilateral SOP based on the MRI trochlear nerve findings, and concluded that patients without a trochlear nerve showed higher rates of undercorrection and recurrence of ipsilateral hypertropia after IO myectomy than those with a trochlear nerve [31].…”

Inferior oblique muscle fixation to the orbital wall: A profound weakening procedure

“…Recurrent IO muscle overaction (overelevation in adduction) is common and ranges from 15% to 100%, depending on the type of surgery. [1][2][3][4][5][6][7][8][9][10][11][12][13] The mechanism for recurrent or persistent IO overaction varies with the type of surgery. Recession may be insufficient for a markedly overacting IO muscle.…”

“…4 Anterior transposition increases abduction and exclyclotorsion in extreme upgaze creating a Y pattern and overelevation of the contralateral eye. [9][10][11][12][13] Disinsertion may result in unpredictable migration of the insertional fibers toward the original insertion. 4 Myectomy and myotomy may result in recurrent overaction because of the tendency of the IO muscle ends to reunite.…”

“…IO anterior transposition converts the posterior fibers of that muscle segment to a tonic depressor in the primary position and an antielevator limiting upgaze to 30 -35°. 3,9,10 Placing the insertion of the IO nasal to the IR muscle insertion may avoid some of those complications. The IO muscle is parallel to the torsional and horizontal axes of Fick decreasing abduction, exclyclotorsion, elevation in adduction, tonic depression, and antielevation.…”

The pen, the pencil, and the inferior oblique

“…This would explain why the IO muscle brings the entire lower eyelid forward following anterior transposition, a finding not seen with other IO muscle procedures. 15 It would also explain why Quinn and coworkers showed that a 7 mm resection of the distal portion of the IO muscle prior to anterior transposition was no more effective than standard anterior transposition in controlling dissociated vertical deviation. 16 Small primary position hypotropias occurred in a few instances with or without resection and did not occur in any of the five cases where resection with anterior transposition was performed unilaterally.…”