Comparison of Two Surgical Methods for the Treatment of Convergence Excess: Y-Split and Retro-equatorial Myopexy of the Medial Rectus Muscle.

Background: In addition to the bimedial recession of the rectus muscle, two surgical procedures are available to reduce torque: retro-equatorial myopexy (Cüppers-Fadenoperation) and the Y-split of the medial rectus muscle. The aim of this study is to compare the safety and efficacy of the latter two surgical techniques.

Methods: Data from 113 consecutive patients who presented for surgical treatment of convergence excess at the University Hospital of Würzburg between October 2006 and October 2020 were retrospectively analysed. In 2006 - 2014. All patients underwent retro-equatorial myopexy, whereas from 2015 onwards, Y-splitting was the treatment of choice. Orthoptic examinations were performed preoperatively, on the first postoperative day, four months postoperatively and in the longer postoperative course - always with full correction of hyperopia as measured in cycloplegia. The distance and near squint angles in the alternating cover test, the convergence excess and the complication rate as well as the need for repeat surgery were measured.

Results: Both retro-equatorial myopexy and Y-splitting significantly reduced the far and near strabismus angles and convergence excess in all postoperative controls, with no significant difference between the two groups at the four-month follow-up (Levene's variance homogeneity test [far angle p = 0.151; near angle p = 0.114]). The incidence of intraoperative complications and the need for reoperation for over- and undercorrection were slightly lower with the Y-split.

Conclusion: Both retro-equatorial myopexy and Y-splitting of the medial rectus muscle are suitable surgical procedures for the treatment of convergence excess. Y-splitting appears to be safer intraoperatively and easier to learn, due to the absence of retro-equatorial fixation, which is associated with fewer complications. However, revision may be more difficult, this should be considered in the event of loss of information regarding the Y-splitting technique and written documentation of the procedure should always be provided.