Successful Outcomes Of Half-Tendon Width Vertical Transposition For Managing Large V-Pattern Exotropia in Anisometropic Amblyopia

Abstract

Introduction: Strabismus patterns commonly occur among routine strabismus patients, though they are rarely discussed in detail. A or V patterns are found in 15-25% of all horizontal strabismus cases. Managing pattern strabismus can be challenging, as it requires correcting both the horizontal deviation and the vertical pattern. Full-tendon width vertical displacement provides approximately 25 PD of correction and is reserved for extremely large V-patterns but may cause significant torsional changes. Herein, we report a successful surgical outcome of half-tendon width vertical transposition in a case of large V-pattern exotropia.

Methods: A 27-year-old man presented with progressive squinting in his right eye, occasionally involving his left eye, and difficulty focusing with the right eye. A cover test revealed alternate exotropia. V-pattern was diagnosed using Krimsky and PCT tests, showing 50 PD base-in for upgaze, 35 PD for both distance and near, and 25 PD for downgaze, with no movement of the deviated eye. Ocular motility showed no inferior oblique overaction. For patterns >30 PD, full-tendon width transposition is ideally effective in collapsing the pattern. However, there are several complications associated with performing full-tendon width transposition. Therefore, a half-tendon width vertical transposition of the lateral and medial rectus muscles of the right eye was performed. The patient was followed for 6 months postoperatively, and the Hirschberg test showed orthophoria.

Results: In the absence of oblique overaction, the vertical transposition of the horizontal muscle using MALE procedure can be considered for V-pattern exotropia. A half-tendon width vertical transposition with MALE procedure was performed on our patient. The surgical outcome demonstrated orthophoria in all gazes and a successful collapse of the V pattern. No complications like torsion and diplopia were observed in our patient.

Conclusion: MALE procedure with full-width transposition provides greater improvement and is usually reserved for larger V patterns. In our patient, we successfully performed a vertical transposition with a half-tendon width LR recession and MR resection therefore half-tendon transposition can produce favourable outcomes.