Overcorrection after vertical muscle transposition with augmentation sutures in sixth nerve palsy

To report a series of cases, who developed consecutive exodeviation after vertical muscle transposition (VRT) performed for sixth nerve palsy, describe their management and analyse their outcome.

Retrospective case series.

This is an institutional study on patients who developed consecutive exotropia following VRT for sixth nerve palsy in two different centres. The age, gender, cause, and time to surgery were reviewed. Ductions, versions and angles of misalignment were analysed. In those who developed an exotropia >10 PD after surgery, a second surgery was performed. The time to the second surgery, intra-operative findings, surgical procedure and outcome were studied.

A total of 164 cases of VRT for sixth nerve palsy were identified. Nine patients developed consecutive exotropia >10 PD (5.5%). There were no significant differences in the characteristics of those who developed overcorrection compared to those who did not. Five patients had full-tendon muscle transposition, three patients had Hummelsheim procedure and one patient had Jensen procedure. The average angle of consecutive exotropia was 26 ± 9 Δ (range 10-40 Δ). After the second surgery, angle of exotropia decreased to 21 ± 15 PD. Seven patients still had residual exotropia ≥10Δ and the exotropia was corrected in the remaining two patients. The time to second surgery in those two patients was much shorter than the other seven patients.

Patients who undergo VRT should be followed up in the early post-operative period and revisiting the transposition should be done immediately in case of consecutive exotropia to avoid permanent overcorrection.