Medial rectus disinsertion for management of chronic complete sixth nerve palsy

Purpose To report the outcomes of the medial rectus (MR) disinsertion procedure for the management of refractory esotropia (ET) with or without Abnormal head posture (AHP) in chronic complete sixth nerve palsy. Methods This is a retrospective case series of patients with sixth nerve palsy who suffered from residual ET and diplopia following the conventional strabismus surgeries and underwent MR disinsertion procedure between April 2017 and February 2020. This procedure was offered to the patients who declined to use prism and did not wish to perform surgery on the fellow eye. The demographic and clinical data, including sex, age, visual acuity, pre and postoperative angle of strabismus, duction limitations, results of forced duction and force generation tests, details of prior strabismus surgeries, orbital CT scan findings, and follow up duration were collected from the medical records. Results Six patients were enrolled in this study. Mean age was 35.0 +/- 14.0 years, and mean follow-up was 15.3 +/- 5.9 months. The ET at the Primary position (PP) was 35.0 +/- 18.4 prism dioptre (PD) before MR disinsertion, which decreased to 14.2 +/- 17.4 PD after MR disinsertion procedure. Four cases needed additional complementary surgeries to improve residual ET in PP. No case developed overcorrection. Abduction deficiency was -5.0 +/- 1.3 before MR disinsertion, which improved to - 2.8 +/- 0.5 units at last follow-up. The mean of induced adduction deficiency was - 2.9 +/- 0.4 at last follow-up. Conclusions MR disinsertion can be considered in patients with chronic complete sixth nerve palsy and refractory diplopia when the conventional methods have failed.