Surgical management of iatrogenic medial rectus transection following functional endoscopic sinus surgery: a report of two cases.

INTRODUCTION: Functional endoscopic sinus surgery (FESS) is a widely used procedure for chronic sinusitis. Although it is generally considered a safe procedure, serious ophthalmic complications might occur. In this report, we discuss the results of Foster augmented full tendon vertical muscle transposition (VRT) with and without resection for two cases presented with iatrogenic complete medial rectus transection following FESS.

METHODS: Case 1: A 43-year-old female presented with significant left eye motility limitation after FESS. Examination revealed left very large-angle exotropia 60 prism diopters (PD), severe limitation in adduction of -4, and MRI confirmed medial rectus muscle transection. The patient underwent left eye Foster augmented full tendon vertical rectus transposition (VRT), followed by maximum left lateral rectus muscle recession with Botox injection. Case 2: A 31-year-old male presented with diplopia and left eye motility limitation following FESS. On examination, there was a large angle exotropia of 40 PD, hypotropia of 20 PD, and limitation in adduction of -4 in the left eye. Imaging showed medial orbital wall injury and complete medial rectus transection. He underwent Foster augmented full tendon VRT surgery with resection.

RESULTS: Case 1: Over 3 years, alignment stabilized at 25 PD exotropia with improved adduction -2, no diplopia in the primary position. Case 2: Postoperatively, the patient achieved orthophoria and no diplopia in the primary position, maintained for 1 year of follow-up.Discussion: Early recognition of medial rectus injury and appropriate selection of surgical techniques are essential to optimize ocular alignment and reduce diplopia. These cases illustrate that Foster augmented full tendon VRT, with or without resection, can provide meaningful functional and cosmetic improvement in patients with iatrogenic medial rectus transection.