A case of a slipped medial rectus muscle after strabismus surgery

A slipped muscle after strabismus surgery is a well known complication, but only a few cases have been reported in the medical literature. Here, we report a case of a slipped medial rectus muscle that occurred after strabismus surgery for esotropia.

The patient was a 10 year old male with an acquired esotropia of 20 PD at distance. For treatment, 3.5 mm bilateral medial rectus recessions was performed. There were no complications during the procedure. On postoperative day 8, the eye position was orthotropic in primary position, but a right exotropia was observed in left gaze. The boy was frequently observed rubbing his right eye after surgery. The right exotropia increased to 30 PD 2 months after surgery. Limited adduction of the right eye, a large widening of the lid fissure on adduction, and mild exophthalmos were observed. Based on the above findings, a slipped medial rectus was suspected, and a second surgery, advancement of the right medial rectus muscle was performed 2.5 months after the initial procedure. After this second procedure, the eyes became orthotropic, and the adduction disorder, large widening the lid fissure, and mild exophthalmos resolved.

The slipped muscle may have been caused by insufficient suture and/or excessive rubbing of the eye by the patient. When divergent strabismus is observed after recession of the medial rectus muscle, a slipped muscle should be considered as a differential diagnosis.