Anomalous separation of the medial rectus muscle, abnormal separation into superior and inferior compartment, and surgical management

We describe a case of an anomalous separation of the medial rectus muscle in an 18-month-old female undergoing strabismus eye muscle surgery for partially accommodative esotropia. During surgery and after hooking the medial rectus muscle, it was noted that the width of the muscle tendon was shorter than usual and that the muscle insertion was displaced inferiorly, this prompt further exploration. It was found that the medial rectus muscle had an anomaly were it was seperated into two (superior and inferior) compartments which were 5 mm apart. This finding may further suggest the compartmentalization theory of the horizontal rectus muscles where the muscle is separated into two nonoverlapping superior and inferior zones, each working independently of the other. In this report, we present the case and suggest surgical technique that can be utilized to address this abnormality, along with the postoperative results.