A 6-year-old girl with an intermittent distance exotropia measuring 40 prism diopters with no associated systemic abnormalities underwent corrective squint surgery. Peroperatively, she was found to have an anomalous bifid left medial rectus muscle insertion composed of 2 distinct parallel muscular heads and insertions originating from 1 common origin (Figure).
The narrower superior limb of the bifid muscle measured 3-mm wide and was inserted 5 mm from the limbus, while the wider inferior limb of the bifid muscle measured 5-mm wide and was inserted 5.5 mm from the limbus.
Sundaram V, Chen SDM, Colley S, Hundal K, Elston J. Bifid Medial Rectus Muscle Insertion Associated With Intermittent Distance Exotropia. Arch Ophthalmol. 2005;123(10):1453. doi:10.1001/archopht.123.10.1453