Double-bellied superior rectus muscle.

Congenital variations of extraocular muscles are rare. We report a double-bellied superior rectus muscle, observed in an adult male cadaver aged 70 years. The superior rectus muscle had two equal-sized bellies, which took separate origins from the common tendinous ring and united to form a common belly 1 cm before the insertion. Due to the duplication, the muscle extended laterally beyond the levator palpebrae superioris. Both its bellies were supplied by oculomotor nerve. To the best of our knowledge, this is the first report on doubling of the belly of the superior rectus muscle.