Resection and anterior transposition of the inferior oblique muscle for treatment of inferior rectus muscle hypoplasia with esotropia

PURPOSE: To report a case of inferior rectus muscle hypoplasia with esotropia, which was treated successfully by resection and anterior transposition of the inferior oblique muscle. OBSERVATIONS: A 1-year-old boy presented with esotropia. He had esotropia of 15-30° and intermittent left hypertropia. At the age of 3 years, the alternate prism cover test showed esotropia of 35Δ and left hypertropia of 25Δ. Magnetic resonance imaging of the orbit revealed left inferior rectus muscle dysgenesis. Strabismus surgery was performed and a hypoplastic left inferior rectus muscle was identified. We performed bilateral medial rectus muscle recession, and resection and anterior transposition of the left inferior oblique muscle. Nine months after the surgery, the patient had esotropia of 8Δ and left hypertropia of 6Δ. CONCLUSIONS AND IMPORTANCE: Resection and anterior transposition of the inferior oblique muscle is useful for hypoplasia of the inferior rectus muscle accompanied by horizontal strabismus.