Inferior oblique anterior transposition for the unilateral hypertropia associated with bilateral inferior rectus muscle aplasia

Bilateral inferior rectus muscle aplasia in the absence of craniofacial abnormality is a rare but possibly under-recognized form of strabismus. Unilateral hypertropia in primary position seems to be a recurrent feature of this condition. We report a case of a 20-year-old woman with left hypertropia in primary position who was found on computed tomography to have bilateral inferior rectus muscle aplasia. A unilateral inferior oblique anterior transposition resulted in correction of the vertical deviation in primary position.