Congenital absence of the inferior rectus muscle.

A case of unilateral congenital absence of the inferior rectus muscle is presented. Absences of extraocular muscles, either singly or in combination, are rare, but isolated reports have been published. The abnormalities have been reported as occurring with increased frequency in craniofacial dysostoses, notably Crouzon's disease. In the case reported here, the abnormality was discovered during planned vertical muscle surgery for a large left hypertropia. Infraplacement of the horizontal recti was performed at a later date. Computerised axial tomography (CAT) scanning confirmed the absence of the inferior rectus. The embryogenesis of the extraocular muscles is briefly discussed.