A 7-year-old boy presented to us with a sudden bilateral decrease in visual acuity. At the age of 4 months bilateral congenital glaucoma had been diagnosed and trabeculotomy performed. Eye pressure and fundus were monitored regularly. Both magnetic resonance imaging and computed tomography revealed a giant supraclinoid aneurysm originating in the right internal carotid artery. After comprehensive examinations endovascular balloon occlusion of the internal carotid artery was performed in conjunction with extracranial-intracranial bypass to augment the insufficient circulation.