A 42-year-old male patient was operated on for a giant fusiform aneurysm of the right internal carotid artery. Extracranial-intracranial bypass was first performed. Despite suction decompression, the aneurysm could not be clipped for its fusiform neck, and it was coated with surgical gauze. Before surgery, his bilateral visual acuity was 1.0; there was a complete left homonymic hemianopia, the fundus oculi was normal. On postoperative day 1, the visual functions were unchanged. Then there was a visual loss in the right eye that progressed to blindness 2 weeks after surgery. The authors consider variants of the pathogenesis of blindness: 1) development of foreign-body granuloma and surgical gauze-induced optochiasmal arachnoiditis; or 2) thrombosis of the aneurysm and thickening of its wall with compression of the right optic nerve. One-year follow-up revealed that the visual acuity of the right eye recovered (1.0), but the right optic disk became pale, the left optic disk was normal. A complete left homonymous hemianopia was unchanged. Spontaneous recovery of visual acuity makes the second hypothesis of the pathogenesis of blindness more preferable.