[Avulsion of the optic nerve: two case studies]

Avulsion of the optic nerve is a rare and serious injury. The authors report two cases of optic nerve avulsion. The first one concerns a 5-year-old boy who presented ocular trauma after falling on the handlebars of a bicycle. His visual acuity was light perception in the right eye, and his right pupil was unresponsive to light. The anterior segment was normal. The ophthalmoscopic examination showed a total separation of the optic nerve head from the sclera with peripapillary hemorrhage. The second case concerns a 30-year-old man who was hit in the right eye with a stick. On admission, he had no light perception in the right eye, a right afferent pupil defect, a small laceration of the right lower eye lid and no abnormalities on the anterior segment. The fundus examination showed a mild vitreous hemorrhage. Ocular ultrasonography showed vitreous hemorrhage coming directly from the optic nerve head in a mushroom pattern. A CT scan of the orbit revealed a thickened optic nerve. Color Doppler ultrasonography documented slowing of blood flow in the central retinal artery. The two patients received 1 mg/kg/day of prednisone for 2 weeks. No improvement was noted. Optic nerve avulsion is often caused by sudden and forceful rotation of the eye with tearing of the optic nerve as it exits the globe. The nerve can be partially or totally avulsed. The prognosis is usually poor.