A 10-year-old girl presented with complaints of decreased vision in the right eye for 2 weeks. She visited another hospital and was told she had optic neuritis. Steroid pulse therapy was suggested there, and the patient’s parents wished to consult us for a second opinion. She had a nasal allergy but was otherwise healthy. Family history for hereditary disease was negative. Her best-corrected vision was 6/60 in the right eye and 6/6.7 in the left. She could identify only 1 plate in the right eye and 15 plates in the left eye using the Ishihara test. Intraocular pressure was normal. Slit lamp examination showed normal anterior segments. Relative afferent pupillary defect (RAPD) was found in the right eye. Optic disc swelling with scalloping margins was noted in the right fundus (Fig. 9.1). Fluorescein angiography showed early hypoperfusion around the right optic disc, with mild dye staining on the disc at late phase (Fig. 9.2). A visual field examination showed an inferotemporal defect in the right eye (Fig. 9.3). CT scan showed a tubular enlargement of the right optic nerve without calcification (Fig. 9.4). MRI revealed an enlarged right optic nerve with buckle sign; the tumor was isointense on a T1-weighted image and hyperintense on T2-weighted images (Fig. 9.5).There was only weak enhancement over the optic nerve tumor. These imaging findings were compatible with the diagnosis of optic nerve glioma.