[Visual impairment due to rare optic nerve tumor].

A 49-year-old male patient presented with acute symptoms of reduced vision and relative afferent pupillary defects. Static perimetry testing revealed severe visual field defects and the diagnosis of neuritis of the optic nerve was suspected. A magnetic resonance imaging (MRI) scan was performed and showed an intraocular right-sided semicircular mass around the optic nerve which was partially calcified in computer tomography (CT). The diagnosis of an optic nerve sheath meningioma was made. The visual acuity and visual field defects improved under therapy with prednisolone. Therapeutic options were discussed in an interdisciplinary board but no intervention is planned so far and only regular follow-up controls have been arranged.