ABSTRACT
We report a 56-year-old man who suffered from acute unilateral visual loss that was revealed by magnetic resonance imaging (MRI) to be optic perineuritis with subtle involvement of perineural fat. Visual evoked potentials (VEPs) were flattened in the left eye, but normal in the right eye. Following diagnosis of optic perineuritis, intravenous methylprednisolone was administered for 3 days. Two weeks later, visual acuity in the left eye was improved, and abnormal MRI images were completely resolved together with normalisation of VEPs. We conclude that VEPs may be helpful in confirming this type of disease restricted to the optic nerve sheath with subtle perineural involvement.