Chronic relapsing inflammatory optic neuropathy (CRION) is a form of recurrent, isolated, subacute optic neuropathy. A 33-year-old female presented at an outpatient clinic with a pain-ful reduction of vision in the left eye that had developed 10 days earlier. The patient provided a background history of 5 similar attacks over the past 5 years. CRION was diagnosed following ophthalmological and imaging examinations, which revealed optic neuritis without demye-lination. The patient was successfully treated with steroids. The early detection of CRION is important because of the associated risk of blindness if CRION is treated inappropriately.