An eye for an eye, a tooth for a tooth.

A 77-year-old man presented with the complaint of a painless decrease in vision in both eyes for 1 year. He underwent bilateral cataract surgery without improvement. Neuro-imaging and genetic testing for mitochondrial disease was negative. Examination was consistent with a diagnosis of toxic-nutritional optic neuropathy. On further questioning the patient admitted chronic ingestion of mouthwash 3 times daily in the past 18 months after completion of dental work. After discontinuation of mouthwash ingestion, visual acuity and fields improved. This case shows how chronic ingestion of mouthwash can lead to a bilateral toxic optic neuropathy, even in the absence of other risk factors.