Researchers from the New York Eye and Ear Infirmary of Mount Sinai (NYEE) report that the man arrived at an urgent care clinic complaining that he had been experiencing a red tint in both eyes and the presence of perceived multicolored flashes of light for two days.

He said that his symptoms had begun shortly after taking a dose of liquid sildenafil citrate—often sold under the brand name Viagra—which he had purchased over the internet.

The substance is known to sometimes cause minor visual disturbances, such as blurry vision or increased light sensitivity, although these typically go away within a day. However, in this case, the patient had ingested far more than the recommended 50 mg dose.