Published on 05/2/2008

University of Minnesota ophthalmologists say that a condition that causes permanent vision loss has been diagnosed in a small group of men who have taken the erectile dysfunction drug Viagra. The condition, nonarteritic ischemic optic neuropathy (NAION) - sometimes described as "stroke of the eye" - occurs when blood flow is cut off to the optic nerve, which injures the nerve and results in permanent vision loss.

The study, appearing in the Journal of Neuro-ophthalmology, looked at seven men, aged between 50 and 69 years, who had typical features of NAION within 36 hours of taking Viagra for erectile dysfunction. Similar cases have been reported in the past.

"For years, we've known that some men who take Viagra will experience temporary color changes in their vision and see things as blue or green," said Howard Pomeranz, at the University of Minnesota Medical School. "NAION is a much more serious condition because it can lead to permanent vision loss." All of the patients had at least one arteriosclerotic risk factor, including hypertension, diabetes, hypercholesterolemia, or hyperlipidemia. All of the patients also had a low cup to disk ratio, which means that the blood vessels and nerves are tightly bundled together into the small space in the back of the eye.

The researchers believe that ophthalmologists should ask all men with NAION about the use of Viagra, and recommend that patients with a history of NAION in one eye be cautioned that Viagra may increase the risk of NAION in the other eye. "Viagra regulates a chemical in the body to constrict the arteries. This constriction may cut off the blood flow to the optic nerve, especially in people with a low cup to disk ratio, where the blood vessels and nerves are tightly bundled provoking NAION," concluded Pomeranz.

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