U of M researcher says Viagra may cause permanent vision loss in some
men

Ophthalmologists at the University of Minnesota 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), 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.
These cases were published in the March 2005 issue of the Journal of
Neuro-ophthalmology. Seven patients, aged between 50 and 69 years, had
typical features of NAION within 36 hours after ingestion of Viagra for
erectile dysfunction. Seven similar cases have been previously
reported.

"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, M.D., associate professor of
ophthalmology 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 is a way doctors measure the small circular indentation where the
optic nerve connects to the eyeball. The low cup to disk ratio means
that the blood vessels and nerves are tightly bundled together into the
small space in the back of the 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," says Pomeranz.

The onset of NAION within hours after ingestion of Viagra in 14
patients supports an association between the use of the drug and NAION.
Based on the fact that 14 cases of NAION have now been reported soon
after the use of Viagra, 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 fellow eye.