Viagra vision link raises red flag
(CNN) -- U.S. health officials are investigating reports that some men who use Viagra and other impotence drugs are getting a rare form of blindness.
While it has been known for years that users of impotence drugs could experience short-term vision changes, seeing green or blueish hues, what has raised the red flags is the immediacy of the drug's impact and its lasting effect.
In some cases users are getting visual problems within a short time.
"Well, the patient I just described from 1998 noticed the effect within 45 minutes after using the drug. Most of these patients experienced this within hours," says Dr. Howard Pomeranz, associate professor from the University of Minnesota.
Pomeranz co-authored a study in the Journal of Neuro Ophthalmology, which looked at 14 men who experienced vision problems within 36 hours of taking these drugs.
In his research, he noticed not complete blindness, but rather a permanent loss of peripheral vision or a worsening of vision, for example going from 20/20 vision to 20/40.
"We take this seriously," Susan Cruzan, spokeswoman from the Food and Drug Administration, told The Associated Press late last week.
However the FDA and doctors admit there is no proven link.
The numbers are extraordinarily small -- only 38 Viagra users of the more than 20 million who take it have come forward with vision problems.
There have also been four users of another impotence drug called Cialis, the pill's manufacturers say.
They say the vision loss -- known as NAION -- is caused by a sort of stroke affecting the blood vessels of the eye when they become choked off, eventually causing some of the cells in the eye to die.
Interestingly, the number of people who get this same type of stroke is actually about four times higher for people who don't take Viagra, the study's researchers say.
It may be difficult to ever show a link between these medications and visual problems because the people who get the stroke in the back of the eye, are also people with high cholesterol, high blood pressure, diabetes and a history of smoking who are more likely to have erectile dysfunction and take a medication like Viagra.
"You have the same group of patients with the same characterisitcs who might be at risk for this very infrequent condition that affects the eyes," says Michael Berelowitz, Vice President Worldwide Medical of Pfizer.
Still, if you happen to be one who reads those package inserts, you will find reference to erections lasting longer than four hours, painful erections lasting longer than six hours, headache, flushed skin, but you won't find reference to visual loss in there.
Pfizer, Viagra's manufacturer, is talking to the FDA about whether to add it.
It already warns the drug should not be used by men with heart conditions whose doctors have warned them not to have sex.
Also, patients taking drugs that contain nitrates have been warned not to take Viagra because of sudden, unsafe drops in blood pressure.
Still doctors are advising users not to be too alarmed.
"Well, I think there is some concern, but I don't think everyone needs to go running, in panic, to their doctors," says Pomeranz.
If you have ever had a visual problem after taking Viagra or Cialis, talk to your doctor about getting your eyes checked.
CNN's Dr. Sanjay Gupta contributed to this report.
