In light of recent reports from researchers at the University of Minnesota that claim that Viagra causes NAION or non-arteritic anterior ischemic optic neuropathy, Pfizer Inc., the pharmaceutical manufacturer of the world's most used treatment for erectile dysfunction, claims that there is no conclusive proof that Viagra indeed causes blindness.

A spokesperson for the pharmaceutical giant however did confirm that the drug maker was in discussions with the US Food and Drug Administration about adding a disclosure to Viagra's label which said that in rare cases men taking this drug had developed blindness. The spokesperson further went on to add that men who take Viagra often have high blood pressure, diabetes and high cholesterol, which are also associated with the conditions that can cause NAION.

The report that Viagra may cause NAION was first brought to light by Dr. Howard Pomeranz, MD an eye specialist in 2000, when he initially reported the case of a man who developed NAION soon taking Viagra. Since then several other cases of NAION have been reported after the drug has been taken. In a study published by Dr. Pomeranz recently, he noted seven new cases of this disease this past March, bringing a total of 14 men developing NAION possibly because of Viagra. Meanwhile the FDA also confirmed that they were investigating similar reports in approximately 50 men.

While Pfizer does admit that some Viagra users have reported loss of vision, the company still asserts that there is not enough verification to support the claim of Viagra causing blindness. Pfizer does maintain however that Viagra causes some vision issues that are not common but do occur, such as bluish or blurred vision, or the sensitivity of the eyes to light. While Pfizer is considering changing its warning label, the company is still not ready to admit that Viagra may cause blindness.

seven years. Though Viagra has received the most reports of blindness in men taking impotence drugs, other impotence drugs in the market such as Levitra and Calias have reported a few cases of blindness or NAION.

According to Pfizer, outside of Viagra's clinical trials the reports of extreme visual loss have been very rare due to NAION. Those who have bad eyesight have the highest chance for developing NAION according to experts. People who have diabetes, hypertension or high cholesterol are also at a greater risk for NAION as well. Additionally none of these systematic disorders are firmly associated with this eye disease, while diabetes accounts for only a minority of the cases. This disease can be extremely disabling, especially if both eyes are affected. And since there is no successful treatment for this eye problem, NAION is can be severely disruptive to a person's life.

With things still up in the air about Viagra conclusively causing blindness, its parent company Pfizer is standing firmly behind the drug and its effectiveness.