Viagra may cause blindness

WASHINGTON (AP) - U.S. health officials are examining rare reports of blindness among some men using the impotence drug Viagra.

The Food and Drug Administration still is investigating, but has no evidence yet that the drug is to blame, said spokeswoman Susan Cruzan.

This type of blindness is called NAION, or non-arteritic anterior ischemic optic neuropathy. It can occur in men who are diabetic or have heart disease, the same conditions that can cause impotence and thus lead to Viagra use.

The FDA has 50 reports of the blindness. Viagra has been taken by more than 23 million men worldwide.