A possible link has been found between the use of the popular erectile dysfunction drug Viagra and blindness. While the occurrence is rare, experts maintain that it should be made known to the public.

The condition in called NAION or non-arteritic anterior ischemic optic neuropathy. It is most common in men who have heart disease or diabetes and are over the age of 50. They are the same conditions that may cause impotence and therefore lead for the need to take Viagra.

Thus far, the FDA has received 42 reports of blindness which may be related to impotence medication. Thirty-eight of them are from users of Viagra and four by users of Cialis. There is no definite proof that the medication is the cause of the loss of vision.

Pfizer, the company that manufactures Viagra, already admits that a rare side effect can be vision related. On its web site, Pfizer says that a rare and uncommon side effect may be 'Less common are bluish or blurred vision, or being sensitive to light. These may occur for a short time.'

Pfizer and the FDA are now in negotiations to determine if the warning label on Viagra needs to be changed to include the risk of blindness.

'We take this seriously,' said Susan Cruzan of the FDA.

Investers were taking it seriously as well. Pfizer stock was down in early trading on Wall Street as a result of the possible link between Viagra and blindness.