A review of 103 Viagra clinical trials involving 13,000 patients found no reports of non-arteritic anterior ischemic optic neuropathy (NAION). Outside of clinical trials, Viagra has been used by more than 23 million men worldwide over the past seven years and reports of visual field loss due to NAION are extremely rare, stated Pfizer Inc in a press release.

The company was responding to the recent US FDA reports that they had received more than 40 reports of a type of blindness in men taking impotence drugs, especially Pfizer's Viagra.

There is no evidence showing that NAION occurred more frequently in men taking Viagra than men of similar age and health who did not take Viagra. NAION is the most common acute optic nerve disease in adults over age 50 and it shares a number of common risk factors with erectile dysfunction: age over 50, high blood pressure, high cholesterol, diabetes. Most of the reported cases in which NAION has occurred in men taking Viagra have involved patients with underlying anatomic or vascular risk factors associated with the development of NAION, the release added.

Pfizer is in discussions with the Food and Drug Administration to update the Viagra label to reflect these rare ocular occurrences.

Viagra has a strong safety profile and remains an effective medication that benefits millions of patients.