Will Viagra Make You Blind?

(Photo: Reuters/Keith Bedford)Boxes of counterfeit Viagra seized by the U.S. Customs & Border Protection are seen at the agency's offices at John F. Kennedy Airport in New York August 15, 2012.

Will Viagra cause blindness among some who take it? Experts are worried it might. 

An eye doctor who was first to reveal that potential risks associated with the use of erectile dysfunction drug Viagra include blindness was featured in a television show and shared how that risk could be much higher than acknowledged in the FDA-mandated labels.

Dr. Howard Pomeranz, a neuro-ophthalmologist and associate professor at the Hofstra Northwell School of Medicine in New York, spoke to Sharyl Attkisson, the host of "Full Measure," a weekly Sunday news program.

In 2005, he published reports of 14 patients who went blind shortly after taking Viagra. After Pomeranz's investigation, the FDA required labels on Viagra, Cialis and Levitra to add warnings about "permanent loss of vision" from "blood flow blocked to the optic nerve."

When asked about risks, Pomeranz said he tells his patients "there's some research that shows that there is some significant risk of you developing this problem after you take the drug if you're someone who has risk factors for developing this problem."

Attkisson noted that the FDA in 2015 asked three manufacturers at the time to conduct a study to try to evaluate the risk, and Pomeranz told her that only Pfizer has completed it and identified 40 cases of blindness.

Pfizer "calculated approximately a twofold risk of developing Ischemic Optic Neuropathy within a 24-hour period after using Viagra or one of the other similar ED drugs," he added.

Sharyl said her show asked Pfizer if it's fair to say that its own study and label now indicate a link between Viagra and blindness. "Pfizer pointed to the FDA-approved label which says it's not possible to determine whether the cases of blindness are related directly to the drug or other factors. Pfizer also emphasized that the number of patients who go blind is extremely small compared to the number of men who use ED drugs."

But Dr. Pomeranz said the risks could be greater than the 40 cases of blindness Pfizer identified. "I did some research into the FDA adverse events reporting database and found that there are literally hundreds of cases that have been reported to the FDA of Ischemic Optic Neuropathy related to ED drug use. I think it's vastly under reported. There are probably lots of cases out there that we're not even aware of."

Pomeranz said he's not saying people shouldn't use the drug, "but I think people need to be aware that there is a potential risk to their vision if they use one of these drugs."

In a 2014 study, researchers from the University of New South Wales in Australia also found that Viagra may permanently affect the vision of men with eye problems, according to News.com.au, which said they tested sildenafil on healthy mice and on mice with one copy of this mutant gene, and found the healthy mice experienced problems with their eyes for about two days. However, the drug affected the vision of mice who carried the mutant gene for two weeks.