Regular use of drugs like Viagra, Cialis linked to 3 serious eye conditions: B.C. research

This Monday, Dec. 4, 2017 photo shows a tablet of Pfizer's Viagra, left, and the company's generic version, sildenafil citrate, at Pfizer Inc., headquarters in New York. (AP / Richard Drew)

Researchers in British Columbia say they've found a "strong" link between use of drugs that treat erectile dysfunction and a handful of serious eye conditions.

A study conducted through the University of British Columbia's faculty of medicine suggested the risk of developing three serious conditions increased by as much as 85 per cent for regular users of drugs like Viagra and Cialis.

Those conditions include serous retinal detachment, the collection of fluid behind the retina with no tears or breaks. Those who have SRD experience the sudden appearance of spots or "floaters" in their field of vision and may see flashes of light, UBC said.

Ischemic optic neuropathy (ION) is another of the conditions, in which there is a compromised blood supply to the optic nerve resulting in loss of vision. The third is retinal vascular occlusion (RVO), a condition that results in sudden loss or blurring of vision as well as dark spots due to a blood clot in the veins or arteries of the retina.

Two of the three conditions were already linked to two of the three conditions, the school said in a news release Thursday, but only anecdotally, through case studies.

The latest peer-reviewed research, published in the journal JAMA Ophthalmology this week, was the first large epidemiological study. It confirmed the links, UBC said.

The study involved the health insurance claims of 213,033 U.S. men. These men had no history of the eye conditions in the year before they started regularly using an ED medication, UBC said.

Researchers tracked the men's claims to see how many of them developed the above eye conditions, and how it compared to those who didn't use any ED drugs on a regular basis.

They then factored in statistics on conditions known to be tied to eye problems – such as diabetes and coronary artery disease – and found that ED medication users were 2.58 times more likely to develop SRD.

They were 2.02 times more likely to experience ION, according to their insurance claims, and 1.44 times more likely to develop RVO.

"These are rare conditions, and the risk of developing one remains very low for any individual user," Mahyar Etminan said in the UBC statement.

But, the associate professor in the school's ophthalmology and visual sciences department went on, given an estimated 20 million prescriptions are doled out each month in the U,S., it could still impact a significant number of people.

"Regular users of these drugs who find any changes in their vision should take it seriously and seek medical attention," Etminan said.

Of the men in the study, there were a total of 1,146 cases, more than half of which involved RVO.

There is currently no proof that the drugs actually cause the conditions, just a statistical association.

As for the reason behind what researchers called a "strong" link, Etminan said, it could be due to the medications' impact on blood flow.

The drugs work by improving blood flow. As described by the U.S.-based Mayo Clinic, the drugs reverse ED by "enhancing the effects of nitric oxide, a natural chemical your body produces that relaxes the muscles in the penis. This increases blood flow and allows you to get an erection in response to sexual stimulation."

But it's also known, according to Etminan, that drugs like Viagra, Levitra, Staxyn and Cialis can hinder blood flow to other parts of the body.

"So although our study doesn't prove cause-and-effect, there is a mechanism by which these medications could conceivably lead to these problems," the associate professor said.

The ION risk is known from other research, but the possible risk of the conditions SRD and RVO are not addressed in the information given to patients, UBC said.

Etminan said he hopes his team's research will raise awareness of all the potential side effects, and that patients will then let their doctors know if they note any visual changes.

Other possible side effects of oral ED medications include flushing, headache, indigestion, stuffy or runny nose, back pain and, again as described by the Mayo Clinic, "visual changes, such as blue tinge to vision, sensitivity to light or blurred vision." 

Those side effects are rare, the clinic said. Even more rare, but still possible, are hearing or vision loss and priapism, or "an erection that doesn't go away on its own."

The study was conducted from data in the PharMetrics Plus database between Jan. 1, 2006, and Dec. 31, 2020.