Erection pills are associated with a higher risk of eye defects, a new study suggests, although there seems no need to sound the alarm about this.

An estimated 150,000 Dutch people use Viagra, mainly to combat erectile dysfunction. Quite a few, so you want to know exactly what the side effects are. For example, the chance of various eye defects would be greater if you use Viagra, or one of its lesser-known competitors. However, this connection has never been thoroughly investigated. One new big study is trying to change that.

Detaching retina

For their research Mahyar Etminani from the University of British Columbia and colleagues PharMetrics Plus, a huge US medical database. Between those dates, they found more than 200,000 men who had just started taking so-called PDE5I-medication. In other words: with one of the ‘erection pills’ Viagra (sildenafil), Levitra (vardenafil), Cials (tadalafil) or Stendra (avanafil).

In these individuals, the researchers looked at whether they were more likely to have three eye abnormalities: retinal detachment† blood vessel occlusion in the retinaor occlusion of the optic nerve’s blood supply† The subjects who took one of these drugs were 1.41 to 2.42 times more likely to develop one of these conditions, compared to subjects who did not.

Underlying cause

Now that sounds like a significantly increased risk, says Maarten van Smeden, medical statistician and epidemiologist at UMC Utrecht. “But you have to keep in mind that these are very rare disorders. You would have to follow a hundred men taking Viagra for ten years to find one or two of these eye disorders.” In other words: a small chance of a side effect times two is still a small chance.

Furthermore, it does not have to be the case that Viagra actually causes eye defects. For example, it is quite conceivable that someone suffers from a condition that entails erectile dysfunction and eye problems.

The researchers consider four such possible underlying causes: high blood pressure, certain heart complaints, diabetes and smoking. “But why did the researchers opt for those complaints?” Van Smeden wonders. “They describe that very briefly in their article.”

In addition, there may be measurement errors in the database used where these complaints are concerned. The researchers dismiss it, but Van Smeden disagrees. “It could well be that the chance of an eye abnormality is either a lot greater or a lot smaller if the measurement errors had been smaller.”

Carefully formulated

All in all, Van Smeden still sees a lot of uncertainties. “I don’t think it’s necessary to sound the alarm in response to this study.”

The researchers themselves also formulate their conclusion very carefully. “The findings of this study suggest that frequent use of this medication carries an increased risk of the examined eye disorders could be bring.”

However, Etminan and colleagues do advise users of Viagra and the like to contact their doctor if they experience eye problems. But, Kevin McConway, professor emeritus of applied statistics, says on the site Science Media Center: “I think that’s good advice for everyone – whether they’re taking this kind of medication or not.”