Erectile Dysfunction Drug Linked to Vision Problems, Study Finds

A team of Australian researchers found that an ingredient in Viagra may trigger unusual visual responses in those with a common mutation for eye disease.

Sidenafil, sold as Viagra, is used to treat erectile dysfunction problem in men. This oral therapy is also known to have other health benefits that include treating life-threatening heart and lung condition called pulmonary arterial hypertension and benefits people with gastroparesis or delayed stomach emptying.

This drug is also known to have certain detrimental health benefits. Researchers at the University of New South Wales found that an active ingredient called sildenafil present in the erectile dysfunction drug can trigger unusual visual responses in people with common mutation for eye disease and may even have long-term detrimental effect on their vision.

They claim that the ingredient Sildenafil can hinder the functioning of an enzyme that is  crucial for transmitting light signals from the retina to the brain. Based on the clinical trials, it is known that using Viagra in high doses can cause temporary disturbance in the vision of healthy people.

"Side effects can include sensitivity to bright light, blurred vision and altered colour vision," says Dr Lisa Nivison-Smith of the UNSW School of Optometry and Vision Science. "We are concerned that people who have normal vision but who carry a single copy of the mutant gene for the blinding disease, Retinitis Pigmentosa, could be more susceptible to these changes."

In this study, the researchers looked at the effects of single dose of sildenafil on normal mice and mice with a single copy of the mutant gene.  They noticed that there was a temporary loss of visual function in normal mice after being treated with Sildenafil. However, this effect was much greater in the mice with mutation and this response lasted for longer.

They also found early signs of cell death in the eye of the carrier mice and not the normal mice, indicating that the ingredient Sildenafil may trigger degeneration in carriers of retinal disease. This study is significant as 1 in 50 people are likely to be carriers of the recessive genes that trigger retinal disease and remain clueless about this due to the normal vision.

"A better understanding of the effect of this family of erectile dysfunction drugs could help scientists and clinicians plan more successful strategies to account for factors such as a patient's medication and genetic makeup in diseases which cause blindness," says Dr Nivison-Smith.

One of the common genetic diseases leading to blindness is 'Retinitis Pigmentosa' and is caused by a mutation in the gene that produces the enzyme called PDE6. Those with two copies of mutant PDE6 gene get the disease and the carriers with just one have normal vision.

The finding was documented in the journal Experimental Eye Research.