The active substance in Viagra, sildenafil, can cause permanent visual disturbances, Australian researchers suggest. This severe side effect can occur in a small number of blue pill users. Who is at risk?
The problem concerns owners of a genetic mutation that causes retinitis pigmentosa. This vision loss disease is associated with a build-up of a pigment in the retina, with impaired circulation within the retina and loss of retinal cells.
One of the factors causing it is the gene encoding the PDE6 enzyme. However, the disease only develops in people who have two copies of the gene. People with one copy maintain normal eyesight and are most often unaware that they have a mutation.
As observed by researchers at the University of New South Wales in Sydney, sildenafil blocks an enzyme that is involved in transporting light signals from the retina to the brain. Previous studies on the drug show that it may cause short-term, transient visual disturbances in healthy people (hypersensitivity to bright light, blurring of the image or disturbances in color perception).
Observing the effects of sildenafil on mice with a single copy of the pigment retinopathy gene and controls, the researchers noted that all rodents developed visual disturbances, but those with the single copy of the mutation were more severe and lasted longer. Moreover, early signs of degenerative changes in the retina were seen in single-copy mice.
Sources: UNSW / Experimental Eye Research / Money.pl