Viagra
Viagra could be linked to eyesight problems and blindnessMark Blinch/Reuters file photo

Viagra could cause blindness in some men with eye problems, according to a new study.

Australian researchers have found the anti-impotence drug could cause permanent damage to those suffering from retinitis pigmentosa, a rare hereditary condition, and worsen the eyesight of those with normal vision.

One in 50 people are prone to genes which lead to the degeneration of cells in the retina - the area of the back of the eye which detects light.

Viagra, once the fastest-selling drug in history, is now thought to be linked to obstructing an enzyme that is important for transmitting light signals from the retina to the brain.

Scientists from the School of Optometry and Vision Science at the University of New South Wales, tested the ingredient Sildenafil found in the erectile-dysfunctional drug on healthy mice, which had eye problems for two days. The vision of mice carrying the mutant gene was affected for two weeks.

Those mice carrying the defective gene also showed early signs that cells in their eyes were dying.

Dr Lisa Nivison-Smith from the university, said: "If cells actually die in the retina that would lead to blindness."

The findings have been published in the Experimental Eye Research journal.

It follows news Britain can expect a Viagra boom after its cost plummeted by 93% as cheaper products have become available.