From Daily Mail UK

Five men have gone blind after taking the anti -impotence drug Viagra, a doctor revealed.

It is the first time the medication, taken by millions since its launch three years ago, has been associated with permanent loss of vision.

Howard Pomeranz, director of neuro-ophthalmology at the University of Maryland Medical Centre, said he knew of five males across the U.S. who were diagnosed as having lost their sight after taking Viagra.

The condition, called ischemic optic neuropathy, is caused after blood flow is cut off to the optic nerve in the eyeball.

It usually occurs in those with diabetes, hypertension and other vascular disorders. Viagra, which is available in 100 countries, is known to cause some temporary vision problems such as blue/green colour distortions in certain patients.

Dr Pomeranz said the five men diagnosed with ischemic optic neuropathy after using Viagra had a low cup-to-disc ratio, which is a way doctors measure the small circular indentation where the optic nerve connects to the eyeball.

The low ratio means that the blood vessels and nerves are tightly bundled together into the small space in the back of the eye.

‘We know that Viagra regulates a chemical in the body to constrict the arteries,’ Dr Pomeranz told a conference of the American Academy of Ophthalmology.

‘The constriction may cut off the blood flow to the optic nerve, especially in people with a low cupto-disc ratio, where the blood vessels and nerves are tightly bundled,’ the specialist explained.

‘People who take Viagra who have this particular configuration of their optic nerve at least need to be aware that this is a potential problem that may occur if they use this medication.

‘Whether this is a significant increased risk, I don’t have the statistics to back that up,’ concluded Dr Pomeranz, who called for more research into the matter.

Pfizer, which makes Viagra, strongly denied there was any link and said the drug ‘poses no threat’. A spokesman added: ‘From all clinical experience with Viagra there have been no cases of treatmentrelated blindness reported, and reports of serious visual problems have been extremely rare.’

The men who went blind ‘could have suffered other conditions’. The U.S. Food and Drug Administration, which studies reports of drug side-effects, said it had not received any complaints of sudden blindness in patients who were taking Viagra.

‘We do not have any information on people losing their sight like that,’ confirmed a spokesman.

‘We would take any such reports seriously, and we encourage health professionals to submit any such data to us.’

Leonard Yaffe, analyst with Banc of America Securities, said more information was needed before evaluating what effect the report would have on Pfizer.

‘I’d want to know how often the men were taking the drug and for how long,’ he added. ‘You need to know a lot more than that these men had this problem.’

For more on this story go to: http://www.dailymail.co.uk/health/article-30171/Five-men-blind-taking-Viagra.html#ixzz3FNq1l848

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