Thousands of people born with a faulty gene which makes them go blind have been offered new hope after a British man underwent the world’s first operation to deliver new DNA to his eyes and restore his sight.
Around 15,000 people in Britain suffer from x-linked retinitis pigmentosa, a deteriorating condition which brings a slow and irreversible loss of vision, and which is the leading cause of blindness in young people.
Loss of sight occurs because a gene responsible for maintaining the light sensitive cells at the back of the eye is missing half of its DNA code.
But scientists can now replace the code using a groundbreaking technique which reprogrammes the gene in the lab, then delivers the healthy DNA into the eye, via a harmless virus.
Last Thursday, a 29-year-old man became the first person in the world to undergo the procedure at Oxford Eye Hospital and is now recovering.
Robert MacLaren, Professor of Ophthalmology at the University of Oxford, who is leading the trial said: "He is doing well and now at home, but we will have to wait a few years to know if it has stopped his retina from degenerating.
“The effect of disease on families with retinitis pigmentosa is devastating and we have spent many years working out how to develop this gene therapy.
“Changing the genetic code is always undertaken with great caution, but the new sequence we are using has proven to be highly effective in our laboratory studies.
“The genetic code for all life on Earth is made up of four letters – G, T, A and C. In retinitis pigmentosa, however, half of the RPGR gene comprises only two letters – A and G.
“This makes the gene very unstable and prone to mutations, making it a lead cause of blindness in patients with retinitis pigmentosa. RPGR is vital for the light sensitive cells at the back of the eye.”
Retinitis pigmentosa affects 1 in 4000 people, with symptoms that typically appear between age 10 and 30. Night vision and peripheral vision go first, as the photoreceptors active in low light – the 'rods' – start to degenerate.
Eventually the condition affects the 'cones' – the photoreceptors responsible for central, detailed, colour vision, causing complete sight loss.
Doctors want to enroll at least 24 more patients in the trial to find out if the technique is safe and effective.