A GENE therapy treatment for the most common cause of blindness in young people is being tested on a group of patients in Oxford.
X-linked retinitis pigmentosa (XLRP) is currently incurable and leads to slow and irreversible vision loss.
On Thursday, a 29-year-old man became the first patient to undergo the gene therapy procedure at Oxford Eye Hospital.
The trial, being led by Robert MacLaren, Professor of Ophthalmology at, Oxford University, will use a virus to carry corrective DNA into cells at the back of the eye.
His team hopes to recruit up to 30 patients for the study, which is designed to assess safety and tolerability rather than effectiveness.
To make the treatment work, scientists have to reprogramme a gene called RPGR to make it more stable while not affecting its function.
The instability of RPGR in the retina has previously been a major obstacle to developing gene therapy for the condition.