A new stem cell treatment has improved vision in patients with a rare genetic eye condition previously considered untreatable, in what researchers describe as a first-in-human clinical trial.

The treatment, developed by researchers at Moorfields Eye Hospital and the UCL Institute of Ophthalmology, was tested in nine patients with aniridia-related keratopathy (ARK), a progressive condition that can cause profound sight loss. The findings have been published in JAMA Ophthalmology.

ARK is caused by a mutation in the PAX6 gene and affects the limbal stem cells found at the border between the cornea and the white of the eye. As the condition progresses, conjunctival tissue grows across the cornea, making it increasingly opaque and gradually reducing vision. The condition is estimated to affect between one in 40,000 and one in 100,000 people.

The researchers developed a collagen scaffold engineered to deliver two types of stem cells — limbal epithelial stem cells and stromal stem cells — to the damaged surface of the eye. In each patient, one eye received the treatment while the other was left untreated as a control.

The treated eyes showed substantial improvements. Patients began the trial with an average ocular surface score of 9.4 in the treated eye, moving to 5.9 after three months and 6.7 after 12 months. By comparison, untreated eyes changed little, starting with an average score of 8.4 and then recording an average score of 8.0 after a year.

Vision also improved by an average of 24 letters on the ETDRS eye test – equivalent to almost five lines on a standard vision chart.

Professor Sajjad Ahmad, consultant ophthalmic surgeon at Moorfields and professor of corneal regeneration at UCL, said the approach was the first optical use of a collagen scaffold containing two types of stem cells. “We are now looking to take this forward to a larger clinical trial, with a view to this being accepted as an NHS treatment,” he added.