Blindness cure step closer after scientists replace lost light-sensitive cells in back of the eye

A treatment that has helped mice see in the dark could one day restore sight to the blind.

British doctors used injections of healthy cells to repair the damaged eyes of rodents.

The results were dramatic, with small numbers of cells restoring vision up to half of normal levels.

The work is at an early stage but if successful hundreds of thousands of Britons could benefit, such as those with age-related macular degeneration – one of the most common forms of blindness.

University College London researchers took healthy rods – tiny structures in the back of the eye essential for seeing in dim light – from young mice and injected them into the eyes of adult mice whose rods didn’t work.

After four to six weeks, the new rods appeared to be working almost normally and had formed the connections needed to transmit information to the brain.

When the treated mice were put in a dimly-lit pool, they headed straight for the exit.

Untreated mice swam in circles, proving the treated ones could see the way out, the journal Nature reports.

Lead researcher Professor Robin Ali said: ‘Patients who have lost all vision tell me that what they’d really appreciate is a treatment that gives them the ability to see light, to be able to navigate to see the door.’

The British and American scientists say much more work is needed before the technique can be attempted on human patients. The first clinical trials might be five or 10 years away.

But the researchers wrote in the journal Nature: 'The results presented here demonstrate for the first time that transplanted rod-photoreceptor precursors can integrate into a dysfunctional adult retina, and, by directly connecting with the host retinal circuitry, truly improve vision.'

The undeveloped precursor cells used in the study were taken from week-old mice. Up to 32,000 of the cells were integrated into the retinas of recipient animals.

Tests showed that visual responses in the brains of the mice were enhanced after the procedure.

To see how the transplants affected behaviour, mice were placed in a dimly lit Y-shaped water maze in which one of two routes led to escape. This required swimming towards a visual cue, a grating pattern.

After treatment, four of nine night-blind mice completed the task in 70 per cent of trials. Untreated mice, and those given "sham" treatments, performed no better than by chance.

Cell integration in animals that performed best tended to be clustered, rather than spread widely across the retina. This suggested that besides the number of cells, the closeness of the cells to one another might be important.

Professor Phil Luthert, director of the UCL Institute of Ophthalmology, said: 'This is a landmark paper and the techniques used here are part of a pretty big push in regenerative medicine.