Gene therapy has partly restored the function of the retina’s cone receptors in two children who were born completely colourblind, reported University College London (UCL) researchers.

In two separate trials, four children aged between 10 and 15 years with CNGA3- and CNGB3-associated achromatopsia were each treated in one eye. Six to 14 months after treatment, researchers recorded measurements in two of the children which closely matched those of trial participants with normal vision. “Importantly, this change was paired with a significant improvement in psychophysical measures of cone-mediated visual function,” they said.

Researchers concluded the data show gene replacement therapy in achromatopsia within the ‘plastic period’ of human development can awaken dormant cone-signalling pathways after years of deprivation. "We are still analysing the results from our two clinical trials to see whether this gene therapy can effectively improve everyday vision for people with achromatopsia. We hope that with positive results and further clinical trials, we could greatly improve the sight of people with inherited retinal diseases," said Professor Michel Michaelides from UCL Institute of Ophthalmology and Moorfields Eye Hospital.