Gene therapy has partly restored the function of the retina's cone receptors in two children who were born completely colourblind, reports a new study led by UCL researchers.

Gene therapy for red-green color blindness may not work in humans as well as it does in the monkeys. Side effects of subretinal injections can include irritation or infection, in addition to the risks of permanent retinal detachment and blindness at the injection site.

There is no treatment for congenital color blindness. It usually does not cause any significant disability. However, there are special contact lenses and glasses that may help.

Scientists cast a rosy light on the potential for gene therapy to treat adult vision disorders involving cone cells -- the most important cells for vision in people. Scientists used gene therapy to cure two squirrel monkeys of color blindness -- the most common genetic disorder in people.