Thanks to gene therapy, people who could previously only detect shades of grey can now distinguish red objects from a darker background
By Jason Arunn Murugesu
10 July 2023
Colour blindness that runs in families, rather than being caused by medication or an underlying condition, has had no treatment
Guido Mieth/Stone RF/Getty Images
A gene therapy has enabled people with a rare type of total colour blindness to faintly see red. In a small trial, those who could previously only detect shades of grey went on to distinguish a red object from its darker background.
Ayelet Mckyton at the Hebrew University of Jerusalem, Israel, and her colleagues studied four people with a rare condition called achromatopsia. Affecting about 1 in every 30,000 to 40,000 people, achromatopsia disturbs the eyes’ cone cells, which are otherwise responsible for colour vision.
The participants, of whom three were adults and one was 7 years old, all had a version of the condition caused by a single genetic mutation. The researchers therefore hoped that inserting working copies of the faulty gene into cone cells would provide some degree of colour vision.
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To test the idea, they injected a virus carrying the correct gene into the subretinal area, home to cone cells, into one eye of each participant. “The virus then enters the cells with the defective gene and corrects it,” says Mckyton.
No major changes were seen in the participants’ vision in the hours after the procedure, but in the months that followed, some reported seeing shades of grey that “glowed” differently to before the injection, says Mckyton.
After carrying out a series of tests, the researchers found that the participants could see red objects against dark backgrounds in their treated eye, when they couldn’t see the colour at all beforehand.