Scientists Discover A Genetic Cure For Red, Green Color Blindness

Genetic scientists have discovered a cure for color blindness, offering hope to millions of sufferers.

Scientists at the University of Washington, in Seattle, and the University of Florida restored normal vision to two color-blind monkeys. The technique could prove to be a safe and effective cure for color blindness and other visual disorders related to the cones in the retina.

“Although color blindness is only moderately life-altering, we have shown we can cure a cone disease in a primate and that it can be done very safely,” Professor William Hauswirth, an ophthalmic molecular geneticist at the University of Florida, said. “That is extremely encouraging for the development of therapies for human cone diseases that really are blinding.”

Those suffering from red-green color blindness are unable to distinguish between colors in the green-red-yellow part of the spectrum. This can make reading maps, using the internet and selecting a matching shirt and tie impossible. The disorder affects about 8 per cent of Caucasian males, but fewer than 1 per cent of females.

Normal color vision requires three types of cone in the retina, sensitive to light in the blue, green, and red parts of the spectrum. The squirrel monkeys in the study - Dalton and Sam - lacked a gene called L opsin that codes for the red-sensitive cone. The same gene defect causes most cases of red-green color blindness in humans.

In the study, published Wednesday in the journal Nature, scientists restored normal vision to the monkeys by injecting a virus modified to contain the L opsin gene into the retina. Over 24 weeks the light sensitivity of the cones infected with the virus shifted towards the red part of the spectrum. In a touchscreen test the monkeys were able to discriminate easily between patterns of grey, green and red dots.

The success of the treatment in adult animals demonstrated that the brain is able to rewire itself to take advantage of new receptors. It had been expected that the treatment of congenital vision disorders would only be effective if administered at a young age.

The virus used to deliver the L optin gene, called adeno-associated virus (AAV), is not known to cause disease in humans and has already been approved for use in human gene therapy trials for cystic fibrosis, hemophilia and Parkinson’s disease. Two years on from the color blindness study, the monkeys have shown no adverse effects from the treatment.

Scientists are now looking to obtain permission to begin trials in color-blind humans. “People who are color-blind feel that they are missing out,” Jay Neitz, a professor of ophthalmology at the University of Washington, said. “If we could find a way to do this with complete safety in human eyes I think there would be a lot of people who would want it.”