KPLU: Scientists Fix Color Blindness in Monkeys (2009-09-16)

Scientists from the University of Washington working on color-blindness have achieved a magical breakthrough. They've given full-color vision to adult monkeys that were born color-blind.

Researchers chose squirrel monkeys because their eyes are so similar to ours. But the male monkeys are all born color-blind, unable to see greens and reds, while many of the females can see the full spectrum. Jay Neitz and his collaborators started on the project more than eight years ago, when he was at the Medical College of Wisconsin.

"It occurred to us, and lots of people that work in vision, that the eye is the ideal place to do gene therapy," he says, because the eye is so self-contained. The idea is to inject genetic material into the back of the eye, to give it instructions it was missing from birth -- on how to make red photo-pigment. Once the genes are in the eye, they start to transform some of the cone cells, and after five months, the monkeys' vision has changed.

How do they know what the monkeys see? "We knew what we'd be up against, convincing the world this worked," says Neitz. "People could question, do they really see like a human sees?"

Neitz says they took the standard test used for checking humans for color blindness (where you try to spot a letter or a number camouflaged in a page full of colored dots). But instead of a letter, they made the hidden object into a blob-like shape, and put the test on a touch-screen.

"From the monkey's perspective, it's like a fruit against a background of leaves. We trained them to touch the screen where they see the color blob," he says. Monkey sees the shape, he touches the screen, he gets a reward. If it's a color he can't see, he stands there, looking agitated, waiting for a blob to appear. After the treatment, Neitz says the two monkeys, Dalton and Sam, seemed excited to be able to spot all the shapes, and get more rewards.

Since these monkeys already had vision, it apparently was easy for the brain to adapt to adding a new set of colors. That's not necessarily the case with full-scale blindness. The work is published in the journal Nature.

There are still safety questions to address before it can be tried in humans. But trials are already underway in Pennsylvania and Florida using this technique, to treat one type of blindness (lebers congenital amaurosis, or LCA). Neitz is an ophthalmology professor and says he gets inquiries every day from color-blind people who desperately want to see the full range of colors.

A monkey performing a color-blindness test. Video courtesy Neitz Laboratory and Nature.com