For the Color Blind, a Ray of Hope

Researchers use gene therapy to restore color perception in monkeys

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By Randy Dotinga
HealthDay Reporter

WEDNESDAY, Sept. 16 (HealthDay News) -- For color-blind people, new research in monkeys raises the possibility of a world in which they see colors like just about everyone else.

Scientists say they've used a form of gene therapy to eliminate red-green color blindness in monkeys, with no ill effects.

The treatment isn't for the squeamish, and there's no guarantee that it will work in humans. But study co-author Jay Neitz is optimistic.

"The great challenge of finding a way to cure color blindness is solved," said Neitz, a professor of ophthalmology at the University of Washington. "Now, the great problem is transforming this technology so it can be used on humans and be perfectly safe."

An estimated one in 12 men and one in 230 women have some form of inherited color blindness. They have trouble differentiating between some colors because receptors in their eyes lack the ability to perceive the full difference between them. Two percent of men have the most severe form of color blindness.

Color blindness can be inconvenient, leading people to pick clashing colors in clothes or be unable to read graphs and charts. In more severe cases, it can be dangerous. For example, people with red-green color blindness may see the two colors as gray and have trouble distinguishing red from green in traffic lights.

"Those people have a very different color experience than the rest of us," Neitz said. "The biggest challenge is jobs. That's where there's a real headache. You can't be a police officer, fireman, bus driver or pilot if you have red-green color blindness."

Nor, he said, can they be ophthalmologists. In fact, he said, medical students are occasionally disappointed to find that they can't be eye doctors.

There is no treatment for color blindness, although people can wear special glasses or contact lenses to better distinguish between colors.

In the new study, Neitz and colleagues inserted a missing gene into the eyes of red-green color-blind monkeys through an injection. The gene piggybacked on a virus that had been defanged so it no longer caused illness.

The findings appear in the Sept. 16 online edition of Nature.

The researchers then tested the monkeys by measuring their responses to colors. About 20 weeks after the treatment, the monkeys, which are still alive and doing well, were no longer color blind and could distinguish between red and green.

Researchers still need to make sure the procedure is safe for humans, Neitz said. Even if it's 99 percent safe, that's not enough because the eyes are involved, he noted.

Still, "we are confident that something is going to happen," he added.

Anand Swaroop, a senior investigator at the National Eye Institute, is color blind himself and uncertain about whether he'd undergo a treatment to fix the condition, especially considering that he's done fine so far.

"Sometimes if you don't know a color, you just don't know a color. Big deal," said Swaroop, who has trouble distinguishing between light green and light yellow.

"Will I let someone inject something into my eye with some viruses when I can otherwise see normally and I have absolutely no other problem? I'm not sure," he said.

More information

The National Library of Medicine has more on color blindness.

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