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Gene Therapy For Colorblindness?

Scientists say they have used gene therapy to enable colorblind monkeys to see red and green, possibly opening the door to curing colorblindness in people.

Jay Neitz of the University of Washington in Seattle and his colleagues injected gene-carrying viruses into the retinas of two male squirrel monkeys, which are naturally colorblind. The gene carried instructions for the production of a protein known as opsin, which makes pigments that are sensitive to the colors red and green.

About five weeks after the treatment, the monkeys -- named Dalton and Sam -- began to develop the ability to see those colors, according to the results of detailed testing reported this week in the journal Nature.

"We knew right away when it began to work. It was as if they woke up and saw these colors. The treated animals unquestionably responded to colors that had been invisible to them," Neitz said in a statement released with the findings.

After more than 18 months of testing, the researchers were able to show that the animals could discern 16 hues, with some of the hues varying as much as 11-fold intensity, the researchers say. The animals continue to see color after more than two years.

The technique could be used to treat humans who are colorblind, including the estimated 3.5 million people in the United States who suffer from the condition, which primarily affects men, they say.

"People who are colorblind feel that they are missing out. If we could find a way to do this with complete safety in human eyes, as we did with monkeys, I think there would be a lot of people who would want it," Neitz said.

The researchers cautioned that much more work will be needed to see if the approach is safe before anyone tries this on people. But the approach potentially could also be used to treat other eye conditions involving damage to the cones in the retina, such as achromatopsia, which causes nearly complete colorblindness and extremely poor central vision, as well as age-related macular degeneration and diabetic retinopathy.

By Rob Stein  |  September 17, 2009; 7:00 AM ET
Categories:  Chronic Conditions , Disabilities , Family Health , General Health  
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Color blindness is a strange affliction, and only a very few people are truly "color blind." I have significant color blindness according to the standard eye tests, and yet have never noticed any problem in daily life. For example, I have red-brown color blindness in that I (so I'm told) cannot distinguish various shades of those colors, and yet see a wide range of reds and browns throughout my daily life. People assume those who have color blindness literally wander a world that is black/grey and white, when actually I can't even tell the difference. The only time it comes up is when I can't see certain numbers in the eye tests themselves. For example, at the top of this very page I see a bright red apple with a vibrant green leaf. In short, for the sake of clarity I would note that many if not most of the 3.5 million "color blind" people in the U.S. are probably just fine without gene therapy.

Posted by: zippyspeed | September 17, 2009 8:25 AM | Report abuse

Rather than color blindness, a better description might be diminished color perception. Unlike zippyspeed, I cannot discern the colors on the apple. The leaf and apple appear different but I could not say with confidence that the colors were red and green. I have learned how to cope with color blindness but it has affected my life in many areas including career choice, traffic signals and selecting clothes to wear. Color blindness gene is recessive in females and dominant in males. All of my brothers are color blind; my children are not. I would volunteer for clinical studies if asked.

Posted by: rtahearn | September 17, 2009 8:54 AM | Report abuse

Zippy Speed:

You are right. Color blindness comes in many shades! But one common thing for all of them is that it is very difficult or even impossible for those "affected" to understand what they are missing, because they just done see it -- pun intended. And the reverse is true too. For normal vision folks, it is always a stretch to imagine how color blind people see the world; although presumably some high-tech filtering device can be developed to mimic the effect of different type of color blindness.

The problem is actually deeper and more phylosophical than that. Leaving aside color blindness for a minute, let's just compare two so called "normal" people. How can one be sure that my red is same as your red, and my green is same is your green. I could be seeing what you call red as green all my life, but just calling it red because that's the name that I was taught to associate with it. As long as I can reliably distinguish the two colors this problem will never come to the surface.

Regarding your assertion that most people are just fine.. I don't know the statistics -- but a friend I knew had trouble with the traffic lights, and he could only distinguish by their relative vertical position (top->red->stop; Middle->yellow; bottom->green->go, and was ruled out of many careers. But still he was not totally color blind meaning seeing the world in black and white.

On a lighter note -- I think men can get away with just primary colors and may be just a few more in between. And this affects primarily men. That's why color blindness is not considered a huge problem.

Posted by: kblgca | September 17, 2009 9:04 AM | Report abuse

Color blindness has been misunderstood by many.

I am the most common "red green" colorblind, a "deutonope" per ophthalmologists, two of my three rods or cones or something are out, but I "see" color! I see beautiful sunsets, I see green grass and blue sky, I can tell you what color my clothes are, (sorting dark socks is another matter but one that can challenge people who aren't colorblind). What I see is what I see, and my brain interprets the world that way.

Here is the best description I can offer of what it's like to be red green colorblind: When I was young and outdoors once with my father, he said, "wow, look at that cardinal in the bush!" I said, "what cardinal?" Surprised, he pointed in frustration, you don't see that? Basically, I found it after a while, and sure enough, there it was, a bright red cardinal in a dark green bush, the difference was it just didn't jump out at me the way I guess it does for most. (After that I got tested and diagnosis confirmed.)

I have no sense, however, of missing out being colorblind, though I, like others I'm sure, have maybe wondered what it would be like, just once, to see how different full color sight is, so this article suggesting it may someday be possible is interesting to read. I wouldn't do anything risky or potentially dangerous just to have that moment, though, things are really just fine the way they are.

Posted by: chris84 | September 17, 2009 9:33 AM | Report abuse

I would like to know if I can add full color vision to only one eye.
I'm saving the other eye for an artificial retina.

Posted by: Crucialitis | September 17, 2009 10:09 AM | Report abuse

My husband is red/green colorblind. I didn't realize what he was seeing until he was holding an Advil and an Ibuprofen in his hand and told me to take the green one! Advil brown was red to him and Ibuprofen brown was green. Which to me is rather sad. We both liked the colors blue and yellow but part of the reason for picking them for our wedding was so he could appreciate it, other than black and white those are the only colors that he can see properly. He's developed a pattern of wearing jeans (because they match anything- his words) and if he has to wear dress pants I have to match the outfits for him- the concept of matching is lost on him. I don't know whether he'd be willing to let someone mess with his eyes, but it would have saved some trouble along the way, including in those electrical engineering classes with the colored wires!

Posted by: cherylot | September 17, 2009 11:56 AM | Report abuse

The implications of this research go far beyond correcting colorblindness. The same methodology, if safe in humans, could correct many nervous system disorders that are due to a single defective gene. The study shows that the adult mammalian nervous system is capable of making the necessary adjustments to use the corrected information. This is an amazing "proof of concept" for genetic engineering in the central nervous system.

Posted by: smf25 | September 17, 2009 2:15 PM | Report abuse

I see lots of colors, but don't always see them the same as other people with "normal" color vision. My wife says taking me to see fall foliage is like taking Ray Charles on a nature walk. I'll say "Look at those beautiful leaves, and she'll say "They're all brown!"
The worst thing is when someone says: It's the house with the green (or brown) roof, and I have no idea which house they're talking about.

Posted by: floridays | September 17, 2009 7:05 PM | Report abuse

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