A New Cure!?

Until late last year, the idea of a cure for color blindness was a theoretical dream involving gene therapy, which was seemingly beyond our medical abilities. However that may all be changing in the very near future after a study co-authored by Jay Neitz at the University of Washington successfully made an injection of cells into two squirrel monkeys which was a total success!
The monkeys, named Dalton and Sam, both lacked a gene known as L opsin that provides the information for L-Cones in the iris (long wavelength, red sensitive). This is the same cause for red-green color blindness in Humans.

How The Color Blindness Cure Works

As you know, red green color blindness is by far the most common type and is nearly always passed on through defective genetics on the X Chromosome. This defect means that the retina has fewer or none of at least one type of Cone. For healthy color vision all three cones must be present in adequate numbers, or acuity to certain parts of the color spectrum is lost.

One of the monkeys hoping for some juice
One of the monkeys hoping for some juice

The cure is administered by injecting a virus carrying altered genetic information that supplies the missing L opsin gene directly to the retina. Over a period of 24 weeks, the light sensitivity of the cones in the monkeys eyes shifted toward the red spectrum, an area they could not previously differentiate clearly. The adult monkeys received the injection more than 2 years ago and have not yet come to exhibit any side effects.

Summed up in layman’s terms from the original publication online for the journal Nature:


“We’ve added red sensitivity to cone cells in animals that are born with a condition that is exactly like human color blindness,” said William W. Hauswirth, Ph.D., a professor of ophthalmic at the UF College of Medicine and a member of the UF Genetics Institute and the Powell Gene Therapy Center. “Although color blindness is only moderately life-altering, we’ve shown we can cure a cone disease in a primate, and that it can be done very safely. That’s extremely encouraging for the development of therapies for human cone diseases that really are blinding.”


How We Know The Monkeys Are Cured

Co Author Jay Neitz and his Wife, Mauree began training the two squirrel monkeys, Dalton and Sam over 10 years ago. By the time of the injection, Neitz had perfected an adaptation of the Cambridge Colour Test so that the monkeys could tell him which colors they were seeing. Rewards of grape juice were staple during the training!

For nearly 5 months the monkeys showed no change, but then suddenly they were able to correctly identify tests for red and green on the screen. Neitz is not sure what changed, but believes that rather than physical alteration to the neural pathways in the brain, it eventually became able to understand the new information it was receiving.

The prospects for application of this technique may well extend beyond color blindness as mentioned by Neitz:

“…almost every unsolved vision defect out there has this component in one way or another, where the ability to translate light into a gene signal is involved.”


When Can I Get The Color Blindness Cure?

With such exciting results in primates, the research team are pushing toward human trials as fast as possible, but are mindful of the numerous steps involves before the injection will be ready for humans. It is a very promising sign that the monkeys have not exhibited any detectable side-effects in over 2 years, and the virus used to transmit the genetic information, the adeno-associated virus has no record of causing disease in humans. But safety must be conclusively proven before human trials commence.

No time frame has been given, but we can no doubt expect rapid development on the technique – especially given its potentially far reaching applications in curing other forms of more debilitating blindness in the eye. Naturally many researchers involved in vision research have expressed high interest. Sci-fi possiblities may even become reality as speculated by Williams:

“Ultimately we might be able to do all kinds of interesting manipulations of the retina,” he said. “Not only might we be able to cure disease, but we might engineer eyes with remarkable capabilities. You can imagine conferring enhanced night vision in normal eyes, or engineering genes that make photo-pigments with spectral properties for whatever you want your eye to see.”