Researchers have successfully used gene therapy to help color-blind squirrel monkeys regain their sight.
The development shows offers a new path for treating vision disorders that, until now, were thought to be incurable in adults.
According to a study published online in Nature, a team led by University of Washington visual neuroscientist Jay Neitz targeted two adult male squirrel monkeys missing the L-opsin gene that codes for the L visual pigment, and were thus red-green color-blind.
The scientists injected the monkeys with harmless viruses containing the L-opsin gene and applied an enhancer and promoter into their eyes. After 19 weeks, the monkeys were able to respond to the colors in visual tests.
Red-green colorblindness is a condition that affects almost 10 million American men and a smaller group of women. It is caused by the absence of either long (L)- or medium (M)- wavelength sensitive visual photopigments. The genes coding for these photopigments are found next to each other on the long arm of the X chromosome, considered one of the most variable areas of the genome.
Females with an X chromosome lacking one of these genes are merely carriers of the condition, but sons who who receive the deficient X will be color-blind, otherwise unable to distinguish reds and greens from grays.
In squirrel monkeys, all males are red-green colorblind, but the underlying physiology is the same.
Previously, it was thought that vision could not be altered outside of the critical development stage that takes place at a young age. The team’s discovery could help in treating vision disorders in adults.
Better still, this type of therapy could help pave the way for discovering treatment for more severe vision disorders — so long as retinal degeneration doesn’t set in first.
