Is it red or green? Interesting Facts about Color Blindness

Most of us share a common color vision sensory experience. Some people, however, have a color vision deficiency, which means their perception of colors is different from what most of us see.

Color deficiency occurs when you are unable to see colors in a normal way. Most commonly, color deficiency (also known as color blindness) happens when someone cannot distinguish between certain colors, usually between greens and reds, and occasionally blues.

Inherited color deficiency is caused by abnormal photopigments. These color-detecting molecules are located in cone-shaped cells within the retina, called cone cells. In humans, several genes are needed for the body to make photopigments, and defects in these genes can lead to color deficiency.

There are three main kinds of color deficiency, based on photopigment defects in the three different kinds of cones that respond to blue, green, and red light. Red-green color deficiency is the most common, followed by blue-yellow color deficiency. A complete absence of color vision —total color blindness – is rare.

Can you see the numbers in these two images? If not, you might be color blind. 

Up to 8 percent of men and 0.5 percent of women with Northern European ancestry have the common form of red-green color deficiency. (That's about 1 in 12 men and 1 in 200 women.) 

Men are much more likely to be colorblind than women because the genes responsible for the most common, inherited color blindness are on the X chromosome. Males only have one X chromosome, while females have two X chromosomes. In females, a functional gene on only one of the X chromosomes is enough to compensate for the loss on the other. This kind of inheritance pattern is called X-linked, and primarily affects males. 

In 2012 a type of sunglasses called EnChroma were invented that actually boost the saturation of red and green light. That helps to improve color vision in people with red-green color deficiency, the most common form.

In addition to the glasses, there are iPhone and iPad apps, for example, that help people with color deficiency discriminate among colors. Some of these apps allow users to snap a photo and tap it anywhere on the image to see the color of that area. More sophisticated apps allow users to find out both color and shades of color. These kinds of apps can be helpful in selecting ripe fruits such as bananas, or finding complementary colors when picking out clothing.

While these glasses don't cure colorblindness, they have inspired more research into future cures through gene therapy. One study involving gene therapy in male squirrel monkeys (who are all born red-green color blind) showed promising results. The researchers injected the red photopigment gene into the retinas of male monkeys born without it. The gene was targeted to green cones and allowed those cells to respond to red light. The monkeys were able to see with full three-color (trichromatic) vision. This shows that even though the monkeys’ red cones had been absent from birth, the brain circuitry for detecting red was still in place—offering hope that a similar approach could help people who’ve been colorblind since birth.  

Sources: 

National Eye Institute. nei.nih.gov

EnChroma.com

MIT Technology Review. https://www.technologyreview.com/s/601782/how-enchromas-glasses-correct-color-blindness/

American Academy of Ophthalmology. aao.org