Imagine a sunflower that’s slightly blue. Or a stop sign that’s not red. These may be everyday sights for a person who's color blind—which means they perceive wavelengths of light differently than most people.
“Color blindness is usually inherited,” says Jessica Lattman, MD, a New York City-based ophthalmologist. Several genes are needed to make the color-detecting molecules, or photopigments, in the cone-shaped cells of the retina (known as cone cells). Abnormalities in those genes can lead to difficulty seeing reds and greens, or blues and yellows—or in rare cases, an inability to see any color at all.
“Because most forms of the disorder are linked to the X chromosome, [it] affects men far more commonly than women,” says Dr. Lattman. It's estimated that 8% of men and just 0.5% of women of Northern European descent have the common type, red-green blindness.
While there’s no cure for color blindness, treatments do exist: “Some people find that wearing tinted glasses helps them detect colors better," Dr. Lattman says. "And there are actually smartphone apps now that allow people to take a picture of something and be informed of what color it is.”
To show how color blindness can affect a person's view of the world, the UK site Clinic Compare created the eight GIFs below. Each one portrays a different type of the disorder.
Red-Green Color Blindness
Red-weakness—in which reds, oranges, and yellows appear greener and less bright—doesn't tend to interfere with a person's daily life. About 1% of men have this mild, X-linked type, according to the National Eye Institute.
Also affecting about 1% of men, red-blindness means red appears back; and shades of orange, yellow, and green may register as yellow.
Green-weakness is the most common form of color blindness, says Dr. Lattman. Five percent of men have it. To them, yellow and green appear redder; and blue and violet look the same.
With this X-linked type affecting 1 in 100 men, greens appear beige; and reds look brownish-yellow.
Blue-Yellow Color Blindness
"Tritantomaly is very rare," says Dr. Lattman, "and it affects both men and women equally." A blue-weakness, this form of color blindness makes blue appear greener. It also makes it tough to differentiate yellow and red from pink.
Blue-blindness is extremely rare, and also occurs in both men and women. People with tritanopia see blue as green; and yellow as violet or light grey.
Complete Color Blindness
There are three types of photopigments—red, blue and green. But in people who have cone monochromacy, two of the three aren't functional. People with blue cone monochromacy (shown above) are often also near-sighted and have reduced sharpness in their vision, says Dr. Lattman.
Red monochromacy (achromatopsia)
In people who have monochromacy, the most severe type of color blindness, none of the photopigments are functional. "These people see the world exclusively in black, white, and grey," Dr. Lattman says. They also tend to be very sensitive to bright light.