Color Blindness: What It Really Means
Hearing "color blind", many people picture a black-and-white world. That only applies to one very rare form. Most color blind people do see colors – just differently. Here is an overview of every type.
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Color blind or color deficient?
In everyday language, "color blind" is used for any color vision problem. Eye doctors distinguish:
- Color vision deficiency (anomalous trichromacy): all three cone types are present, but one responds differently. Colors are seen, certain shades are harder to tell apart. This is the most common form.
- Dichromacy ("-anopia"): one cone type is missing, so the world is seen with two instead of three primary colors.
- Total color blindness (achromatopsia): no colors, only shades of light and dark. Very rare.
Types of color blindness
| Type | Cones affected | Typical confusions | Frequency |
|---|---|---|---|
| Deuteranomaly / deuteranopia | green (M) | red–green, brown–green, pink–gray | about 6% of men |
| Protanomaly / protanopia | red (L) | red–green, red looks dark | about 2% of men |
| Tritanomaly / tritanopia | blue (S) | blue–green, yellow–pink | rare |
| Achromatopsia | all cones | no colors | about 1 in 30,000 |
The first two rows together are called red-green color blindness and make up the vast majority of cases.
What causes color blindness?
Most types are inherited. Red-green color blindness is passed on via the X chromosome, which is why it is much more common in men. Blue-yellow color blindness and achromatopsia are inherited differently and affect men and women about equally.
Color blindness can also be acquired: through glaucoma, diabetic eye disease, macular degeneration, optic nerve inflammation or certain medications. The natural yellowing of the lens with age also shifts color perception slightly toward blue-yellow.
How to test for color blindness
A good first step is a plate test based on the Ishihara principle. Our free online test screens for red-green color blindness and estimates whether it is protan or deutan. An eye doctor makes the diagnosis.
Living with color blindness
Color blindness is not a disease in the usual sense and – except in achromatopsia – does not affect sharpness of vision. Color filters on your phone, color-identifier apps and color blind friendly design help. For red-green color blindness, color blind glasses can improve contrast.
By the way: many animals are "color blind" in the human sense too – see what colors can dogs see? and what colors can cats see?
Frequently asked questions
Do color blind people see in black and white?
Only people with the very rare achromatopsia. Everyone else sees colors but confuses certain shades.
What is the difference between color blindness and color deficiency?
With a color deficiency all three cone types are present but one works differently. With dichromacy one cone type is missing.
Can women be color blind?
Yes, but less often. About 0.5% of women have red-green color blindness; blue-yellow color blindness and achromatopsia affect men and women equally.