If you are color blind, you have difficulty distinguishing between colors– usually red and green or blue and yellow – but it would be unusual if you could see no color at all. A more formal term for color blindness is “color vision deficiency” or CVD. The colors that you see or don’t see as a color blind person depend on the type of color blindness that you have.
Color blindness is an often misunderstood condition. Many assume because of its name that “color blind” means a person can only see in black and white. In actuality, the vast majority of people with color blindness do see color, but they see a much narrower range of color than a person with normal vision. It is estimated that a person with normal color vision can see up to one million distinct shades of color, but a person who is color blind may see as few as just ten thousand colors (1% of the normal range).
Color blindness is caused by a change or reduction of sensitivity of one or more of the light-sensitive cone cells in the eye. The human eye contains millions of cone cells which work together to translate light into neural signals that are transmitted along the optic nerve to the brain, resulting in the sensation of color vision. The most common type of color vision deficiency is called “red-green color blindness”which occurs when the green and red sensitive cone cells’ sensitivities overlap more than they are supposed to. Instead of seeing green and red as distinct colors, the person sees them as being very similar, thus the resulting color confusion and other frustrations.
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Color blindness or color vision deficiency (CVD) includes a wide range of causes and conditions and is actually quite complex. Usually when people talk about color blindness, they are referring to the most common forms of red-green color blindness, which are genetic conditions caused by a recessive gene on the X-chromosome, but there are other types as well. The types of color blindness are summarized below. For additional information visit our Types of Color Blindness section.
Protan Color Blindness
Protans, people with Protanomaly, have a type of red-green color blindness in which the red cones are not absent but do not detect enough red and are too sensitive to greens, yellows, and oranges. If you are a protan, greens, yellows, oranges, reds, and browns may appear similar, especially in low light. Red and black might be hard to tell apart, especially when red text is against a black background. As a Protan, you may have never seen the color purple or the color pink because seeing the red component in purple or pink is so suppressed that you can view only the blue component of the color purple or the white component of pink. As a result, you often can’t tell the difference between blues and purples, or pinks and grays.
Deutan Color Blindness
Deutans, people with Deuteranomaly, have a type of red-green color blindness in which green cones are not absent but do not detect enough green and are too sensitive to yellows, oranges, and reds. If you are a Deutan, greens, yellows, oranges, reds, and browns may appear similar, especially in low light. It can also be difficult to tell the difference between blues and purples, or pinks and grays.
Tritan Color Blindness
Tritan color deficiency is most commonly acquired later in life due to aging of the eye or medical complications. If you are a Tritan, you have reduced sensitivity in you blue “S” cone cells, which can cause confusion between blue versus green and red from purple. Cataracts, glaucoma and age-related macular degeneration could cause you to test as a Tritan. In extremely rare cases tritanopia can be inherited.
Monochromacy and Achromatopsia
Rod-Monochromacy, S-cone Monochromacy and Achromatopsia are rare vision deficiencies that include partial or complete color blindness. Achromatopsia is also known as “complete color blindness” and is the only type that fully lives up to the term “color blind”. It is extremely rare, however, those who have achromatopsia only see the world in shades of grey, black and white. In some cases low vision disorders such as progressive cone dystrophy can cause a gradual deterioration of color vision that eventually turns into complete achromatopsia.