Understanding Color Blindness

Stanton Optical Color Blindness Test

Most people are under the misconception that being color blind means only seeing in black and white, but the reality is that there are different types of color blindness that can affect someone. In most cases, color blindness affects men more than women. People who are affected by color blindness have a difficult time being able to differentiate between colors that are obvious to the rest of us.

People Affected by Color Blindness

Color blindness can be inherited, meaning that people can be born color blind. It can also be caused by physical or chemical damage to the eye, the optic nerve, or parts of the brain that process color information. As stated previously, color blindness affects more men (8%) than women (.5%). This happens because the genes responsible for the most common form of color blindness are on the X chromosome. Males only have one X chromosome, and females have 2 X chromosomes, which allows the female X chromosomes to compensate for any loss in the other X chromosome. This is known as X-linked and primarily affects males. When color blindness is inherited it can be present at birth, begin in childhood or not appear until adulthood.

Types of Color Blindness

In most cases color blindness is inherited, and is a result of defects in the genes that contain the instructions for making the photopigments found in cones.

Red-Green Color Blindness

The most common type of color blindness is due to the limited function of the red and green cone photopigments, and is referred to as red-green color blindness. Within the red-green category there are 4 different types known as:

  • Protanomaly: Males with protanomaly have an abnormal red cone photopigment. Red, orange, and yellow appear greener and colors are not as bright. This is considered to be a mild condition and does not affect everyday life. This condition is known to affect 1% of males.
  • Protanopia: Males who suffer from Protanopia, have no working red cone cell. The color red appears black and colors such as orange, yellow, and green will appear as yellow. This condition is known to affect 1% of males.
  • Deuteranomaly: Males who suffer from deuteranomaly, have a  green cone photopigment that is abnormal. In this case, yellow and green appear redder and it is difficult to to tell violet from blue. This condition does not interfere with daily life and is the most common form of color blindness. This is known to affect 5% of males.
  • Deuteranopia: In males with deuteranopia, there are no working green cone cells. Red appears as brownish-yellow, and the color green appears as beige. This disorder only affects 1% of males.

Blue-Yellow Color Blindness

This type of color blindness is considered more rare than the red-green type of color blindness. In this case the blue-cone photopigments are either missing or have very limited function. The two types of blue-yellow color blindness are:

  • Tritanomaly: People who suffer from tritanomaly, have blue-cone cells that are functionally limited. The color blue appears to be greener and it can be difficult to be able to differentiate red and yellow from pink. This condition is extremely rare and can affect males and females equally.
  • Tritanopia: In this case, people with tritanopia, lack blue cone cells. The color blue appears green and the color yellow appears violet or light grey. This condition is also extremely rare, and can affect males and females equally.

Complete Color Blindness

When people are completely color blind, they do not experience any color at all and their visual acuity can also be affected. The two types of complete color blindness are:

  • Cone Monochromacy: This form of color blindness is rare and is a result of failure of two of the three cone cell photopigments.
  • Rod monochromacy or Achromatopsia: This condition is rare, but it is the most severe form of colorblindness. This condition means that none of the cone cells have working photopigments. People who suffer from this condition see the world in black, white and grey and are extremely sensitive to bright environments.

Diagnosing Color Blindness

The most common test used to detect red-green color blindness is the Ishihara Color Test. This test consists of a series of colored circles, known as Ishihara plates.These plates contain a collection of dots in different colors and sizes, and within the circles, the dots form a shape that is clearly visible to those with normal color vision. To people who are colorblind, seeing these patterns will be difficult or almost impossible to see. The outcome of the Ishihara Color Blind test helps diagnose if there is color blindness or not.

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