Color Blindness
Reviewed by Dr. Michael Fu
What is Color Blindness?
Color Blindness, or Color Vision Deficiency, is an eye condition where a person is not able to distinguish certain colors or shades of colors to some degree. Color Blindness does not mean that a person can only see black and white. A person with color blindness is able to see different colors, however they are not able to see some colors due to deficiencies in the eyes. Color blindness is a hereditary condition but can also be caused by eye diseases, damage to the retina and macula, and aging or when the lens is darkened over time from a cataract. Although there is no absolute treatment for hereditary color blindness, there are methods, techniques, and special glasses that may help people with color blindness differentiate different colors but not truly see them. If you have extreme trouble distinguishing the numbers in one of the pictures below or are not able to see them at all, then you may have some degree of color blindness.
What causes Color Blindness?
The retina contains rods and cones that help us to see objects in different colors and varying degrees of brightness. The cones are photoreceptors that allow us to distinguish between many colors and different shades of these colors as well. The cones contain light sensitive pigments that are particular to range of range of wavelengths. There are three different types of cones with one sensitive to short wavelengths, or the color blue, one sensitive to medium wavelengths, or the color green , and the other sensitive to higher wavelengths, or the color red . When there are deficiencies in the cones, either at birth or acquired through other ways, the cones are not able to distinguish the particular wavelengths and thus, that color range is seen differently. Missing the cones responsible for green and red hues can also affect the sensitivity to brightness. Color blindness is hereditary and thus it is usually transferred at birth. As we age our sensitivity also diminishes as well but usually not to a great extent. Damage to the retina from eye diseases or physical damage may also lead to color blindness.
Types of Color Blindness
Anomalous Trichromacy - A mild shift in the sensitivity of pigments of the cones
- Protanomaly - shades of red appear weaker in depth and brightness
- Deuteranomaly - shades of green appear weaker
- Tritanomaly - very rare case where shades of blue appear weaker
Dichromacy - Great deficiency or missing completely one of the cones
- Protanopia - shades of red are greatly reduced, if present at all, in depth and brightness
- Deuteranopia - shades of green are greatly reduced, if present at all, in depth and brightness
- Tritanopia - very rare case where shades of blue are greatly reduced, if present at all, in depth and brightness
Color Blindness Test
There are a few methods for Color Blindness testing. The most used is the Ishihara plates test. This test consists of plates that contain a circle filled with bubbles in shades of colors to be tested. In this circle is formed certain numbers that people with certain color deficiency will not be able to distinguish. An example is the pictures placed above in the Types of Color Blindness section. To take a color blindness test and get a color scheme of different color deficiency, please visit http://www.colorvisiontesting.com and http://www.iamcal.com/toys/colors/index.php
Viewing the World with Color Blindness
Normal View
Protanope
Deuteranope
Tritanope
The following images were provided courtesy of Terrace L. Waggoner, O.D. More information on color blindness can be found on http://www.colorvisiontesting.com/
[Page updated 12/2010]
