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. 

Notes: Dr. M. Kristine Schlossberg

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EditText of this page (last edited February 22, 2010)