Color Blindness

Most of us take for granted distinguishing the various colors of the rainbow. However, nearly 1 in 25 people may have difficulty assertaining certain colors within the color spectrum. Colorblindness is estimated to be present in nearly 8% of males and in 0.5% of females. 99% of colorblindness involves red and green, only 1% involves blue.

The human retina is made up of what are called Rods and Cones. The rods, located in the peripheral retina, give us our night vision, but can not distinquish color. Cones, located in the center of the retina (called the macula), are not much good at night but do let us perceive color during daylight conditions.

Normal Trichromasy

People with normal cones and light sensitive pigment are able to see all the different colors and subtle mixtures of them by using cones sensitive to one of three wavelength of light -red, green, and blue (normal trichromasy). Genes contain the coding instructions for these pigments, and if the coding instructions are wrong, then the wrong pigments will be produced, and the cones will be sensitive to different wavelengths of light, resulting in a color deficiency.

Anomolous Trichromasy

A mild color deficiency is present when one or more of the three cones light sensitive pigments are not quite right and their peak sensitivity is shifted. These people have deficiency of one of the three colors. Anomalous trichromasy includes protanomaly (red vision weakness) and deuteranomaly (green vision weakness).

Dichromasy

A more severe color deficiency is present when one or more of the cones light sensitive pigments is really wrong. These people do not detect one color of light and are left with two color vision. Dichromasy - includes protanopia (red deficient vision) and deuteranopia (green deficient vision).

Protanomolous Vision
Normal Color Vision
                       
Protanomalous Vision
                       
1% of males have protanamolous vision. This results in difficulty seeing red, orange, yellow, and violet colors. Blue and green remain normal.
 

Protanopic Vision
Normal Color Vision
                       
Protanopic Vision
                       
1% of males have protanopic vision. This results in lack of red vision and shifting of the orange, yellow, and violet colors. Blue and green remain normal.
 

Deuteranomolous Vision
Normal Color Vision
                       
Deuteranomalous Vision
                       
5% of males have deuteranamolous vision. This results in difficulty seeing yellows and greens. Blue, violet, and red remain normal.
 

Deuteranopic Vision
Normal Color Vision
                       
Deuteranopic Vision
                       
1% of males have deuteranopic vision. This results in lack of seeing green and difficulty seeing yellows and blue-greens. Blue, violet, and red remain normal.
 

Colorblindness Tests

Various screening tests exist to try to identify color blind individuals. Here is a quick color test. The top color bar should not appear identical to any of the other bars. If it appears similar in most of the 12 colors to one of the other color bars, you might have one of the color deficiencies described above.
                        Normal
                        Protanomolous
                        Protanopic
                        Deuteranamolous
                        Deuteranopic

Other color vision screening tests:
Shapes Demo Card
Shapes/Numbers Demo Card
Red circle, yellow square card
Red star, yellow circle card