The term “color blindness” is somewhat misleading. The vast majority of individuals affected by some degree of color blindness don’t see the world in black and white, but merely have an altered or decreased ability to perceive colors. The occurrence of color deficiencies — especially in males — might be greater than you realize: as many as eight percent of men with Northern European ancestry are afflicted by color deficiency. But despite the prevalence of this visual disability, most Americans share a very poor understanding of how color blindness works.


When light from any source reaches an object, some of that light is absorbed by the object while the rest is reflected. The reflected light reaches the light-sensitive retina at the back of your eye. Photoreceptors called “cones” respond to the incoming wavelengths of light, sending signals to your brain regarding how to interpret the perceived light through the optic nerve. Slightly less than two thirds of these cones respond most strongly to red light, while approximately one third react strongly to green light. Only about two percent respond strongly to blue light. Having three different types of cones, humans can perceive colors better than most mammals on Earth. But when humans don’t properly develop these retinal cones, a color deficiency arises.


Most color deficiencies involve a loss or limited function of the red-perceiving cones known as protans. This form of color blindness is commonly called red-green color blindness. A few different types of red-green color blindness exist:

  • Protanomaly: In individuals with protanomaly, the red cone photopigment suffers from an abnormality. Red, orange, and yellow appear greener to individuals with protanomaly, and colors do not appear as bright in general. This condition is fairly negligible, and doesn’t typically affect one’s normal daily life. Protanomaly is an X-linked disorder, affecting approximately one percent of males.
  • Protanopia: People with protanopia have no working red cones. To these individuals, red appears as black. Specific hues of orange, yellow, and green appear as yellow. Protanopia is also linked to the X chromosome, and affects approximately one percent of males.
  • Deuteranomaly: In those with deuteranomaly, there is an abnormality in the green cone photopigment. Yellow and green are redder, and affected individuals have a difficult time distinguishing between blue and violet. Deuteranomaly is the most common form of color deficiency, affecting 5 percent of males.
  • Deuteranopia: Individuals with deuteranopia lack working green cone photoreceptors. They tend to perceive shades of red as a yellow-brown mix, and greens as beige. Deuteranopia affects about 1 percent of males.


Other types of color blindness, such as blue-yellow color blindness and monochromacy, are exceptionally rare, and can have a major impact on an individual’s life. Color blindness can affect all humans, but is considerably more rare in females than in males since red-green color deficiencies are linked with the X chromosome.

If you suspect that you may have some form of color deficiency and would like to be tested, call Silverstein Eye Care Centers today at (816) 358-3600 or request an appointment online. Note that many people will live their entire lives without realizing they are colorblind!

Posted September 15, 2015 by Silverstein Eye Centers
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