Green and Red Color Blindness

Colorblindness refers to the inability to see color. True colorblindness is rare as most people are able to see some degree of color. However, there are those who experience poor color vision, or the inability to distinguish between certain colors. Red-green is the most common form of color deficiency and, according to the Mayo Clinic, affects one in 12 males of Northern European descent. The condition can also affect females but is much less common, occurring in less than 1 percent.

How Poor Color Vision Works

• The eye is similar to a camera and the retina is like film. Color film has special chemicals that convert light to a color image. Sometimes the chemicals degrade, or wear away, and the resulting picture is distorted. The retina works the same way. The retina has cones that react to different colors. With poor red-green vision the red and green cones are missing, or there aren't enough, so the picture looks distorted.

Symptoms

• There are varying degrees of poor color vision. A person with a mild case may be able to see red and green but be unable to distinguish between different shades of each color. For example, hunter green may look identical to chartreuse. Someone with a more severe case may see not be able to see red or green at all, both appearing as shades of brown or gray. Parents may not realize that a child is color blind until he starts learning colors and has trouble identifying reds and greens, or has trouble differentiating between the two.

Testing and Diagnosis

• The most common test for poor red-green color vision uses multi-colored dot patterns. In people with normal vision, a green image on a field of red dots is visible. In people with poor red-green color vision, the patterns may appear faint or as nondescript blobs.

Causes

• Disease, injury and aging can all affect color vision but poor red-green color vision is most often hereditary. The gene is passed down on the X chromosome and is more common in males. This is because the mother only provides X chromosomes while the father provides either an X or Y--girls are XX and boys are XY. If the mother passes the gene to her son, the Y from the father will not cancel out the gene on the X chromosome. If she passes the gene to her daughter, unless the father has poor color vision himself, the X he provides will cancel out that gene. The daughter will become a carrier but will not have poor color vision.

Advantages and Disadvantages

• People with poor color vision lead healthy, productive lives but they may have trouble performing some tasks. They can't always identify some food items or tell when produce is ripe by sight alone. They or may have trouble with traffic lights---especially single lights that could be red or yellow. By law people with poor red-green vision cannot hold certain jobs in the transportation industry and may be precluded from joining the armed forces. There are no treatments for the condition but people may wear tinted lenses to sharpen their vision. The lenses do not allow them to see color, but they may help objects to stand out better.

  Interestingly, a study by the University of Calgary School of Anthropology revealed that animals with poor color vision may have one major advantage: they are better at seeing through camouphlage than animals with broad color vision.

Simulating Poor Color Vision

• The eye needs adequate light to translate color. In low-light situations, colors appear muted and may even look gray or brown. To get a feel for what it's like to have poor color vision, try looking at colored objects under moonlight or in a dark room.