Some individuals have a color vision deficiency, meaning their perception of colors is different from what many of us see. The most intense forms of these deficiencies are referred to as color blindness. People with color blindness are not aware of differences with colors that are obvious to the rest of us. People who do not have the more severe types of color blindness might not even be aware of their condition unless they are tested in a laboratory or clinic.
Color blindness that came from inheritance is caused by abnormal photopigments. These color-detecting molecules are found in cone cells. These are cone-shaped cells within the retina. Several genes are needed for the body to make photopigments and defects in these genes could lead to color blindness.
Sometimes color blindness could be caused by chemical or physical damage to the optic nerve, eye or parts of the brain that process color information. Color vision can also decrease with age because of cataracts. This is a clouding and yellowing of the lens of the eye.
Who will most likely get color blindness?
As many as eight percent of males and a half percent of females with Northern European ancestry have the common form of red-green color blindness.
Males are much more likely to be colorblind than females because the genes responsible for the inherited color blindness are on the X chromosome. Men only have one X chromosome and women have two X chromosomes. A functional gene on only one of the X chromosomes is enough to compensate for the loss on the other in women. This inheritance pattern is called X-linked, which primarily affects males. Inherited color blindness can happen at birth, start in childhood or not appear until the adult years of one’s life.
Are there different types of color blindness?
The most common types of color blindness are usually inherited. They are the result of defects in the genes that have the instructions for making the photopigments found in cones.
Red-Green Color Blindness
Hereditary color blindness is due to the limited function or loss of red cone, known as protan, or green cone, known as deutran photopigments. This kind of color blindness is mostly referred to as red-green color blindness.
Males with protanomaly have an abnormal red cone photopigment. Yellow, red and orange appear greener and colors are not as bright. This condition is mild and does not usually interfere with daily living. Protanomaly is an X-linked disorder estimated to affect one percent of males.
There are no working red cone cells in males with protanopia. The color red looks black. Certain shades of yellow, orange and green all appear as yellow. Protanopia is an X-linked disorder that is estimated to affect one percent of males.
The green cone photopigment is abnormal in men with deuteranomaly. Green and yellow appear redder and it is hard to tell violet from blue. This condition is mild and does not interfere with day to day activities. Deuteranomaly affects five percent of men.
There are no working green cone cells in males with deuteranopia. They tend to see the color green as beige and red as brownish-yellow. Deuteranopia is an X-linked disorder that affects about one percent of males.
People with tritanomaly have functionally-limited blue cone cells. Blue appears greener and it could be hard to tell red and yellow from pink. Tritanomaly is very rare. It is an autosomal dominant disorder affecting both women and men equally.
People with tritanopia have a lack of blue cone cells. The color blue looks green and yellow looks violet. Tritanopia is a very rare autosomal recessive disorder that equally affects both men and women.
Individuals with complete color blindness, or monochromacy, do not experience color at all. Clearness of their vision might also be affected.
If you think you are experiencing color-blindness, click here to see ophthalmology and adult strabismus expert Dr. Sami for an exam!