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What is Color Blindness?

Updated on April 27, 2013

What is Color Blindness?

What disease affects 8% of men and 0.5% of women? That's right, color deficiency is one of the most common genetic diseases in the world. With numbers that high someone you know probably has some kind of color deficiency. Rods and cones allow you to see and tell colors apart. 99% of "color blind" people are just color deficient, which means one of the three cones doesn't function properly. The other 1% of people, the people who are truly color blind, cannot see any color, only black whites, and shades of grays. Genetic color blindness is a disease affects a lot of people and cannot be cured.


Red-green color blindness are most of the cases that involve a defective X-chromosome. Humans have 23 different pairs of chromosomes. One pair consists of two X-chromosomes on women and one X-chromosome with one Y-chromosome on men. Color vision in the red-green area is coded on the X-chromosome which is called a sex linked trait.This means if a man is a carrier of a defective X-chromosome he will have color blindness. On women the chromosome that is normal is in charge and so she is not colorblind but just a carrier for color blindness. Because a women needs two defective X-chromosome to be affected, this symptom is called X-linked recessive. So basically, if you are male and your father has a red-green color vision deficiency you can not inherit it from him. This means only women can be carriers for color blindness who pass it on to their sons, as shown in the picture.



Doctors usually can't identify color blindness from the chromosomes, usually they see symptoms around ages 3 to 5. It is very important to notice symptoms and get a diagnosis early because it could impact how they learn for the rest for the rest of their life.

Some symptoms are being able to see some colors, but not all of them. For example, you may not be able to tell the difference between red and green but can see blue and yellow. Sometimes children don't realize they're they are color deficient because they may see many colors and just not a few. They just think they just see like everyone else. People that have color deficiency are only be able to see a few shades of color, while most people can see hundreds of shades of colors. In rare cases, you may see only black, white, and gray. That is only 1% of people and are the only real color blind people. The others are just color deficient.

The rods and cones are affected in color blindness so most of the time you aren't able to do well in different shades of light because the cones allow you to distinguish color while the rods deal with darks and lights. For example some people can see fine in a brightly lit room but then they go into a movie theater and cannot see any color. The three types of color vision deficiency are: protan, deutan, and tritan defects. Protan is where you mainly can't see reds and greens. Deutan is the most common type and is very similar to protan except the greens are a lot worse. People affected by tritan color blindness confuse blue with green and yellow with violet.

Usually people know that they are color blind from a young age, but sometimes it isn't inherited. You can become color blind from aging, eye problems, such as glaucoma, macular degeneration, cataracts, diabetic retinopathy, injury to the eye, and side effects of some medicines. These types of people usually know when they have had changes to their vision because they can tell the difference, but people that inherit it have had it all of their lives. That is why children should be tested early on because they could have color blindness and not know until they're in school and have trouble reading and learning.


Doctors can diagnose this genetic disease from a couple of different tests. The first test is the most common and you usually see it in health books. It is the test where you look at a circle of colored dots and try to see a pattern, letters, or numbers. This test is called the Ishihara test and there is a picture of it to the right.

Another type of test is where the doctor gives you a set of colored chips and you have to organize them by what color they are. They do this because people who have normal vision can see hundreds of different shades while people with this genetic disease only can see about twenty.

The most accurate test is a anomaloscope. This is a test where you have two different colors that you must change to be the same color by adjusting the brightness of one of them.

Color blindness can affect how young children learn so it is very important for it to be detected early so they can learn how to overcome it. They will have it for the rest of their life so it's better to start early.


Inherited color blindness can never be fully treated or corrected. The technology is not available yet. They do have special glasses, and colored contacts that can help though. Also glasses the reduce glare can greatly help. When people where these special contacts they actually aren't both the same. The picture on the next page shows how glasses can greatly help, but it is still not as good as a persons vision without color blindness.


Color deficiency affects so many people in the world, sadly there is no cure and people just have to live without seeing certain colors or anyl colors at all. Many people that are color blind feel handicapped doing everyday things, but almost no one realizes this. All of these things make me so thankful for being able to see color.


Healthwise Incorporated,, Color Blindness Topic Overview

American Academy of Ophthalmology,, What Is Color Blindness?

Daniel Flück,, 50 Facts about Color Blindness

Optical Diagnostics,, About color vision defects


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