About Color Blindness

Most people see the world the same way. However, some people have a color vision deficiency, which means that how they see colors is different than what most of us see. In severe cases, people with color blindness aren't aware of the differences between colors, and they may not even realize that they don't see the world like everyone else does unless they have their color vision tested by a medical professional.

Causes of Color Blindness

Color blindness is usually a hereditary condition, meaning that you are born with it, but it can also be caused by aging, injury to the eye, glaucoma, or macular degeneration. This condition comes about due to a difference in eye structure. In the macula, a part of the eye connected to the retina, are three different types of cone cells, which allow us to see colors. When one of these types of cones doesn't work properly, color blindness results. If the problem is with the L-cones, also called protanopes, or M-cones, also known as deutanopes, the result will be red-green color blindness. Blue-yellow color blindness is caused by defective S-cones, or tritanopes.

• Facts About Color Blindness: Learn the basics about color blindness from the National Eye Institute.
• Causes of Color Blindness: Research about the specific causes of color blindness is still ongoing.
• What Causes Color Blindness? Color blindness is usually, but not always, inherited from your parents.
• Color Blindness: How do we perceive color, and how is this different for people who are color-blind? Learn more here.
• What Are the Symptoms and Causes of Color Blindness? Find out more about where color blindness comes from and how to spot it.
• Color Blindness: Read about this condition and what causes it on this page from the National Library of Medicine.

Different Types of Color Blindness

The most common types of color blindness involve red-green deficiencies, in which the person has a hard time telling the difference between these two colors. Protanopia is a red deficiency, which causes the person to see reds more like beiges and experience them as being darker than they are. Deuteranopia, a green deficiency, is the single most common type of color blindness, and people with this condition are insensitive to greens. The result is much like that of protanopia, but people with deuteranopia can often tell the difference between shades of red and green more accurately. The third color deficiency is tritanopia, blue deficiency. With this condition, blue and green look similar, and yellow can sometimes look like red. The rarest type of color blindness is achromacy, which is the experience of no color at all: Everything is in shades of gray.

• Types of Color Blindness: Defects in the three different types of cones can cause different types of color blindness.
• Color Blindness: How it Happens and What it Is: A thorough article on the types of color blindness and how they are caused.
• Color Deficiency: A person's ability to perceive colors can vary from person to person and even within one person, with one eye seeing colors better than the other.
• Blue Cone Monochromacy: This rare condition can cause symptoms including poor overall vision and intolerance to light.
• The Evolution of Trichromatic Color Vision: Explore the origins of color vision in our primate ancestors with this article.
• Theories of Color Vision: Two different schools of scientific thought have sprung up around the topic of color vision.

How Color Blindness Impacts Males and Females

Men are more likely to inherit color blindness than women. This is because color blindness is a recessive trait that is carried on the X chromosome. Since men only have one X chromosome, they only need one copy of this gene to be color-blind, but in women, who have two X chromosomes, two copies of the gene are necessary; otherwise, the dominant trait of having full color vision will be expressed. A woman with only one copy of the gene for color blindness is a carrier for this trait but does not experience it herself. However, she has a 50% chance of passing on this gene to her children; if she passes this gene on to her daughter, and if the child's father is color-blind, the girl will be color-blind as well.

• Color Blindness or Color Vision Deficiency: Test your perception of color and learn more about these conditions with the information on this page.
• Accommodating Color Blindness: Learning more about this condition can help people designing websites to accommodate all users.
• What it's Like to Be Color-Blind: Watch this video to learn more about how color-blind people experience the world.
• Color Blindness, Partial, Deutan Series: Explore the science behind color blindness with this journal article.
• Understanding Genetics and Color Blindness: A bit of knowledge about dominant and recessive traits and how chromosomes work can shed light on the heritability of this condition.