Overview

Color blindness (color vision deficiency) is a fairly common condition in which you don’t see colors in the traditional way. This happens when cones (a type of nerve cell in your eye retina) aren’t working correctly. Cones process light and images as they enter your eye and send signals to your brain that allow you to perceive color.

Color blindness usually doesn’t mean you can’t see any colors. The vast majority of people with color blindness see a range of colors, but they see some colors differently than others do. They may also have trouble telling the difference between certain colors or shades. Some very rare forms of color blindness make a person unable to see any colors.

For most people, color blindness is inherited. That means it’s passed down from your biological parents — from the mother or birthing parent in the most common red-green forms of color blindness. But you can also acquire color vision deficiency later in life due to medical conditions or other reasons.

If you or your child has color blindness, it’s important to learn the type and severity. Talk to an eye care provider (optometrist or ophthalmologist) about the nature of the condition and how it may affect you.

Types of color blindness and what people can see

There are several types of color blindness, defined according to which types of cones aren’t working well. To understand the types of color blindness, it helps to know a bit about cones.

Cones are nerve cells in your eye that detect colors in the visible spectrum of light. This spectrum includes all the wavelengths that humans can see. These range in length from 380 nanometers (short), or nm, to 700 nanometers (long). Normally, you’re born with three types of cones:

  • Red-sensing cones (L cones): These cones perceive long wavelengths (around 560 nanometers).
  • Green-sensing cones (M cones): These cones perceive middle wavelengths (around 530 nanometers).
  • Blue-sensing cones (S cones): These cones perceive short wavelengths (around 420 nanometers).

Most people have all three types of cones, and these work as they should. However, if you have color vision deficiency, at least one type of cone isn’t working properly. Problems with your cones affect your ability to see colors in the traditional way. General categories that describe how many types of cones you have, and how well they’re working, include:

  • Trichromacy: All three types of cones are present and working properly. You see all colors on the visible spectrum of light in the traditional way. This is full-color vision.
  • Anomalous trichromacy: You have all three types of cones, but one type isn’t as sensitive to light in its wavelength as it should be. As a result, you don’t see colors in the traditional way, with variations from normal ranging from mild to severe. In mild cases, you may just confuse pale or muted colors. In more severe cases, you may also confuse vivid and pure (fully saturated) colors. These types of color blindness have names that end in “anomaly” (which indicates partial vision of a specific color).
  • Dichromacy: One type of cone is missing. So, you only have two types of cones (usually S cones along with either L cones or M cones). You see the world through the wavelengths that those two types of cones can perceive. It’s hard to tell the difference between fully saturated colors. These types of color blindness have names that end in “anopia” (which indicates absence of vision of a specific color).
  • Monochromacy: You only have one type of cone, or you have no cone function at all. You have very limited or no ability to see color. Instead, you see the world in varying shades of gray.

Within these general categories, there are many specific types of color blindness.

Red-green color deficiency

Red-green color deficiency is the most common type of color blindness. It affects how you see any colors or shades that have some red or green in them. There are four main subtypes:

  • Protanopia: Your L cones are missing. So, you can’t perceive red light. You mostly see colors as shades of blue or gold. You may easily confuse different shades of red with black. You may also confuse dark brown with dark shades of other colors, including green, red or orange.
  • Deuteranopia: Your M cones are missing. So, you can’t perceive green light. You mostly see blues and golds. You may confuse some shades of red with some shades of green. You may also confuse yellows with bright shades of green.
  • Protanomaly: You have all three cone types, but your L cones are less sensitive to red light than they should be. Red may appear as dark gray, and every color that contains red may be less bright.
  • Deuteranomaly: You have all three cone types, but your M cones are less sensitive to green light than they should be. You see mostly blues, yellows and generally muted colors.

Protanopia and deuteranopia are examples of dichromacy. Protanomaly and deuteranomaly are examples of anomalous trichromacy.

Other terms you might hear are “protan” and “deutan.” Protan and deutan are shorthand ways to talk about red-green colorblindness. Deutan refers to green (you have impaired or missing green-sensing cones, or M cones). Protan refers to red (you have impaired or missing red-sensing cones, or L cones).

Red-green color blindness is much more common among men and people assigned male at birth (AMAB) compared to women and people assigned female at birth (AFAB). This is because the genes for the color vision cone light-sensitive proteins are on the X chromosome, of which males have one and females have two. So if the one X in a male contains abnormal genes, the color blindness will reveal itself, while females can compensate with the other normal gene on the second X chromosome.

Blue-yellow color deficiency

Blue-yellow color vision defects (tritan defects) are much less common and include:

  • Tritanopia: You have no S cones. So, you can’t perceive blue light. You see mostly reds, light blues, pinks and lavender.
  • Tritanomaly: You have all three cone types, but your S cones are less sensitive to blue light than they should be. Blues look green, and you see little or no yellow.

Blue-yellow color blindness equally affects people AMAB and people AFAB.

Blue cone monochromacy

This is the rarest form of color blindness. With this type, you don’t have working L cones or M cones. You only have S cones. It’s hard to tell the difference between colors, and you see mostly grays. You may also have other eye problems, including sensitivity to light (photophobia), nystagmus and nearsightedness.

Rod monochromacy (achromatopsia)

Achromatopsia is when all or most of your cones are missing or don’t work properly. You see everything in shades of gray. You also have other vision issues that may greatly impact your quality of life.

Who does color blindness affect?

Inherited color blindness mostly affects men and people assigned male at birth (AMAB). This is due to its genetic inheritance pattern (X-linked recessive). Conditions passed down in this manner are much more common among people AMAB.

People can also acquire color blindness due to certain medical conditions, medications or environmental exposures.

How common is color blindness?

Among people of Northern European ancestry, red-green color blindness affects about 1 in 12 people AMAB and 1 in 200 people AFAB. These numbers vary by ethnicity. Some research shows that Europeans have the highest prevalence of color blindness.

Here are some statistics about the less common forms of color blindness:

  • Blue-yellow color deficiency affects 1 in 10,000 people.
  • Achromatopsia affects 1 in 30,000 people.
  • Blue cone monochromacy affects 1 in 100,000 people.

Overall, around 300 million people around the world have some form of color blindness (mostly red-green).

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Complications

Blood clots are a dangerous complication of atrial fibrillation (AFib). Blood clots can lead to stroke.
The risk of stroke from AFib increases as you grow older. Other health conditions also may increase the risk of a stroke due to AFib. These conditions include:
  • High blood pressure.
  • Diabetes.
  • Heart failure.
  • Some types of heart valve disease.
Blood thinners are commonly prescribed to prevent blood clots and strokes in people with atrial fibrillation.

Prevention

Healthy lifestyle choices can reduce the risk of heart disease and may prevent atrial fibrillation (AFib). Here are some basic heart-healthy tips:
  • Control high blood pressure, high cholesterol and diabetes.
  • Don't smoke or use tobacco.
  • Eat a diet that's low in salt and saturated fat.
  • Exercise at least 30 minutes a day on most days of the week unless your health care team says not to.
  • Get good sleep. Adults should aim for 7 to 9 hours daily.
  • Maintain a healthy weight.
  • Reduce and manage stress.


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