What to Know About the Different Types of Color Blindness

Color blindness, or color vision deficiency, refers to the inability of a person to correctly distinguish certain colors. Many people mistakenly believe that to be color blind is to view the world in only black and white, but complete color blindness is rare. A color-blind person usually has problems distinguishing certain colors, mistaking them for the same color.

In our eyes, there are cells known as cones that help us differentiate colors. There are three different types of cones—one allowing us to see red, one allowing us to see green, and another allowing us to see blue. When one has color blindness, one or multiple cone types are either absent or not functioning properly, resulting in them not seeing certain colors or seeing colors differently.

Types of Color Blindness

About 8% of men and 0.4% of women are color vision deficient. There are different types of color blindness, with some being more common than others.

Red-Green Color Blindness

A color-blind person usually has problems distinguishing between the colors red and green, mistaking them for the same color. This type of color blindness is the most common. The different types of red-green color blindness are:

  • Dueteranomaly is the most common type, in which green appears more like red.
  • Protanomaly is the opposite of deuteranomaly, in which red appears more like green and less bright.
  • Protanopia is when one is unable to see red.
  • Deuteranopia is when one is unable to see green.

Yellow-Blue Color Blindness

While red-green color blindness makes it hard to distinguish between red and green, yellow-blue color blindness makes it hard to tell the difference between blue and green and between yellow and red. Occurring in fewer than one in 10,000 people worldwide, this type of color blindness is less common and affects males and females equally.

There are two types of yellow-blue color blindness:

  • Tritanomaly: With tritanomaly, you cannot differentiate between blue and green and between yellow and red.
  • Tritanopia: If you have tritanopia, you're unable to differentiate between blue and green, purple and red, and yellow and pink. Colors also appear less bright to you.

Complete Color Blindness

A person with complete color blindness or complete achromatopsia has no functional cones and cannot see any colors. Sometimes, a person may have incomplete achromatopsia in which there are some functional cones, only allowing them to see certain colors. Those with achromatopsia commonly have impaired vision, light sensitivity, and nystagmus.

Achromatopsia in general is rare and is estimated to affect one in 30,000 people worldwide, with complete achromatopsia being more common than incomplete achromatopsia.

Figure comparing different types of color blindness
The different types of color blindness.

Melillo P, Riccio D, Di Perna L, et al. / IEEE J Transl Eng Health Med

Causes

Color blindness is caused by cells in the retina that incorrectly process colors. Specialized cone cells, which are responsible for color vision, lack the ability to send the correct signals to the brain.

Color blindness is usually hereditary, meaning that the condition is typically passed down from parents. Occasionally, certain diseases can affect the eyes or the brain and cause color blindness, referred to as "acquired color blindness." Some of these diseases include:

Some medications, notably Plaquenil (hydroxychloroquine), can affect the cells in the eyes and sometimes cause color blindness. Aging can also cause the disorder; as the lens darkens with age, older people may find it difficult to distinguish colors.

Symptoms

The main symptom of color blindness is difficulty distinguishing between red and green or blue and yellow. Parents will often suspect color blindness when their child has difficulty learning colors. Children having problems at school should be tested for color blindness, as many learning materials rely heavily on students being able to differentiate between colors.

Diagnosis

The most common test for diagnosing color blindness is the Ishihara test. This quick and simple test consists of a series of pictures made up of colored dots. Among the dots is a figure, usually, a number made up of dots of a different color. A person with normal color vision will be able to see the number, but a color-blind person will see a different number or no number at all.

A picture displaying an Ishihara test for color blindness
The Ishihara test.

American Optometric Association

Another test used to diagnose color blindness is called an arrangement or hue test, in which the patient is asked to arrange a group of colored chips or blocks in a particular order.

Treatment

Unfortunately, there is no cure for color blindness. However, people with color vision deficiencies learn ways to cope with the disorder. Patients usually teach themselves how to differentiate between different colors and shades of colors.

Some doctors prescribe color-corrective lenses, depending on the severity of the color vision deficiency. Additionally, there are computer software and phone applications that help those with color vision disorders.

Adjusting

If you have color blindness, there are many strategies that can help you accomplish everyday tasks and recognize colors easily. First, you can talk to your doctor about contact lenses or glasses designed for those with color blindness. Such contacts and glasses may help differentiate between colors you have difficulty seeing.

There are also smartphone apps that use your phone's camera to name colors, which can be helpful when shopping for clothes or other items and knowing the colors of your surroundings.

You can also ask those around you about colors you have difficulty seeing, especially the staff of the store you're visiting.

In the United States, it's legal to drive if you're color blind. Traffic light colors are strategically ordered to help drivers know which light is displaying. For vertical lights, the red light (stop) is always at the top, the green light (go) is always on the bottom, and the yellow light (slow down) is always in the middle.

For horizontal lights, the red light (stop) is always on the left side, the green light (go) is always on the right side, and the yellow light (slow down) is always in the middle.

A Word From Verywell

Color blindness is a rare condition that causes very few limitations for those affected. By knowing strategies like memorizing traffic lights and utilizing implements like color-corrective lenses, those with color blindness are often able to adjust and live normal lives.

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