Color Blindness: A Comprehensive Guide

If you discover that you do not see and experience colors as well as other people in your life, you may have an eye condition known as color blindness. The condition is often genetic, but you can acquire it later in life following an injury or disease. The X chromosome passes it down from generation to generation, making it much more prevalent to appear in boys than in girls. 

The condition affects about 4.5 percent of the world population, or more than 350 million people.

Your optometrist can test you for color blindness upon request. There is no cure for color blindness, but there are several treatment options available that can improve your quality of life.

What Is Color Blindness?

Color blindness is an eye condition that changes the way you see colors. It happens because of a lack of certain types of cone cells (the cells responsible for color vision) inside the eye. 

If you have it:

• You may not be able to see some colors easily.
• You may have a hard time distinguishing between certain colors.
• You may see no colors at all.

Types of Color Blindness

There are three types of color blindness: red-green color blindness, blue-yellow color blindness, and complete color blindness. 

Red-Green Color Blindness

Four subtypes of red-green color blindness exist. They are:

• Deuteranomaly (when your green-sensitive cones do not work as well as your red-sensitive ones). You cannot see green well. This is the most common type of color blindness.
• Deuteranopia (when you have no cones that can see green light). You cannot tell the difference between green and red. 
• Protanomaly (when your red-sensitive cones do not work as well as your green-sensitive ones). You cannot see red well.
• Protanopia (when you have no cones that can see red light). You cannot tell the difference between red and green.

Blue-Yellow Color Blindness

There are two types of blue-yellow color blindness: 

• Tritanomaly (when your blue-sensitive cones do not work well). You have difficulty telling the difference between blue and green or red and yellow. 
• Tritanopia (when you have no cones that can see blue light). You cannot tell the difference between blue and green, yellow and pink or red and purple. You also have difficulty seeing bright colors in general. 

Complete Color Blindness

Everyone sees color a little differently — even people who aren’t color blind.

National Eye Institute

Complete color blindness, or monochromacy, occurs when you cannot see colors at all. This is the least common type of color blindness. People with this condition see everything in various shades of gray. Some types of monochromacy also cause additional vision issues like light sensitivity and trouble focusing your vision. 

Who Is Commonly Affected?

Medical data shows that men are about 16 times more likely to be affected by color blindness than women. This is because of the way that color blindness is passed down genetically. Because color blindness is usually genetic, people with close relatives who are affected by it are also more likely to be color blind themselves.

Symptoms

The symptoms of color blindness all relate to how you perceive color. People who are color blind may find it difficult to:

• Distinguish between some colors. 
• See brighter versions of some colors. 
• Tell the difference between shades of the same color. 

If you were born with color blindness, you may not realize that you are not seeing the same colors that everyone else can see. Many people only begin to suspect they may be color blind when someone else points out one or more of these symptoms. 

Not all cases of color blindness are equally severe. If your case is mild, you may not notice it for a long time – possibly your entire life. 

Causes

Color blindness is caused by one of two factors:

• Genetics. If color blindness runs in your family, you are more likely to be color blind yourself. 
• Injury or disease. If your eyes or brain are damaged by injury or disease later in life, you may lose the ability to see certain colors. 

The Genetics of Color Blindness

Color blindness is usually an inherited condition, meaning that it is caused by a genetic mutation that can be passed from parent to child. Color blindness is much more common in men than women due to the specific genes involved in this condition. 

Among populations with Northern European ancestry, red-green color vision defects occurs in about 1 in 12 males and 1 in 200 females.

National Library of Medicine

Red-green color blindness is passed through the X chromosome, one of the two sex chromosomes in the human genome. A male child has one X chromosome and one Y chromosome, while a female child has two X chromosomes.

This additional X chromosome gives girls some protection against color blindness. If they have one X with the mutation for color blindness, they will only be a carrier for the condition. For girls to be affected by it themselves, both of their X chromosomes must carry the mutation for red-green color blindness. This is only possible if both parents carry the mutation. 

However, boys lack a backup X chromosome. If their single X has the mutation for red-green color blindness, they will be affected by the condition. This means they only need one affected or carrier parent to develop them condition. 

Blue-yellow color blindness and complete color blindness are passed by chromosomes on different genes that are not linked to sex. As a result, they are equally common in men and women. 

Who Is at Risk?

You may be at greater risk of color blindness if you are: 

• Male
• White
• Part of a family with many color-blind members

Certain health conditions also increase your risk of developing color blindness later in life. These include:

• Macular degeneration
• Glaucoma
• Diabetes
• Alzheimer’s disease
• Parkinson’s disease
• Leukemia
• Sickle cell anemia
• Alcoholism

Because many of these conditions develop over time, color blindness is slightly more common in older people. 

You may also develop color blindness if you are taking the drug hydroxychloroquine (Plaquenil) to treat malaria, rheumatoid arthritis, lupus, or other conditions.

Diagnosis

Color blindness experts say about 4.5 percent of the world population, or more than 350 million people experience color blindness. If you suspect that you may be color-blind, you can ask your eye doctor to test you for the condition. 

First, they will perform a basic eye exam to rule out any other possible conditions. Then, they will administer one of two color vision tests: the Ishihara test or the color arrangement test. 

• During the Ishihara test, you will be asked to look at plates that are printed with circles made up of colored dots. There is a number hidden in each circle than can only be seen if you are able to see certain colors. If you cannot tell your eye doctor what that number is, you are likely color blind.
• During the color arrangement test, you will be asked to arrange a set of same-colored objects in order from lightest to darkest. This test is most useful for determining the severity of your color blindness.

Treatment

Color blindness has no cure, but treatment options can make it easier to live with. Among them:

• Special glasses or contacts. Corrective eyewear can be made with tinted lenses to help compensate for color blindness. 
• Assistive technology. Computers and mobile devices usually include display options that adjust colors to make them easier for color blind people to see. There are also many mobile apps that can identify colors for you, both online and in the real world. 
• Accommodations at school or work. Certain tasks are much more difficult or even impossible for color blind people to accomplish. When these tasks come up, ask for accommodations such as alternate assignments or work sharing arrangements.

References

1. What Is Color Blindness? (December 2021). American Academy of Ophthalmology.

2. Color Blindness. (July 2019). National Eye Institute.

3. Types of Color Blindness. (June 2019). National Eye Institute.

4. Causes of Color Blindness. (June 2019). National Eye Institute.

5. Colour vision deficiency (colour blindness). (April 2019). National Health Service (NHS).

6. Colour Blindness. (August 2020). Alberta Health Services.

7. Is it true that colour blindness only affects boys? (2021). Montreal Children’s Hospital.

8. Color Blindness. (December 2020). Cleveland Clinic.

9. Color blindness. (June 2011). Nature Methods.

10. Color Blindness. (April 2020). American Association for Pediatric Ophthalmology & Strabismus.

11. Colorblind People Population! Statistics. (2021). Colorwill.