Color Blindness

What is color blindness?

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 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 males. 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 males and females.

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 males. This is due to its genetic inheritance pattern (X-linked recessive). Conditions passed down in this manner are much more common among males.

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 males and 1 in 200 females. 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).

What causes color blindness?

Color blindness can be either inherited (you’re born with it) or acquired (you develop it later in life). The causes are different in each case.

Causes of inherited color blindness

A change (mutation) to your genes causes inherited color blindness.

The most common form, red-green color blindness, follows an X-linked recessive inheritance pattern. Conditions inherited in this way usually affect male babies and are rare among female babies. Here’s a breakdown of the genetics for red-green color blindness.

A male baby:

• Will inherit red-green color blindness if the mother has the condition.
• Has a 50% chance of inheriting red-green color blindness if the mother is a carrier (this means the mother carries one copy of the genetic mutation but doesn’t have the condition). The other copy is normal, hence the 50:50 chance.
• Won’t inherit the condition if only the father has it because the father contributes the Y chromosome to male babies and the X chromosome to female babies.

A female baby:

• Will inherit red-green color blindness if both parents have the condition.
• Will be a carrier if the father has the condition but the mother doesn’t (and isn’t a carrier).
• Will either inherit red-green color blindness (50% chance) or be a carrier (50% chance) if the father has the condition and the mother is a carrier.

Causes of acquired color blindness

Acquired color blindness, which usually develops as blue-yellow color deficiency, has many possible causes. These include:

• Exposure to chemicals that harm your nervous system, such as organic solvents, solvent mixtures and heavy metals.
• Long-term exposure to welding lights.
• Medications, including hydroxychloroquine (to treat rheumatoid arthritis).
• Eye conditions, including age-related macular degeneration, glaucoma and cataracts.
• Medical conditions that affect your brain or nervous system, including diabetes, Alzheimer’s disease and multiple sclerosis (MS).

Acquired color blindness is less common than inherited forms.

What are the symptoms of color blindness?

You might have a form of color blindness if you have trouble:

• Telling the difference between certain colors or shades.
• Seeing the brightness of certain colors.

But to recognize these symptoms, you need to know to look for them. Many people with color blindness don’t know to look for these differences because they’ve always seen colors in the same way. So, they don’t realize anything’s different about their color vision.

That’s why it’s important for children to have a comprehensive eye exam that includes colorblind testing before starting school. Many tests and other classroom materials rely on color to convey information or measure students’ learning. Children who see colors differently may struggle with these materials.

How is color blindness diagnosed?

Eye care providers diagnose color blindness using several different tests.

The Ishihara test is the most common test eye care providers use to diagnose red-green color blindness. For this test, a provider shows you a series of color plates. Each plate contains a pattern of small dots. Among those dots, there’s a number (or shape for young children). You identify what you can see on each plate. Some plates include numbers that you can only see with full-color vision. Others include numbers that you can only see with color vision deficiency.

Based on the results of the Ishihara test, your provider may recommend further testing to confirm a diagnosis and learn more.

If you believe you or your child may have color blindness, contact an eye care provider to schedule an eye exam. Be sure to mention your concerns at your appointment.

How old should my child be for colorblind testing?

Color vision deficiency testing is generally appropriate for children ages 4 and older. By age 4, most children can answer questions about what they see. However, your child should have their first comprehensive eye exam much sooner (before their 1st birthday).

What is the treatment for color blindness?

Currently, there’s no medical treatment or cure for people with inherited color blindness. If you have acquired color blindness, your healthcare provider will treat the underlying condition or adjust your medications as needed. This may help improve your color vision.

You may have heard of color-blindness glasses. Such glasses may provide a richer color experience for people with mild forms of anomalous trichromacy. The glasses enhance the contrast between colors so people with color vision deficiency can see the differences more clearly. But they don’t allow you to see any new colors, and the results vary based on the individual. Plus, it’s important to know that these glasses aren’t a cure and won’t correct any issues with your cones.

If you’re considering color-blindness glasses, talk to an eye care provider first to learn if they’ll make a difference.

What can I expect if I have color blindness?

Color blindness might not affect your life much, especially if your condition is mild. More severe forms may interfere with your job, education or personal life. It’s important to talk to your eye care provider about your condition and what you can expect going forward. If your child has color blindness, ask what you can do to help them with school.

Can color blindness affect my child’s career choice?

Certain careers may be too challenging or unsafe to pursue with color deficiency. These include careers as an electrician, pilot, fashion designer or graphic artist. But you can encourage your child to pursue other careers where color vision won’t play a major role. Talk to counselors or mentors at your child’s school to access resources on career options.

How can I reduce my risk of color blindness?

You can’t prevent inherited color blindness. However, you may be able to lower your risk of acquired color blindness. Visit a healthcare provider for yearly checkups and ask about your risk for developing color vision deficiency. Some questions to ask include:

• Do any of my medical conditions put me at risk for color blindness?
• Can any of my medications cause color blindness?
• Should I be concerned about any chemical or environmental exposures at my job?
• What can I do to lower my risk?

How do I take care of myself or my child?

Connect with others who have color vision deficiency or parents of children with the condition. They can share advice and resources for living with color vision deficiency from day to day. Some tips include:

• Find a color buddy who can help with shopping for items like clothes or paint.
• Memorize the correct order of colors on things like traffic lights.
• Download apps that help you identify colors in the world around you.

When should I see my healthcare provider?

For your eye health and overall health, it’s important to:

• Visit a primary care physician once a year.
• Visit an eye care provider (optometrist or ophthalmologist) once a year.

Your providers will tell you if you need to come in more often for follow-up appointments or additional testing.