What is color blindness?
Color blindness — also known as color vision deficiency (CVD) — is a condition where you don’t see colors in the traditional way. This can happen if certain cells known as photoreceptors, or more specifically cones, in your eyes are missing or not working correctly. These cones typically allow you to see each color on the rainbow. If you have color blindness, you might not see each of these colors.
Don’t confuse color blindness with a type of blindness (a condition where you have limited or no sight) — color blindness is simply a change in the way your eyes see color.
We all see a continuum (range) of colors, but which ones we see depends on how well our photoreceptors function. Photoreceptors are cells within your eyes that respond to specific wavelengths of light. Everyone sees color slightly differently, and the way we see colors may also change as we age if we develop certain age-related eye conditions such as cataracts.
Why do we see different colors?
When we see different colors, what we’re really perceiving is different wavelengths of light. Your eyes contain photoreceptors (cells) that process light entering the eye to help you perceive color. Rods detect differences between dark and light. Cone cells detect colors when lighting conditions are bright enough. Each wavelength corresponds to a different shade in the visible spectrum of light. Reds are the longest wavelengths, greens are medium and blues are the shortest.
What colors of the rainbow do people with color blindness see?
Generally, people with color blindness have difficulty articulating what they perceive, but scientists suggest the typical colorblind person might see colors as varying shades of blue and yellow. For example, what a color-normal person calls purple and what a colorblind person calls purple may not be the same color. Or, both people may look at the same color and call it different things.
A person's color vision falls into one of the following categories:
Full color vision/Trichromacy: If you were born with normal-functioning color pigments in all three cone types in your eyes, you’re a trichromat. You’d see six colors in your rainbow: red, orange, yellow, green, blue and violet.
Color vision deficiency/Dichromacy: If you were born with missing or malfunctioning (not working) cones of one of the three types in your eyes, you’re a dichromat or dichromatous. What colors you see depends upon which cones are missing or malfunctioning.
If you’re a dichromat, there are several specific types of color deficiency you might experience, including:
Red-Green Color Deficiency:
- Protanopia: In this case, your long-length red-responsive photoreceptors also aren’t functioning correctly, so you won’t see reds or greens properly. Colors that contain red will also look different to you. Your rainbow will consist mainly of what trichromats call blues and golds.
- Deuteranopia: This time your green-responsive photoreceptors aren’t functioning. If you’re a deuteranope, your rainbow also appears as a series of blues and golds.
- Protanomaly: In this type of color deficiency, you have some red-responsive cones, but they aren’t working correctly. Your rainbow appears muted. Red may appear as dark gray and every color that contains red may be less bright.
- Deuteranomaly: In this case, green-responsive cones don’t work as they should. It’s the most common form of color blindness. Your rainbow is most likely blues, yellows and generally muted colors.
Blue-Yellow Color Deficiency:
- Tritanopia: This is blue-yellow color blindness. It means you have no blue-responsive cone cells. Your rainbow may contain reds, light blues, pinks and lavender.
- Tritanomaly: This type of color blindness is when your blue-responsive cone cells work, but not as well as a full color-sighted person. Your rainbow has greener blues and there is little or no yellow.
Fully Color Blind/Monochromacy: If you’re a monochromat, you have a very limited or no ability to see color. Your vision might be a lot like watching a black and white television or an old black and white movie. Your rainbow would appear in varying shades of gray.
Monochromats come in two types:
- Blue cone monochromacy: In this type of monochromacy, you only have one cone type that contains working photoreceptor cells. When only one cone type works, it’s difficult to tell between certain colors, and mostly you see grays. Blue cone monochromats may also have poor vision in general, light sensitivity, nystagmus or shaking of the eyes, and near-sightedness. Blue cone monochromacy is rare.
- Rod monochromacy: In this condition your retinal rod photoreceptors work but all or most cones are absent or malfunctioning. It’s also called achromatopsia. You see everything in grayscale. Achromats are also likely to suffer from low vision, nystagmus and light sensitivity.
How common is color blindness?
Color blindness is uncommon, but it does run in families. This means that if other members of your family have experienced color blindness, you’re more likely to have it too. Color blindness can happen in both men and women, but it’s much more commonly seen in men. This is because color blindness is passed down through your genetic code.
Sometimes, color blindness can also show up later in life. In some cases, it may have been present at birth but not noticed until later. In other cases, injuries or diseases of the eye can cause malfunctions in the parts of the visual system that allow color vision, including not just the photoreceptors but also the nerves and some retinal layers.
How is color blindness inherited?
Red-green color blindness, the most common form by far, is a genetic mutation that is passed to children on the X chromosome. At conception, an egg carries an X chromosome and the sperm cell can carry either an X chromosome or a Y chromosome. If you have an XX chromosome pair, the resulting baby will be female. If you have an XY chromosome pair, the baby will be male. The gene responsible for color blindness is located on the X chromosome. In other words, red-green color blindness is an X-linked recessive condition. If a female inherits one normal color vision gene and one mutated gene, she won’t be red-green color blind, because it’s a recessive trait. If she inherits two mutated color vision genes, she’ll be color red-green blind.
Since boys have only one X chromosome, their chance of inheriting red-green color blindness is much greater. Boys always inherit their X chromosome from their mother. If mom has red-green color blindness, or if mom’s dad is red-green colorblind, her son will be too.
Symptoms and Causes
What causes color blindness?
Color blindness is caused by a change (mutation) to your genes. In most cases, you’re color blind from birth. When you’re color blind, it’s usually because your eyes don’t contain the normally functioning cones needed for full color vision.
What are the signs and symptoms of color blindness?
You might have a form of color blindness if you have trouble:
- Telling the difference between certain colors.
- Seeing the brightness of certain colors.
- Distinguishing the difference between certain shades.
The signs and symptoms of color blindness can vary depending on the type. If you have inherited your color blindness (hereditary color blindness), the signs are often barely noticeable because you’ve always seen colors the same way. You may not realize that there’s a different way to see colors. However, if you have acquired color blindness — meaning you have color blindness because of an injury or illness — you may notice the shift in how you see colors, although some diseases affecting color vision progress too slowly for changes to be noticeable.
Who’s at risk for color blindness?
For most people with color blindness, the condition is there from birth. It’s passed down through their family. However, you can also develop color blindness from an eye injury, illness or even certain medications.
You might be at a higher risk of color blindness if you:
- Are male.
- Are white.
- Have family members who are also color blind.
- Take medications that modify your vision.
- Have eye diseases, including age-related macular degeneration, glaucoma or cataracts.
- Have Alzheimer’s disease, diabetes or multiple sclerosis (MS).
Does color blindness cause other health problems?
Red-green color blindness, the most common form, does not lead to additional vision loss or total blindness. But because the cone cells of the retina are also used to see fine details, people who are color blind may have vision that is less sharp. The other more rare forms of color vision can accompany other vision problems that do need to be taken care of by an eye doctor — especially in children. Anyone who suspects color blindness should start by scheduling an eye exam.
If you or your child is color blind, talk to your eye care provider about assistive aids that can help with your vision. If you ever notice other vision issues that come on suddenly and seem to be getting worse, reach out to your provider right away.
Diagnosis and Tests
How will an eye care provider diagnose my color blindness?
If you suspect that you or your child may have trouble perceiving particular colors, your eye care provider will perform a thorough eye exam and then show you an eye chart to determine how you see certain colors.
The first test for color vision deficiency was developed by Japanese ophthalmologist Ishihara Shinobu for military use in 1918. Today, the Ishihara test is still the primary test used to determine if you have red-green or blue-yellow color deficiency. You or your child will be shown a set of Ishihara color plates. For example, to test for red-green color blindness each plate has a red or green number hidden within a set of dots. If you can’t see the figure, you have tested positive for red-green color deficiency. There’s also a set of Ishihara plates with blue or yellow figures hidden within a set of dots. If you can’t see the blue or yellow figure, you’ve tested positive for blue-yellow color blindness.
How old should my child be to be tested for color blindness?
A child can be successfully tested for color vision deficiency around age 4. At that age, he or she is developed enough to answer questions about what he or she sees. Many schools will perform color vision tests at an early age to determine if color-coded learning devices will be an issue. If so, alternative learning materials can be chosen.
Keep in mind though that children should be screened for other related vision issues such as nystagmus and low vision at a younger age.
Management and Treatment
If a provider diagnoses me or my child with color blindness, what can I do?
There are several things you can do if you or your child have color blindness. There are tools that can help you in your daily activities, including:
- Corrective lenses: Tinted contact lens and glasses are available that can help you or your child reduce some of the bright light that is commonly an issue for people who are color blind. They do not specifically color-correct for you, but they may help you see better by reducing brightness and glare. Recently, color-correcting glasses were developed, but they seem to only work for one type of color blindness.
- Color buddy: Many people with color blindness find it helpful to have a friend with full color vision help with certain tasks, such as going along on trips to the store to buy paint or clothing.
- Memory aids: Memory aids can be great workarounds for everyday tasks. For example, there is no reason why a person who has a color vision deficiency can’t drive. Certain memory aids help, such as memorizing that green always appears at the top of traffic lights.
- Visual aids: There are many devices, apps and other visual aids that will help you tell the difference between certain colors. Some phone apps will allow you to take a photo and then interpret colors on each section for you.
Outlook / Prognosis
Can color blindness affect my child’s career choice?
Your child will learn to follow other cues rather than color, such as brightness or location, when taking on everyday tasks. It’s true that certain professions could be too challenging or dangerous to pursue with color deficiency, such as a career as an electrician, fashion designer, pilot or graphic artist. But there are many careers to choose from where the lack of full color vision wouldn’t factor into their success.
Can an eye care provider cure my color blindness?
Currently, color blindness cannot be cured. If your color blindness is related to a medication, your provider may suggest that you try a different medication without the same side effects. If your color blindness is related to an injury or disease, your provider will typically treat the underlying causes. Treating the cause of your color blindness may help correct the condition.
If your color blindness is genetic, there are gene therapies in development that may hold promise for the future. In the meantime, ask your eye care provider which assistive aids might help you work around your or your child’s color blindness and adapt to everyday living.
A note from Cleveland Clinic
It’s important to remember that everyone sees life through a different lens. For many people with color blindness, the condition doesn’t negatively impact their lives. If you or a member of your family is experiencing color blindness, it can help to reach out to your eye doctor. There may be options you can try to improve any challenges you encounter in your daily life.
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