- Color blindness is a common condition that causes problems seeing the difference between certain colors
- Most people who are color blind actually have a color vision deficiency, as true color blindness is rare
- There are different types of color vision deficiencies based on the light wavelengths your eyes can detect
- An eye doctor can diagnose color blindness with color vision tests
- Color vision tests are also available online, though most only screen for red-green deficiency
- There’s no cure for color blindness, but specialized lenses can help
What is Color Blindness?
Color blindness causes you to see colors differently than most people. This common condition makes it difficult to distinguish between certain colors.
Many people use the term “color blind.” However, it’s rare for anyone to be truly blind to all colors, as that’s a very severe form of the condition. More accurate terms to describe most people’s experience might be “color vision deficiency” or “poor color vision.”
Color Vision Testing
Typically, eye doctors screen people for color blindness and vision deficiency at routine appointments. However, it’s possible to test yourself online under certain circumstances.
If you take the Color Blind Test or the EnChroma Test online, for example, they both list a set of instructions before proceeding further. One of those instructions is to adjust your screen to 100% brightness, as this prevents false positives. Brightness makes colors easier to perceive.
Both tests employ the “Ishihara” method, which places digits inside circles and asks test takers to identify the hidden digit. It’s important to remember that this type of test only screens for red-green color blindness.
There are a number of different types of color vision tests out there, but Ishihara is the standard screening method.
The most common type of color vision test that eye doctors use is the Ishihara test. It uses pseudoisochromatic color plates to test for red-green color deficiency.
Inside each color plate is a number (or a symbol) consisting of dots in a particular color. Typically, there is a number on each test plate, although the dot arrangements can also be other patterns.
Your eye doctor, or online test, will ask you to identify what you see on each plate. People who are color blind may not be able to see any number or pattern on a given plate.
Hardy, Rand, and Rittler Test
Another test that uses pseudoisochromatic color plates is the Hardy, Rand, and Rittler (HRR) test.
This test looks very similar to the Ishihara test. The most significant difference is that the Ishihara test only screens for red-green deficiencies, while the HRR test can also screen for blue-yellow color vision problems.
The tests mentioned above are only screening tools. They don’t pick up on subtle color vision deficiencies.
If your eye doctor suspects a color vision problem, they may administer arrangement tests. These have a greater level of sophistication.
Farnsworth-Munsell 100-hue Test
The Farnsworth-Munsell 100-hue test, for example, provides more details than pseudoisochromatic color tests. The Farnsworth D-15 test is a shortened version of this test.
Both tests require the patient to arrange several colored discs in a particular order. The order depends on the color and intensity of the color. Based on the mistakes you make in the arrangement, your eye doctor can determine any color vision deficiencies.
Farnsworth Lantern Test
The Farnsworth Lantern test involves showing people nine pairs of vertically-aligned dots of light. They can be green, yellow, or red. Some pairs may be the same color.
The pairs appear for two seconds, and the test taker identifies the colors in each pair.
This test determines a person’s ability to identify maritime and aviation signal lights. It screens for moderate and severe cases of color deficiency but does not rule out mild conditions.
What Causes Color Blindness?
People can inherit or acquire color blindness. They inherit the condition when it passes through genes and is present at birth. Acquiring the condition means that color blindness occurs later in life, usually due to damage or disease.
People can acquire color blindness in many ways, including:
- Age-related changes
- Eye diseases and injuries
- Certain medications
- Chemical toxicity
Frequency of Color Blindness in the Population
About eight percent of men are born with a color vision deficiency. It's less common in women, affecting only about half a percent.
Almost all colorblind people have red-green color blindness, while very few have blue-yellow or full-color blindness (monochromacy).
Types of Color Blindness
Different forms of color blindness cause problems seeing particular colors.
Red-Green Color Blindness
Red-green color blindness is the most common type. This condition is genetic but can also develop due to eye disease. It occurs when a person has an impairment in a red cone or green cone pigment perception.
People who are red-green color blind tend to confuse purple, blue, green, orange, and red.
Most colorblind people with this red-green deficiency inherit it from their mothers. Boys are more likely to inherit red-green color blindness because their mother alone can pass it on.
For a girl to have this type, she must inherit the trait from her mother and have a father who's red-green color blind.
You can also develop red-green color deficiencies from eye diseases that damage your retina or optic nerve.
There are three types of red-green color blindness:
Most people who are red-green color blind have this type. An atypical green cone pigment causes the condition, which makes green and yellow appear red.
Colorblind people with this variation may also have difficulty perceiving purple and blue. This common form of color blindness is mild and usually doesn’t interfere with everyday tasks.
This type results from an abnormality in red cone pigments. It makes the red, orange, and yellow look more greenish and less vivid.
Like deuteranomaly, it’s mild and typically doesn’t interfere with daily activities.
3. Protanopia and Deuteranopia
These two types are similar because they result in an inability to distinguish between red and green. Experts usually group them into one category. However, they have different causes.
Protanopia is the result of red cone pigments that are missing. This means that red appears black, and certain shades of orange and green appear yellow.
Deuteranopia occurs when a person has missing green cone pigments. As a result, they see green as dark yellow and red as yellow-brown.
Blue-Yellow Color Blindness
People with blue-yellow color blindness have non-existent or poorly functional blue cone cells. They have difficulty distinguishing between yellow and red and between blue and green.
This type of color blindness is rare. It occurs in about one out of every 10,000 people and affects men and women equally.
Most people with blue-yellow color blindness develop it as the result of an eye condition, such as:
- Optic neuritis
- Diabetic retinopathy
- Age-related macular degeneration
- Central serous retinopathy
- Optic nerve damage
The two types of blue-yellow color blindness are:
People who are color blind in this way have an impairment in blue cone pigment function. Blue shows up as green, and there’s difficulty differentiating between pink, orange, yellow, and red.
People who have tritanopia don’t have blue cones. They can’t tell the difference between these colors:
- Blue and green
- Purple and red
- Pink and yellow
It also makes colors less bright.
Full-Color Blindness (Monochromacy)
People with monochromacy (or achromatopsia) have the most severe color vision deficiencies. They don’t see color at all. They see everything in shades of gray, black, and white.
This condition happens because two or all three types of cone photopigments are absent. It’s an extremely rare form of color blindness.
People who are color blind in this way will often wear dark glasses to help protect their eyes.
Eye Anatomy and Color Vision Deficiency
Color blindness occurs when your eyes don’t respond to certain wavelengths of light. Our eyes contain photoreceptors called rods and cones.
Rods are the cells that sense light and dark. Cone cells are sensitive to the different wavelengths of light and are responsible for color perception.
Rods and cones are divided into three types:
- Red light (long wavelength)
- Greenlight (medium wavelength)
- Blue light (short wavelength)
A person with normal color vision has trichromacy. This means they have a normal amount of the three cone types, all operating at full capacity.
Someone who is color blind or lives with color vision deficiency has one or more types of cones either missing or not fully functional.
Types of Color Vision Deficiency
Experts categorize red-green, blue-yellow, and full-color blindness into three categories. Each category has a different level of cone deficiency.
This condition is extremely rare, affecting one out of 100,000 people. It occurs when two or three sets of cones are missing.
As a result, people with monochromacy see all colors as black, white, and shades of gray.
- Cone monochromacy. Two of the cones are not functional
- Rod monochromacy. All three cones are not functional
People with dichromacy (dichromats) have only two types of cone cells that perceive color. The third type of cone pigment is absent, making it hard to see some colors.
An example is tritanopia, a type of blue-yellow color vision deficiency resulting from a lack of blue cones. Dichromats may be able to perceive color in bright and normal-light situations. However, their vision will deteriorate in poor lighting.
Experts consider anomalous trichromacy a form of color blindness to some extent. It typically isn’t as bad as other kinds of color vision complications. However, symptoms can range from mild to severe.
All three cone types are present to perceive light colors, but one of them is slightly off. The color perception difficulties depend on which cone is faulty.
Recent research shows that anomalous trichromats perform 14 percent worse, on average, in distinguishing colors compared to people with normal color vision.
What Do Color Blind People See?
Someone who is color blind has trouble seeing the difference between a red and a green object. In some cases, they also have difficulty seeing blues or yellows.
Additionally, the faultiness of certain cones may cause colorblind people to have difficulty distinguishing between other colors.
There are color blindness simulators online, such as the Coblis Color Blindness Simulator, which allows people to see what colorblind people see. Website developers can use these tools to test and optimize their content for colorblind viewers.
Thanks to modern technology, color blindness simulators are even available for browsers like Firefox (available in Development Tools) and Chrome (add the Colorblindly extension).
Misconceptions about Color Blindness
Color blindness doesn’t necessarily mean you can only see shades of gray. Depending on the type, most colorblind people can see color.
However, some colors may look faded. Colors may also look different to someone with color blindness than to someone with normal color vision.
Sometimes, people may not be aware they have a color vision deficiency until others point out that they do not see the right color. Or, they may not discover their condition until a doctor tests their color vision.
Difficulties of Color Blindness
Although there are plenty of colorblind people who live comfortably with the condition, it can still affect a person’s day to day life.
Some people who experience the greatest problems include:
- People who play sports
- People who work in retail or any job that requires matching colors for customers
- Anyone who needs to identify certain types of signal lights (especially maritime or aviation)
- Artists, designers, and others who rely on color vision to perform their work
- Drivers who are unable to tell the difference between red lights and green lights
Can Color Blindness Be Treated?
There is no cure for color blindness. However, specialty lenses can enhance and minimize any color vision deficiency. They’re available as glasses or colored lenses.
These lenses can be life-changing for people with difficulty performing daily activities because of color vision deficiencies. They’re also useful for professionals who must pass color deficiency screenings at work.
EnChroma glasses are specially designed to enhance vision in people who are red-green color blind. They carry a wide assortment of glasses to suit mild, moderate, and severe levels of color blindness.
Colormax is a company that produces contact lenses (colored lenses) and glasses for colorblind people. Their ColorCorrection System uses customized filters that are unique for every person.
Is Color Blindness a Disability?
In the U.S., color blindness is a disability according to the Americans with Disabilities Act (ADA). This means that employers must provide reasonable accommodation for their colorblind employees.
People who are color blind can also apply for disability through the Social Security Administration (SSA). They qualify if the condition causes them not to be able to work or find employment for more than a year.
U.S. citizens who are completely or partially color blind also qualify for a “color blind allowance” from the government.
In this article