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, this severe form of the condition—in which you don't see colors at all—is rare. More accurate terms for color blindness are color vision deficiency and poor color vision.
About 8 percent of men are born with a color vision deficiency. It's less common in women, affecting only about 0.5%.
A color blind test is commonly used by optometrists and ophthalmologists to assess an individual's ability to distinguish colors accurately and identify any color vision deficiencies they may have.
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. Most people with this form of color blindness 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 this trait from her mother and have a father who's red-green colorblind.
You can also develop red-green color deficiencies from eye diseases that damage your retina or optic nerve.
People who are red-green colorblind tend to confuse purple and blue, as well as green, orange, and red.
There are three types of red-green color blindness:
1. Deuteranomaly
Most people who are red-green colorblind have this type. It makes green appear redder. This common form of color blindness is mild and usually doesn’t interfere with everyday tasks.
2. Protanomaly
This type makes red look more greenish and less vivid. It’s also mild and typically doesn’t interfere with daily activities.
3. Protanopia and Deuteranopia
Both these types make it impossible to tell the difference between green and red.
Blue-Yellow Color Blindness
The blue-yellow type of color blindness is rare. This type occurs in about 1 out of every 10,000 people and affects men and women equally. It causes problems distinguishing between yellow and red and between blue and green.
Most people get this type from an eye condition, such as:
Glaucoma
Optic neuritis
Diabetic retinopathy
Age-related macular degeneration
Central serous retinopathy
Optic nerve damage
The two types of blue-yellow color blindness are:
1. Tritanomaly
People with this type tend to confuse blue and green, as well as orange, yellow, and red.
2. Tritanopia
Tritanopia means you can’t tell the difference between these colors:
Blue and green
Purple and red
Pink and yellow
It also makes colors less bright.
What Causes Color Blindness?
Color blindness can be inherited or acquired. Inherited means the condition is passed on through genes and present at birth.
Acquired means that color blindness occurs later on in life. People can acquire color blindness in many ways, including:
Age-related changes
Eye diseases and injuries
Certain medications
Chemical toxicity
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)
Green light (medium wavelength)
Blue light (short wavelength)
A person with normal color vision has trichromacy, which means you have a normal amount of all three cone types. Someone with a color vision deficiency may lack all or some cones.
Types of Color Deficiency
Monochromacy
People with monochromacy (or achromatopsia) have the most severe color vision deficiencies. They don’t see color at all. Instead, they see everything in shades of gray, black, and white.
This happens because two or all three types of cone photopigments are absent. This type of color blindness is extremely rare, but people who live with it will often wear dark glasses to help protect their eyes.
Dichromacy
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.
People with dichromacy may be able to perceive color in bright- and normal-light situations, but their vision will deteriorate in poor lighting.
Anomalous Trichromacy
Anomalous trichromacy is considered color blindness to some extent, but it’s not 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 difficulties depend on which cone is faulty.
What Do Colorblind People See?
Typically, someone who is color blind has trouble seeing the difference between a red object and a green object. In some cases, they also have difficulty seeing blues or yellows.
Color blindness doesn’t necessarily mean you can only see shades of grey. Depending on the type, most people with color blindness can see color. However, some colors may look faded.
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.
Color Vision Testing
Ishihara Test
The most common type of color vision test eye doctors use is the Ishihara test. The test plates contain dots in various colors. Typically, there is a number on each test plate, although the dots could be arranged into other patterns. These are called pseudoisochromatic color plates.
Your eye doctor will ask you to identify what you see on each page. Those with color vision deficiencies may not be able to see any number or pattern on a given page.
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.
Arrangement Tests
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 more sophisticated assessments called arrangement tests.
The Farnsworth-Munsell 100-hue test provides more detailed information 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.
Can This 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 contact lenses.
These lenses can be life-changing for people with difficulty performing daily activities because of color vision deficiencies. People who might benefit from wearing them include:
Professionals who need to pass color vision screenings at work
People who play sports
Artists, designers, and others who rely on color vision to perform work
Summary
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—true colorblindness 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
There’s no cure for color blindness, but specialized lenses can help.