
What Are the Types of Color Blindness and Color Vision Deficiency? How Can You Tell?
Life is full of colors, but not everyone can perceive them the same way. Color blindness and red-green color vision deficiency are common visual impairments, and those affected may not even be aware of their condition. However, a quick test can determine if someone has color blindness or red-green color vision deficiency. But what types of color blindness and color vision deficiency are there, and how can they be diagnosed?

Color Vision Deficiency, Color Blindness, and Red-Green Color Vision Deficiency
Not all types of color blindness are the same. Depending on the cause and symptoms, color blindness can be classified as color vision deficiency, partial color blindness, or complete color blindness. These visual impairments can be either congenital or acquired. For example, eye conditions like macular degeneration can make it difficult for patients to distinguish colors. Long-term use of certain medications or diseases affecting the optic nerve can also lead to color vision problems, including optic nerve atrophy, where photoreceptor cells in the optic nerve die. The causes vary, including optic neuritis, increased pressure within the brain, or alcohol poisoning. Age-related lens clouding and changes in the brain can also limit our ability to perceive colors.
People with inherited color vision difficulties often discover their problem only after many years. It might be through casual conversations with people who have normal color vision ("I think that looks more blue..."), or during tasks that require precise color differentiation, that individuals with color vision deficiency realize that their perception of the world differs from others. Many professions require perfect color vision and do not accept individuals with color blindness or color vision deficiency, such as police officers, painters, painters, CAD software users, dentists, electricians, and laboratory assistants. Perfect color vision is also a requirement in many artistic, design, and fashion industries. Therefore, many professions require job applicants to undergo color vision testing, such as in the transportation industry. Future pilots and those applying for a boating license must also prove they are not colorblind.
Causes of Color Blindness and Color Vision Deficiency
The retina of the human eye has two types of photoreceptor cells: rod cells and cone cells. Rod cells mainly help us distinguish between light and dark, while cone cells are responsible for our color perception. People with normal vision have three types of cone cells, each responsible for a specific color range: L-cones for red, S-cones for blue, and M-cones for green. L, S, and M represent the different types of cone cells and the range of light they detect: L stands for "long" wavelengths, S for "short" wavelengths, and M for "medium" wavelengths. The wavelengths of light entering the eye stimulate pigments in the cone cells, triggering different color perceptions in the brain. If a certain type of cone cell doesn't function correctly or doesn't work at all, it limits our ability to perceive colors, leading to color vision deficiency or color blindness. Cone cells only operate under certain levels of brightness. In low light, only the rod system, responsible for light-dark contrast, is active. This explains why contrast is reduced in the dark.

Color Vision Deficiency, Such as Red-Green Color Vision Deficiency
People with color vision deficiency can only perceive certain colors because some of their cone cells do not function correctly. There are various types of color vision deficiency. The most common is red-green color vision deficiency, often (incorrectly) referred to as red-green color blindness or simply color blindness. About 9% of men and only 1% of women have this type of color vision impairment. Red-green color vision deficiency has two forms: difficulty distinguishing green (deuteranomaly) and difficulty distinguishing red (protanomaly). People with deuteranomaly struggle to recognize green because their green-sensitive cone cells are faulty. Compared to those with normal color vision, green appears less vivid and less dimensional to those with deuteranomaly, and they may only realize their visual impairment when they cannot distinguish different shades of green. Depending on the severity, individuals with green color vision deficiency may have difficulty distinguishing red and green, and sometimes even blue and purple or pink and gray—especially in low light. The symptoms of red color vision deficiency are similar: because their red-sensitive cone cells do not function correctly, individuals often have trouble distinguishing red or differentiating between red and green. Regardless of the type, there is no cure for red-green color vision deficiency.
Decreased Color Perception
Individuals with anomalous trichromacy, who have impaired color vision, still have all their cone cells present. However, these cells' sensitivity is severely limited, so the colors they perceive have lower saturation, making it difficult to distinguish colors. For example, those with limited red sensitivity may see a red light later than other drivers.
Partial Color Blindness, or Red-Green Color Blindness
People with partial color blindness lack or have non-functioning color-sensitive cone cells. Dichromats have only two types of cone cells, while monochromats have only one. These individuals cannot perceive the full color spectrum and can only recognize specific colors. For example, people with green color blindness (deuteranopia) lack green-sensitive cone cells, while those with blue color blindness (tritanopia) lack blue-sensitive cone cells. Those with red color blindness (protanopia) lack red-sensitive cone cells. As a result, they can only recognize a limited color spectrum. These individuals cannot distinguish red and green and may not recognize traffic signals or the red brake lights of the car ahead—or they may see them too late. Partial color blindness cannot be treated.
Complete Color Blindness
Complete color blindness (achromatopsia or achromasy) usually refers to inherited color blindness, where individuals can only perceive shades of gray and cannot see colors. The incidence of complete color blindness is roughly equal among men and women. Those with complete color blindness have significantly impaired vision and are extremely sensitive to light (photophobia). In complete color blindness, all three types of cone cells responsible for color perception do not function. These individuals rely entirely on the rod cells in their eyes, which are responsible for light-dark contrast perception. Therefore, people with complete color blindness can distinguish about 500 different shades of light and dark. Complete color blindness is mostly hereditary but can also result from strokes, brain injuries, or other brain damage.
What Should You Do If You Have Color Blindness?
There is no cure for color blindness or color vision deficiency. However, special glasses can alter color contrast, providing more comfortable vision in certain environments. Compared to regular lenses or sunglasses, glasses with red lenses can more effectively reduce glare to help those with red color blindness and increase their sensitivity to light. If a medication causes color blindness, the medication should be discontinued immediately.
Diagnosing Color Blindness and Color Vision Deficiency
Here are some color vision tests to determine if someone has color blindness or color vision deficiency.
Ishihara Color Blindness Test (Pseudoisochromatic Plate Test)
The Ishihara Color Blindness Test is used to diagnose red-green color vision deficiency or blue-yellow color vision deficiency (tritanomaly). The test consists of color plates made up of dots of different colors, with specific numbers hidden within the dots. The test determines the test subject's color vision ability by reading these numbers. For example, in the same color plate, a person with normal vision sees the number 74, while someone with red-green color vision deficiency sees the number 21. This method reliably diagnoses whether the test subject has a specific color vision deficiency.
Nagel Anomaloscope
The Nagel Anomaloscope is used to diagnose red-green color blindness or color vision deficiency. The device allows the test subject to mix red and green light into a specific shade of yellow (sodium yellow). This test method can accurately diagnose which type of color vision deficiency the patient has. For example, people with green color vision deficiency tend to add too much green.
Farnsworth-Munsell 100 Hue Test
This test is used to diagnose red-green color vision deficiency and blue-yellow color vision deficiency. The test involves arranging color chips in order. Depending on the type of color vision deficiency, the test subject tends to arrange them in a specific pattern, leading to conclusions about the specific type of color vision deficiency.
Take the Test: Are You Color Blind?
Many people have color vision deficiencies but are unaware of it—are you one of them? Take the test: What do you see in the 12 color plates below? Sometimes you can see the numbers, and sometimes you can't—compared to people with normal color perception, those with color vision deficiencies see different numbers or may not see any numbers at all. The "correct" answer—what someone with normal color vision would see—will be displayed when you hover over the color plate. If the number you see differs from the one shown, you may have a color vision deficiency. Eye care professionals can use specialized tests to determine if you have such a condition and confirm which type of color vision deficiency you have.







