Color Blindness: Types, Tests, and More

Have you ever looked at something and realized the colors just don’t seem quite right? For people with color blindness, that’s a daily experience. Whether it’s mixing up red and green or struggling with shades of blue and yellow, color blindness can make everyday tasks a bit trickier. With the right tools and tips, it’s absolutely manageable.

What is Color Blindness?

Color blindness, also called color vision deficiency, is an eye condition in which a person cannot tell the difference between certain colors. For example, a person might find it hard to tell the difference between certain shades of reds and greens or blues and yellows. True color blindness, where everything appears black and white or shades of gray, is very rare and is called achromatopsia. Color blindness usually affects both eyes equally and does not get worse over time.

Prevalence of Color Blindness

Yes, studies suggest that 1 in 12 men or about 8% of men with Northern European ancestry have red green color blindness. The condition is less common in women, affecting about 1 in 200 (0.5% of women). Blue yellow color blindness is much less common, occurring at a rate of about 1 in 10,000 people.

What Causes Color Blindness in Humans?

The retina is the light-sensing layer at the back of the eye. It contains two types of nerve cells called rods and cones. Rods detect light and dark, and cones detect color. Different types of cones detect different primary colors – red, green, and blue. Color blindness develops if there are problems with one or more of the cone cells, i.e., the cone cells are absent, do not work properly, or detect the wrong color.

Risk Factors

• Gender: Color vision defects are much more common in males compared to females.

• Family history: A genetic mutation (change in the DNA) causes red green colour blindness in humans. This gene mutation is passed from parents to their offspring. Red-green color blindness, which is the most common type of color blindness, has a sex-linked (X-linked) recessive inheritance pattern. As a result, it commonly affects males and is rare among females.

• Exposure to chemicals: Exposure to welding lights and neurotoxic chemicals such as organic solvents and heavy metals is linked to color blindness.

• Medical conditions: Certain conditions can increase the risk of color vision deficiency, for example, macular degeneration, glaucoma, diabetes, sickle cell anemia, Alzheimer's disease, Parkinson's disease, multiple sclerosis, leukemia, and chronic alcoholism. When the cause is an underlying disease, color blindness symptoms may be worse in one eye compared to the other. This form of color blindness may improve when the underlying disease is treated.

• Medications: Certain medicines can cause color vision defects, such as hydroxychloroquine, which is used to treat rheumatoid arthritis and malaria.

• Eye damage: Trauma to the eye from injuries, radiation therapy, surgery, or laser treatment can cause color blindness in some people.

What Are The Types of Color Blindness?  

People with normal color vision have three types of cones in their retina:

• L cones that sense red or long wavelengths of about 560 nanometers. 

• M cones that sense green or intermediate wavelengths of about 530 nanometers.

• S cones that sense blue or short wavelengths of about 420 nanometers.

Color vision is broadly classified as follows:

• Trichromacy: Full and normal color vision with all three types of cones being present and working properly. 

• Anomalous trichromacy: All three types of cones are present but one type isn’t working properly, causing color perception difficulty with pale and muted colors.

• Dichromacy: One type of cone is missing, making it hard for the color blind person to see even fully saturated colors.

• Monochromacy: Only one type of cone is present, resulting in severe color vision defects with only shades of gray visible.

Red-Green Color Blindness  

This is the most common form of color blindness. It makes it difficult to tell the difference between shades of red and green. This type is more common in males because the genes for the cones are present on the X chromosome (males have only one X chromosome while females have two).

Blue-Yellow Color Blindness  

This is a less common form of color blindness. It makes it difficult to tell the difference between shades of blue and yellow. Both males and females are equally affected.

What Is The Rarest Color Blindness?

The rarest color blindness is blue cone monochromacy that affects 1 in 100,000 people. People with blue cone monochromacy have only S cones present with L and M cones absent. This results in everything appearing in shades of light and dark gray. 

Another rare form of color blindness is achromatopsia (rod monochromacy), which affects 1 in 30,000 people. In this form, all or most cones are missing or dysfunctional, resulting in everything appearing in shades of gray.

Complete color blindness is rare. Most people have mild color deficiencies. This means they can distinguish between colors normally in bright light but have difficulty doing so in low light. Others with more severe color blindness cannot tell colors in any light. 

Common Symptoms of Color Blindness

Color vision deficiency is usually detected during childhood (typically children ages 4 and up) when a child is easily confused between shades of red and green, shades of blue and yellow, or any colors, depending on the cone types affected. 

For example, affected children may have problems telling the colors in traffic lights or learning with color-coded materials in the same way as a child with normal color vision.

A severe form of color blindness (blue cone monochromacy) can result in other symptoms such as photophobia (light sensitivity), myopia (nearsightedness), and nystagmus (abnormal eye movements).

Colour blind people face many difficulties in daily life during routine activities such as driving, preparing food, shopping, sports, gardening, and selecting outfits.

Diagnosis of Color Blindness

Ishihara Test  

If you have symptoms of color blindness, an eye care professional can do a comprehensive eye exam and a color blind test called the Ishihara test. This test can help your eye doctor find out if you have normal vision for red light, green light, and blue light, or if you have a color vision deficiency. 

The Ishihara test involves looking at special pictures that have dots with shapes and numbers in different colors hidden within them. People with a color vision deficiency find it difficult to see the hidden digit or pattern within the dots. 

Reverse Color Blind Test

As noted, some Ishihara plates have numbers or shapes that are only visible to people with full color vision. Others have numbers or shapes that are easily visible to those with a color vision deficiency but not to those with normal color vision – these are called reverse color blind tests.

Other Diagnostic Methods  

Based on the findings of the Ishihara test, your eye care provider may recommend further testing to rule out other conditions, confirm a diagnosis of color blindness, and assess what type of color vision is affected.

Can You Be Partially Color Blind?

Yes, you can be partially color blind. Color blindness isn’t a single condition but a range of color deficiencies across a broad spectrum based on certain cones being absent or non-functional.

For example, some people have difficulty distinguishing between dull and muted colors but do well with telling bright colors apart. In some people with color blindness, the red-green color vision defect makes certain shades of green look more red or certain shades of red look more green. But these changes are mild and don’t usually interfere with normal activities.

Tips For Managing Color Blindness  

There is no treatment or cure for most types of color perception difficulties (inherited forms). If the color vision problem is from the use of certain medicines or underlying health conditions, stopping the medication or treating the underlying condition may improve the ability to see certain color combinations. 

Wearing colored filters over eyeglasses, special glasses, or special contact lenses can boost the perception of different shades of colors. However, such tools cannot improve the ability to see all the colors in the visible spectrum.

The vast majority of people with color blindness rely heavily on the following coping strategies to identify colors and avoid color clashes:

• Using color vision aids to see colors differently.

• Labeling objects.

• Using technology such as smartphone apps.

• Utilizing adaptive techniques like memorizing patterns or contrasting colors.

• Educating others about the condition. 

• Considering career paths that are less reliant on color discrimination.

Is Color Blindness a Disability?

Color blindness may be considered a disability under the Americans with Disabilities Act (ADA) if the red-green or blue-yellow color deficiency significantly impacts daily life or the ability to perform certain jobs, such as aviation, electrical work, or graphic design.