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Why do color deficiencies happen?

Color vision deficiency (CVD), also known as color blindness, is the decreased ability to see color or differences between colors. It affects a significant percentage of the population worldwide. Understanding the causes and types of CVD can help people better support those with color vision challenges.

Color vision allows us to appreciate the beauty and vibrancy of our surroundings. For most people, color vision comes naturally. But for those with CVD, their world appears duller and less vivid. This article will explore what causes deficiencies in color perception and the different forms it can take. Gaining insight into CVD supports inclusion and accessibility for those living with it.

How color vision works

Normal color vision relies on specialized receptor cells in the retina called cones. There are three types of cones, each sensitive to different wavelengths of light corresponding to particular colors:

  • S cones – short wavelength (blue)
  • M cones – medium wavelength (green)
  • L cones – long wavelength (red)

The combination of signals from these three cone types allows the perception of the full spectrum of colors. Deficiencies in any of the cone types will lead to problems differentiating certain shades.

Causes of color vision deficiencies

CVD occurs due to issues with the development or function of the cone photoreceptors. Several factors contribute to these problems:


Defective color vision genes can be inherited from a person’s parents. The most common forms have a hereditary basis. Depending on the specific mutation, defects may affect one, two, or all three cone types.


As people get older, the lenses in their eyes gradually yellow. This filters out some blue light, making it harder to distinguish some blue/violet hues. The cones themselves also deteriorate over time.


Certain illnesses like diabetes and multiple sclerosis can damage the optic nerve or cones in the retina. Trauma to the eyes or head can also impair color perception.


Some drugs are toxic to the retina and lead to vision changes. These include medications like chloroquine, tamoxifen, and thioridazine.

Environmental factors

Exposure to industrial chemicals, lead, and smoking have associations with acquired color vision defects later in life.

Types of color vision deficiencies

There are various forms of color blindness depending on which photoreceptor types are impacted:

Red-green color blindness

This is the most prevalent type, affecting around 1 in 12 men and 1 in 200 women globally. It occurs when the M or L cones are absent or not functioning normally. Red, orange, yellow, and green hues may be confusing and hard to tell apart.

Blue-yellow color blindness

A rare condition where there are issues with the S cones. Blues look greener, while yellows look redder or pinker. Purples may appear dark red.

Complete color blindness

When two or more cone types are non-functional, it leads to an inability to perceive any color. Vision is shades of grey, like black and white television.

Type Cone defect Problem colors
Red-green M or L cones Reds, greens, oranges, browns
Blue-yellow S cones Blues, yellows, violets
Complete color blindness Two or more cone types All colors

This table summarizes the common color vision deficiencies, the associated cone defects, and the hues they have trouble distinguishing.

Diagnosing color deficiencies

Several methods are used to evaluate color perception:

Color vision testing

This employs panels such as pseudoisochromatic plates or arrangement tests. The person identifies numbers or patterns made up of colored dots. It allows quick assessment of the type and severity of CVD.

Retinal imaging

Special cameras can visualize the living retina in fine detail. The appearance and density of the cone photoreceptors can reveal defects.


By placing electrodes around the eyes, this technique measures cone responses to colored lights flashed into the eye. Abnormal results confirm the cones are not functioning correctly.

Genetic testing

Identifying mutations in genes involved in color vision offers definitive proof for a hereditary basis underlying the CVD.

Prevalence of color vision deficiencies

Reliable statistics on CVD prevalence come from population-based studies:

Country Men affected Women affected
United States 1 in 12 1 in 200
Europe 1 in 12 1 in 250
China 1 in 20 1 in 500
South Africa 1 in 8 1 in 50

This table shows the approximate rates of color blindness in selected countries based on large studies. There is consistent male predominance worldwide.

Impact of color vision deficiencies

CVD can mildly or severely affect everyday function:

Difficulty with colors

Those with CVD struggle to distinguish colors in the problematic parts of the spectrum. This can make certain tasks stressful or dangerous.

Issues in school and work

Color coding is widely used in education andoccupations. Charts, diagrams, wires, and computer screens pose challenges.

Problems with driving

Interpreting traffic lights and signs, as well as assessing brake and indicator lights on other vehicles becomes difficult.

Limitations in hobbies

Many activities like arts, crafts, gardening, sports, and cooking rely on discerning colors accurately.

Social and emotional effects

There is sometimes stigma, assumptions of dishonesty, and reduced career options due to color blindness.

Living with color deficiencies

Though challenging at times, there are many ways to successfully adapt:

Specialized tinted lenses and filters

These eyedrops and glasses optimize colors by blocking certain wavelengths that cause confusion.

Alternative color naming

Using descriptive color names like light green vs dark green is more definitive than only green.

High contrast and minimal color-coding

Adjusting visual environments and designs boosts accessibility for those with CVD.

Support groups

Online forums allow people to share experiences and helpful tips.

Raising awareness

Educating others fosters empathy and inclusion for people with color vision deficiencies.


Color vision defects result from genetic, age-related, pathological, and environmental causes. They can significantly impact lives, but accommodations and new technologies are improving accessibility. Understanding why color blindness occurs allows us to better support those living with CVD and make environments more inclusive. With some creative adaptations, people with color deficiencies can find personalized ways to thrive in a vibrant multicolored world.