Color blindness is primarily caused by inherited genetic mutations that affect the light-sensitive cone cells in your retina. Most people with color vision deficiency are born with it, but aging, eye diseases, and certain medications can also cause it later in life. The most common form is red-green color blindness, which affects about 8% of men and 0.5% of women of Northern European ancestry.
What exactly happens in the eye to cause color blindness?
Your retina contains two main types of light-sensing cells: rods and cones. Rods handle vision in dim light. Cones handle color vision and detail.
You have three types of cones, each sensitive to different wavelengths of light:
- L-cones – sensitive to long wavelengths (reddish light)
- M-cones – sensitive to medium wavelengths (greenish light)
- S-cones – sensitive to short wavelengths (bluish light)
Color blindness happens when one or more of these cone types are missing, fewer in number, or not working properly. The brain then receives incomplete or altered color signals. This is not a problem with the eye itself in most cases — it is a problem with how the retina processes color.
What Causes Color Blindness Genetics Aging More?
Genetics is the most common cause. The genes that code for L- and M-cone photopigments are located on the X chromosome. Because men have only one X chromosome, a single faulty copy of the gene causes color blindness. Women have two X chromosomes, so they usually need two faulty copies to be affected — which is why color blindness is far more common in men.
The inherited form is present from birth and remains stable throughout life. It does not get worse over time. The most frequent type is deuteranomaly — a shift in the sensitivity of the M-cones that makes green and red look similar.
Aging can also cause color vision to change. The lens of the eye yellows over time, which can reduce the ability to distinguish blues and purples. This age-related change is usually mild and affects both eyes equally. It is not true color blindness but a gradual loss of color discrimination.
Other causes include eye diseases and conditions that damage the retina or optic nerve. These are covered in the next sections.
What are the main types of inherited color blindness?
Color blindness is divided into types based on which cone class is affected.
Red-green color blindness is the most common. It includes:
- Deuteranomaly – green cones are present but less sensitive. Green and red appear similar.
- Deuteranopia – green cones are completely missing.
- Protanomaly – red cones are less sensitive.
- Protanopia – red cones are completely missing.
Blue-yellow color blindness is much rarer. It involves the S-cones. Tritanomaly means blue cones are less sensitive; tritanopia means they are missing. These forms are not sex-linked — they are inherited through a different gene on chromosome 7, so they affect men and women equally.
Monochromacy is the rarest type. The person has only one functioning cone type or none at all. This causes very poor overall vision and extreme light sensitivity. It affects about 1 in 30,000 people.
Can color blindness be caused by aging?
Yes, but the mechanism is different from inherited color blindness. With aging, the lens of the eye becomes less clear and may take on a yellowish tint. This filters out some blue light and makes it harder to tell the difference between blues, greens, and purples.
This age-related change is gradual and usually mild. Most people do not notice it as a disability. It is not a true deficiency of the cone cells themselves. Instead, it is a filtering effect by the lens.
Age-related macular degeneration (AMD) can also affect color vision. AMD damages the macula, the central part of the retina where cone density is highest. People with advanced AMD may notice colors look less vibrant or washed out. This can occur in both dry and wet forms of the disease.
What medical conditions can cause acquired color blindness?
Several eye diseases and systemic conditions can damage the retina or optic nerve, leading to color vision loss. Unlike inherited forms, acquired color blindness can affect one eye more than the other and may worsen over time.
Common causes include:
- Diabetic retinopathy – damage to blood vessels in the retina can affect cone function.
- Glaucoma – increased eye pressure damages the optic nerve, often first affecting color discrimination, especially blue-yellow.
- Optic neuritis – inflammation of the optic nerve, often associated with multiple sclerosis, can temporarily or permanently reduce color vision.
- Retinitis pigmentosa – a group of inherited retinal diseases that cause progressive loss of rod and cone function.
- Parkinson’s disease – some research suggests that color contrast sensitivity can decline, possibly due to dopamine loss in the retina.
- Alzheimer’s disease – visual processing changes can include altered color perception, though this is not a primary symptom.
If you notice a sudden or progressive change in your color vision, it is important to see an eye doctor. Acquired color blindness can be a sign of a treatable underlying condition.
Can medications or toxins cause color blindness?
Yes. Some prescription drugs and chemical exposures can interfere with how cones function or damage the retina.
The most well-known example is hydroxychloroquine (Plaquenil), a medication used for rheumatoid arthritis and lupus. Long-term use can cause retinopathy that first affects color vision. Regular eye exams are recommended for people taking this medication.
Other drugs that may affect color vision include:
- Ethambutol – used for tuberculosis; can damage the optic nerve and cause red-green color deficits.
- Sildenafil (Viagra) and tadalafil (Cialis) – in high doses, these can cause a temporary bluish tint to vision. This is usually harmless and reversible.
- Digoxin – a heart medication; toxicity can cause yellow-green color changes.
- Some anticonvulsants and antipsychotics – may have effects on color perception, though evidence is less consistent.
Chemical exposures, such as to carbon disulfide or lead, can also damage the optic nerve and affect color vision. These are more common in occupational settings.
How is color blindness diagnosed?
The standard test is the Ishihara color plates. You look at a circle of colored dots and try to identify a number or shape embedded within. People with red-green color blindness will see a different number or no number at all. This test is quick and widely used.
For more precise diagnosis, an eye doctor may use the Farnsworth-Munsell 100 Hue Test. You arrange colored caps in order of hue. The pattern of errors identifies the type and severity of the deficiency.
Genetic testing can confirm the specific mutation, but it is rarely needed for management. Most people with color blindness do not require treatment because there is no cure — it is a lifelong condition. However, special tinted glasses and contact lenses may help some people distinguish colors better in certain situations. These do not restore normal color vision and are not a cure.
How does color blindness affect daily life?
For most people, inherited color blindness causes mild to moderate inconvenience. Common challenges include:
- Telling apart red and green traffic lights — but the position usually helps.
- Reading color-coded charts or graphs.
- Matching clothing or identifying ripe fruit.
- Interpreting electrical wiring colors (red/green).
Children with color blindness may struggle in school with colored worksheets or activities. Early screening can help teachers and parents provide support. Most people adapt well and learn to rely on brightness, position, and context rather than color alone.
Certain professions have color vision requirements — for example, pilots, electricians, and some law enforcement roles. If you have color blindness, you can still succeed in many careers, but you may need to check specific requirements early.
Is there any treatment or cure for color blindness?
There is no cure for inherited color blindness. Gene therapy has shown promise in animal studies and very early human trials, but it is not available as a standard treatment. No large human trials have confirmed a safe, effective cure.
Tinted glasses and contact lenses (such as EnChroma glasses) filter certain wavelengths of light to enhance contrast between red and green. Some people report improved color discrimination while wearing them, but results vary. These glasses do not give you normal color vision — they simply shift the colors you see. They are not a treatment and do not change the underlying biology.
For acquired color blindness, treating the underlying cause may improve color vision. For example, stopping a toxic medication or controlling diabetes can prevent further damage. In some cases, color vision may partially recover.
Frequently Asked Questions
Can color blindness develop later in life?
Yes. Aging, eye diseases like glaucoma or macular degeneration, and certain medications can cause acquired color vision deficiency. This is different from inherited color blindness and may affect one eye more than the other.
Is color blindness more common in men or women?
Red-green color blindness is much more common in men because the responsible genes are on the X chromosome. About 8% of men and 0.5% of women have it, though rates vary by ancestry.
Can you be color blind in only one eye?
It is very rare for inherited color blindness to affect only one eye. However, acquired color vision loss from trauma, disease, or medication can affect one eye independently.
Do color blind glasses actually work?
Some people report improved color discrimination with tinted glasses, but the effect varies. They do not correct the underlying deficiency and are not a cure. They simply filter light to enhance contrast between certain colors.
