
Human eyes have two types of photoreceptors (cells that sense light and dark) in the retina (a sensory tissue layer that lines the inner surface of the back of the eyeball), namely, rods and cones.
- Rods are sensitive to low light and detect light and dark, whereas cones are responsible for color perception and are sensitive to the different wavelengths of light.
- There are three types of cones to identify various colors: S-cones (short wavelength for blue), M-cone (medium wavelength for green), and L-cones (long wavelength for red).
A person with normal color vision has trichromacy, which means a normal amount of all three cone types.
Depending on the type of cones that are deficient, color blindness may be of the following different types:
- Red-green color blindness
- A deficiency in green cones
- Deuteranomaly: A shift in the color sensitivity of the green cones.
- Deuteranopia: A complete lack of green cones.
- A deficiency in red cones
- Protanomaly: A shift in the color sensitivity of the red cones.
- Protanopia: A complete lack of red cones.
- A deficiency in green cones
- Blue-yellow color blindness
- A deficiency in blue cones
- Tritanomaly: A shift in the color sensitivity of the blue cones.
- Tritanopia: A complete lack of blue cones.
- A deficiency in blue cones
- Complete color blindness
- Dichromacy: Only two types of functioning cones are present.
- Anomalous trichromacy: All three types of cones are present, but one of the cone types is unable to detect color normally.
- Monochromacy or achromatopsia: Only one or none of the cones function normally.
- Tetrachromacy: A rare condition that allows an enhanced type of color vision.
What is color blindness?
Color blindness is a common condition in which there is a decreased ability to see or differentiate between certain colors. This usually happens between shades of greens and reds and, occasionally, blues.
Color blindness can be inherited (present at birth) or acquired (a result of the aging process, eye disease or injury, and certain medications).
This condition affects males more often than females and is estimated to be found in approximately 1 in 12 men and 1 in 200 women in the world.
Color blindness is also called:
- Color vision deficiency
- Defective color vision
What causes color blindness?
There are several causes of color blindness including:
- Inherited or genetic: The most common cause is mutations in the OPN1LW, OPN1MW, and OPN1SW genes, which are inherited from parents. These mutations can cause faulty photopigments and impaired color vision.
- Acquired: Some people may become color-blind due to other causes, such as
- Aging: The condition can be acquired over time due to the aging process.
- Diseases: Diabetes, multiple sclerosis, glaucoma, cataract, macular degeneration, Alzheimer’s disease, sickle cell anemia, and leukemia.
- Medications: Due to side effects of certain drugs, such as chloroquine or drugs to treat high blood pressure, infections, nervous, and psychological disorders.
- Chemicals: Can result from exposure to chemicals, such as organic solvents, carbon disulfide, and lead.
- Alcohol consumption: Reduced color discrimination can be a symptom of alcoholism.
- Physical cause: Damage or trauma to the optic nerve or parts of the brain.

SLIDESHOW
Pink Eye (Conjunctivitis) Symptoms, Causes, Treatments See SlideshowWhat are the signs and symptoms of color blindness?
The symptoms of color blindness can range from mild to severe, including:
- Trouble seeing or differentiating shades of colors
- Inability to differentiate brightness of colors
In rare cases, people can see only in shades of gray called achromatopsia, which is a condition often associated with:
- Nystagmus (rapid, uncontrollable eye movements)
- Light sensitivity
- Amblyopia (lazy eye)
- Poor vision
How is color blindness diagnosed?
Based on the symptoms, the ophthalmologist will conduct simple tests to determine if a person has color blindness.
- Color vision test or Ishihara color test: Contains 38 plates of circles created by irregular colored dots in two or more colors.
- Cambridge color test: Patients are told to find a “C” shape that is in a different color than the background on the computer screen.
- Anomaloscope: Used to measure quantitative and qualitative anomalies in color perception.
- Farnsworth-Munsell 100 hue test: Uses blocks or pegs of different shades of the same color.
Is color-blindness curable?
Currently, there are no medical treatments available for color blindness.
People with this condition learn to adapt and live with a relatively minor inconvenience. However, special glasses or corrective contact lenses may help people with red-green deficiency.
Treatment of the underlying medical condition may help resolve color vision deficiencies.
Health News
- Attachment Theory: What It Is, Stages & the Different Attachment Styles
- Gentle Parenting: What It Is, Techniques & Discipline
- U.S. Nursing Homes Fail to Report Many Serious Falls, Bedsores: Study
- The Younger You Get Diabetes, the Higher Your Risk for Dementia Later
- FDA Grants Full Approval to Paxlovid to Treat COVID-19
More Health News »
Health Solutions From Our Sponsors
Colour Blind Awareness. ·Colour Blindness. https://www.colourblindawareness.org/colour-blindness/
Huang M. Color blindness. Vision center. https://www.visioncenter.org/conditions/color-blindness/
Turbert D. What Is Color Blindness? American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/what-is-color-blindness
Seltman W. What Is Color Blindness? WebMD. https://www.webmd.com/eye-health/color-blindness
Medline Plus. Color vision deficiency. https://medlineplus.gov/genetics/condition/color-vision-deficiency/
Top What Are the Different Types of Color Blindness Related Articles
Are Lazy Eyes Genetic?
From a child’s birth until their 18th birthday, the brain and eyes form crucial connections. Genetics can play a role in causing lazy eyes. In case of a family history of amblyopia (lazy eye), it is better to consult an eye doctor at two years of age. Lazy eyes mainly occur in children and should be treated early.Color Blindness Picture
When we see different colors, we are perceiving differences in the light that is reaching our eyes. See a picture of Color Blindness and learn more about the health topic.Eye Health: Foods, Vitamins and Nutrients to Improve Eyesight
Eye Health: Foods, Vitamins and Nutrients to Improve EyesightEye Health: How to Relieve Tired Eyes
Lots of reading or screen time can leave your eyes tired, dry, and achy. Find out what you can do to ease eye fatigue.Eye Health: 11 Tips for Healthy Eyesight
Sharp eyesight is part of good health. Improve vision by eating well and scheduling regular eye exams with your ophthalmologist or optometrist. Certain medical conditions, like diabetes and high blood pressure, can negatively affect vision.Watery Eyes
Always tearing up? Everyday things can make your eyes water, but so can some medical conditions.Eye Conditions Quiz
What do you know about your eyes? Take this quick quiz to learn about a range of eye diseases and conditions.How Do You Get Rid of Puffiness Under the Eyes?
Bags and shadows under your eyes are a common occurrence. They make you look dull and haggard. The treatment strategy often depends on its cause, and the care may vary with every individual.How Do You Treat Dry Eyes?
Treatment for dry eye syndrome can include a range of home remedies and over-the-counter eye drops. For more severe cases, oral medication or surgery may be required.How Does Graves’ Disease Affect Your Eyes?
What is Graves' disease, and how does it affect your eyes? Learn the signs of thyroid eye disease, what causes it, and how it is treated.Sty (Stye)
A sty is a bump that forms on the eyelid as a result of a blocked gland. Styes may be caused by infections, burns, or trauma to the eyelid. Most styes resolve on their own. The application of warm compresses can speed healing. In some cases, steroid injection or incision and drainage may be necessary. Keeping the area clean and consuming a diet high in omega-3-fatty acids may help prevent the formation of styes.What Are the Best Eye Drops for Severe Dry Eyes?
Managing dry eyes usually starts with artificial tears. Learn about effective eye drop ingredients and how they work to relieve symptoms.What Causes Yellow Discharge From Eyes?
What is yellow discharge from your eye? Learn what causes it, how to recognize it, and how it is treated.What Is an X Mutation?
X-linked refers to any ailment that has an X chromosomal connection. Mammals normally have two copies of the X chromosome in females and one in males, which is referred to as a sex chromosome. Compared to the Y chromosome, which has only about 70 protein-coding genes, the X chromosome in humans contains about 800 protein-coding genes. The genes located in the X chromosome are referred to as X-linked genes.Why Are My Eyes Twitching?
Eye twitching, or blepharospasm, is a condition in which you cannot keep your eyes open for a long time due to spasms. The main causes of eye twitch include fatigue, stress, smoking, caffeine, medication side effects, light sensitivity, lack of sleep, foreign particles in the eye, and corneal irritation.Why Is Blue Light Bad for the Eyes?
Blue light is part of the visible light spectrum with the shortest wavelength and highest energy. It can pass straight to the retina of the eyes through the passage to the cornea and lens.