COLOR BLINDNESS: CAUSES, TYPES, SYMPTOMS, TREATMENT AND MORE
Medically Reviewed by Dr. Sony Sherpa (MBBS) - September 25, 2024
A condition that impairs a person's ability to detect color appropriately is called color blindness or color vision deficiency. It is the most common inherited condition, affecting an average of 1 in 12 men and 1 in 200 women globally[1].
Despite its name, color blindness does not mean that a person can only see in black and white. Instead, it refers to a range of conditions that affect a person's ability to distinguish between certain colors.
In this article, we will explore what causes color vision deficiency, the different types, whether it can be acquired, and available treatments.
What Causes Color Blindness?
A genetic alteration that impacts the light-sensing cells in the retina of the eye is usually the cause of color blindness. These cells, called cones, are in charge of perceiving and interpreting various colors.[2]
There are three types of cones:
- Red-sensing cones (l cones)
- Green-sensing cones (m cones)
- Blue-sensing cones (s cones)
Each type of cone is sensitive to a different range of wavelengths of light, allowing us to see a wide spectrum of colors.
In people with normal color vision, all three types of cones work together to create a full range of colors. However, in people with color blindness, one or more types of cones are either missing or not functioning properly. This results in a reduced ability to see certain colors or a complete inability to see them.
Types of Color Blindness
Color blindness can be categorized under three main types:anomalous trichromacy, dichromacy, and monochromacy.
Most types of color deficiency cause varying degrees of red-green color deficiency or blue-yellow color deficiency.[3]
Anomalous Trichromacy
Anomalous trichromacy is the most common type of color vision deficiency, accounting for approximately 75% of all cases. In this type, all three types of cones are present, but one of them is not functioning correctly. This results in a reduced ability to distinguish between certain colors.
The types of anomalous trichromacy are protanomaly, deuteranomaly, and tritanomaly.
- Protanomaly: The red-sensing cones (l cones) are affected, lowering the ability to distinguish between red and green. Protanomaly is the most common form of anomalous trichromacy and color blindness overall.
- Deuteranomaly: Problems with the green-sensing cones (m cones) also impact the ability to differentiate between red and green colors.
- Tritanomaly: Blue-sensing cones (s cones) are deficient or faulty, causing blue and yellow colors to become confused.
Dichromacy
Dichromacy is a more severe form of vision deficiency where one type of cone is completely missing. This results in a person only being able to see a limited range of colors.
The three types of dichromacy are protanopia, deuteranopia, and tritanopia.
- Protanopia: Red-sensing cones (l cones) are missing, reducing the ability to see red light.
- Deuteranopia: Green-sensing cones (m cones) are lacking, affecting the perception of green light.
- Tritanopia: Blue-sensing cones (s cones) are deficient, impacting blue light.
Monochromacy
Monochromacy, also known as achromatopsia, is the most severe form of color blindness. In this type, two or all cones are missing, resulting in a person only being able to see shades of gray or blue.
Rod monochromacy and blue cone monochromacy are the two forms of monochromacy.
- Rod Monochromacy: Only the rods are present. Rods are responsible for detecting light and dark. Those with rod monochromacy solely perceive shades of gray.
- Blue Cone Monochromacy: Only the blue-sensing cones (s cones) are present. The person can only see shades of blue.
Symptoms of Color Blindness
The most common symptom of color vision deficiency is difficulty in distinguishing between certain colors. Some may have trouble telling different colors apart, while others cannot see certain colors at all.
Symptoms of red-green color deficiency:
- Having trouble distinguishing between red and green.
- Difficulties distinguishing between certain shades of orange, brown, and purple that contain red or green.
Symptoms of blue-yellow color deficiency:
- Problems distinguishing between blue and yellow.
- Being unable to tell the difference between blue and purple or between green and yellow.
Some people may also experience a reduced ability to see in low light conditions or have difficulty with color-related depth perception.
Color blindness is often easily diagnosable during childhood, during coloring, painting, or picking out clothing. Children may have difficulty identifying colors and matching colors or may use the wrong colors when attempting an artistic activity.
People with mild color blindness may not realize their condition until later in life.
Living With Color Blindness
Color deficiency can be a challenge for those with the condition in several areas of life. They may:
- Battle to wear matching clothes, select ripe fruit and vegetables, or read color-coded information.
- Face significant safety risks, such as being unable to interpret color-coded warning signs or traffic lights.
- Have fewer job choices and may not be able to pursue careers like graphic design, art, or jobs that need them to interpret colors.
- Need to remember the order of color-coded events or label items of color and learn to best use them.
Most people with color vision deficiency lead normal, healthy lives.
Regular eye exams and follow-ups with eye care professionals are important for those with color vision deficiency. These help to keep track of any changes in vision and to maintain eye health.
How Is Color Blindness Diagnosed?
Color blindness is diagnosed through a medical history, eye exam, and a color blind test, also known as a color vision test. This test assesses a person's ability to differentiate between different colors. An eye specialist will confirm the diagnosis after ruling out any other causes, such as eye disease or medications.
The color plate test (Ishihara test) is the most popular way to check for color blindness. It asks you to find numbers or patterns in circles with different colors. Others include the anomaloscope test and the hue test.[4]
The minimum age for a color-blind test can vary. In general, children as young as 4 or 5 years old can undergo a color-blind test. However, the accuracy of the test results may improve as children get older and their color vision fully develops.
Inherited vs. Acquired Color Blindness
Color deficiency is one of the most common genetic conditions globally. In some cases, it may also be acquired later in life.
Inherited Color Blindness
Inherited color blindness is passed down from parents who carry the genes for it on the X chromosome. Color vision deficiency genes include: CNGA3, CNGB3, GNAT2, OPN1LW, OPN1MW, ATF6, PDE6H, and PDE6C[5].
Color deficiency is more common in men than women, as men only carry one X chromosome. Women with one copy may not be color-blind, but are more likely to have a color-blind son.
Color-deficient women have genes on both of their X chromosomes. This means that both of their parents gave them a copy of the genes and that their fathers were also color-vision deficient.[6]
Acquired Color Blindness
Medications or eye diseases can lead to acquired color blindness.
The exact mechanisms of acquired color deficiencies are not fully understood. It is thought that medications and eye diseases can affect how color-sensitive cones in the eyes work, causing color vision deficiency.
This type is less common than the inherited type.
Health conditions associated with acquired color blindness include:
- Optic nerve neuropathy
- Age-related macular degeneration
- Cataracts
- Glaucoma
- Diabetic retinopathy
- Retinitis pigmentosa
- Macular edema
- Uveitis
- Retinal detachment
- Optic neuritis
- Eye injuries
- Brain tumors
- Neurological diseases like Alzheimer’s disease, Parkinson’s disease and multiple sclerosis
There may be other eye diseases or health conditions that are associated with acquired color blindness.
Medications that cause temporary color vision deficiency include[7]:
- Viagra (sildenafil) - treats erectile dysfunction.
- Amiodarone - stabilizes abnormal heart rhythms.
- Chloroquine - an antimalarial drug.
- Digoxin - used for heart failure and irregular heartbeats.
- Ethambutol - treats tuberculosis.
- Isotretinoin - prescribed for severe acne.
- Phenazopyridine - relieves urinary tract pain and discomfort
- Quinine - an antimalarial.
- Sulfasalazine - used for inflammatory bowel disease.
- Tamoxifen - chemo drug for breast cancer.
This list is not exhaustive, and color vision changes as a side effect of these medications are relatively rare.
The risk of color vision loss increases with aging, a lack of physical activity, chronic stress, consuming a high-fat or high-sugar diet, and leading a less healthy lifestyle.
If you suddenly lose the ability to see certain colors, it is advisable to consult with an eye care professional for proper diagnosis and treatment.
How Can I Prevent Color Blindness?
Below are some tips that may help reduce the risk of acquired color blindness. Inherited color blindness cannot be prevented or cured.
- Protect your eyes: Avoid eye injuries by wearing protective eyewear when doing activities that could hurt your eyes, like playing sports or working with dangerous materials.
- Be aware of medication side effects: If you are prescribed any medications, ask your doctor or pharmacist about their potential effects on color vision.
- Regular eye examinations: Regular eye check-ups can help detect any potential eye diseases or conditions that may lead to color vision loss. Early detection and treatment can help prevent further damage to your color vision.
If you are worried or have questions about color blindness, it is best to talk to an eye doctor for a correct diagnosis and advice.
Treatments for Color Blindness
At present, inherited color blindness has no known cure.[8]
There are some treatments available that can help people with color vision loss to see colors more accurately.
Color Blind Glasses and Contact Lenses
Color correction lenses and color correction glasses are available that claim to improve color vision.
They work by filtering out certain wavelengths of light, allowing the person to see a wider range of colors. These glasses are available in different tints, depending on the type of color vision deficiency a person has.
However, color-blind glasses and lenses may not work for everyone and are not suited to all types of color blindness. Despite anecdotal claims, some reviews suggest these are ineffective for improving color vision.
Color Detecting Smartphone Apps
There are several smartphone apps available that can aid those with color deficiency by helping them to identify colors.
Two examples of such apps are Color Blind Pal and Color Vision. These apps use the phone's camera to identify colors and provide real-time color correction. This helps color-blind users differentiate between different hues.
Acquired Color Blindness
In this case, treating the underlying condition or stopping the concerned medication after consulting with a doctor may help to improve color vision.
Latest Breakthroughs in Color Deficiency
Scientific advances in the treatment of color vision loss have shown promising results in recent years. In time, they may provide a cure to those with the condition.
Gene Therapy
Gene therapy is a cutting-edge treatment that aims to correct genetic mutations responsible for color vision deficiencies. By introducing healthy genes into the retina, researchers hope to restore normal color vision.
This approach has shown success in preclinical and clinical trials, providing hope for individuals with inherited color blindness. In one trial, researchers were able to get those with monochromacy who only saw in gray to see some shades of red as well.
More testing is needed to improve gene expression in different color vision problems and to make the technology perfect.
Bionic Eyes
Retinal prostheses, also known as "bionic eyes," are implantable devices that stimulate the retina to restore vision. Researchers are investigating the use of retinal prostheses in individuals with retinal degenerative diseases, including some forms of color vision deficiency.
Current bionics include the use of retinal implants coupled with eyeglasses that take pictures and feed them back wirelessly to the retina or to injections that amplify light receptivity. Although more research is needed, early studies have shown encouraging results.
Color Blindness Myths
There are many myths surrounding color vision loss and deficiency. It is important to dispel these myths to better understand the condition.
Myth: People With Color Blindness Can Only See in Black and White
As mentioned earlier, color blindness does not mean that a person can only see in black and white. Most forms of color deficiency make a person unable to perceive or distinguish between two or more colors. In the rarest cases, a person may only be able to perceive shades of blue or gray.
Myth: Color Blindness Means You Cannot See Red or Green
Color blindness does not mean a person cannot see red or green. The way color is perceived by a person with color deficiency depends on the type they have. Red-green color deficiency is the most common type, where someone has trouble telling the difference between red and green. It is also possible for those affected to have trouble seeing blue or yellow as well or to perceive no color at all (monochromacy).
Myth: Color Blindness Only Affects Men
While it is true that color blindness is more common in men, it can also affect women. Women have a lower chance of losing color vision as they carry two copies of the X chromosome.
Conclusion
Accurate perception of color is compromised by color blindness, commonly referred to as color vision deficit. The majority of cases are brought on by a genetic mutation that impacts the retina's light-sensitive cells. There are three main types: anomalous trichromacy, dichromacy, and monochromacy. While there is currently no cure, some people benefit from color correction lenses and glasses. Cutting-edge breakthroughs promise a cure in the next decade.
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