Color Blindness
Color blindness is an inherited or acquired condition in which the patient has difficulty telling apart certain colors or cannot see any colors...

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What Is Color Blindness?

Color blindness is the difficulty or inability to distinguish colors caused by problems with the color-sensing pigments in the eye. The majority of people who are colorblind cannot distinguish between red and green. Distinguishing yellows and blues may also be problematic, although this form of color blindness is less common.

The condition ranges from mild to severe. If you are completely colorblind (achromatopsia), you see only in gray or black and white. However, this condition is very rare. Most people with color blindness see yellow, gray, beige, and blue in color charts rather than the reds, greens, and teals that others see.

Color blindness is more common in men. Women are more likely to carry the defective chromosome responsible for passing on color blindness, but men are more likely to inherit the condition. According to the American Optometric Association, nearly eight percent of white males are born with color deficiency, in comparison to 0.5 percent of women (AOA).

Types of Color Blindness

There are three main types of color blindness. In the first, the person has trouble telling the difference between red and green. In the second, the person has difficulty telling yellow and blue apart. The third type is called achromatopsia. A person with this form cannot perceive any colors at all; everything appears gray. Achromatopsia is much more rare than the first two types.

Inherited vs. Acquired Color Blindness

Color blindness can also be classified as either inherited or acquired. Inherited color blindness is more common. It is caused by a genetic defect. This means that the condition is passed on through family—someone who has close family members who are colorblind is more likely to have the condition as well.

Acquired color blindness develops later in life and can affect men and women equally. Diseases that damage the optic nerve or the retina of the eye can cause acquired color blindness. For that reason, you should alert your doctor if your color vision changes—it might indicate a more serious underlying issue. Some of these underlying issues are discussed in the following section.

What Causes Color Blindness?

The eye contains nerve cells called cones that enable the retina, a light-sensitive layer of tissue in the back of your eye, to see colors. Three different kinds of cones absorb various wavelengths of light. Each cone reacts to a different color, namely red, green, and blue, and sends information to the brain to distinguish colors. If one or more of these cones in your retina has been damaged or is not present, you will have difficulty seeing colors properly.

Heredity

The majority of color vision deficiency is inherited, and is typically passed from mother to son. Inherited color blindness does not cause blindness or other vision loss. According to the National Institutes of Health, the condition is very rare in women, but some degree of color blindness occurs in 1 in 10 men (NIH, 2011).

Diseases

You can also have the condition as a result of disease or injury to your retina.

In glaucoma, the internal pressure of the eye (the intraocular pressure) is too high. The pressure damages the optic nerve, which carries signals from the eye to the brain so that you can see. As a result, your ability to distinguish colors may be diminished. According to the British Journal of Ophthalmology, the inability of people with glaucoma to distinguish blue and yellow has been noted since the 18th century (Pacheco-Cutillas & Edgar, 1999).

Macular degeneration and diabetic retinopathy cause damage to the retina, which is where the cones are. This causes color blindness and in some cases, blindness.

If you have a cataract, the lens of your eye gradually changes from transparent to opaque. Your color vision may be dimmed as a result.

Other diseases that affect vision include diabetes, Parkinson’s, Alzheimer’s, and multiple sclerosis.

Medications

Certain medications can cause changes in color vision. These include the antipsychotic medications chlorpromazine (Thorazine) and thioridazine (Mellaril).

The antibiotic ethambutol (Myambutol), which is used to treat tuberculosis, may cause optic nerve problems and difficulty seeing some colors.

Some heart and blood pressure medications, as well as medications prescribed for nervous disorders, can put individuals at an increased risk of developing acquired color blindness (Stresing, 2011).

According to the National Institutes of Health, the drug hydroxychloroquine (Plaquenil) can also affect color vision (NIH, 2011). This drug is usually used to treat rheumatoid arthritis.

Other Factors

Color blindness may also be associated with other factors. One factor is aging, in that vision loss and color deficiency can happen gradually with age. Additionally, toxic chemicals, such as styrene (which is used to make some plastics), have been linked to the loss of ability to see color.

Signs of Color Blindness

The most common symptom of color blindness is a change in your vision. For example, it may be difficult to distinguish between the red and green traffic light. Colors may seem less bright than before. Different shades of a color may all look the same.

Color blindness is usually detected at a young age when children are learning their colors. In some people, the problem goes undetected because they have learned to associate specific colors with certain objects. For example, they know that grass is green, so they call the color they see green. If symptoms are very mild, a person may not realize that they are not seeing certain colors. 

If you suspect color blindness in either yourself or your child, you should consult a doctor. A physician will be able to confirm the diagnosis and rule out other, more serious, health issues.

Testing for Color Blindness

Seeing colors is subjective. It is impossible to know whether you see reds, greens, and other colors exactly the same way as people with perfect vision. However, your eye doctor can test for the condition during a normal eye exam.

Testing will include the use of special images called pseudoisochromatic plates. These images are made up of small, colored dots that have numbers or symbols embedded within them that can only be seen by people with normal vision. If you are color blind, you may not see the number or may see a different number. It is important to have children tested before they start school, because many early childhood educational materials involve identifying colors.

Coping With Color Blindness

If color blindness occurs as the result of illness or injury, treating the underlying cause may help to improve color detection.

However, there is no cure for inherited color blindness. Your eye doctor may prescribe tinted glasses or contact lenses that can assist in distinguishing colors.

People who are colorblind often consciously apply certain techniques or use specific tools to make life easier. For example, memorizing the order of the lights from top to bottom on a traffic light removes the need to distinguish its colors. Labeling clothing can assist in matching colors properly. Some software applications transform computer colors into those that colorblind people can see.

Outlook

If you have inherited color blindness, it is a lifelong challenge. While it may limit prospects for certain jobs (for example working as an electrician who must tell the difference between color-coded wires) most people find ways to adjust to the condition.

Written by: Krista O'Connell
Edited by:
Medically Reviewed by: George Krucik, MD
Published: Jul 9, 2012
Published By: Healthline Networks, Inc.
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