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What Is [Color] Blindness?

Color blindness, also called color vision deficiency, occurs when a person’s ability to see certain colors is diminished. The term “color blind” is commonly used but not strictly accurate, since a person’s actual vision, apart from the inability to differentiate between colors, is not usually affected.

Males experience color blindness more often than females do, with 8% of men and 1% of women affected. The most common form of color blindness is difficulty distinguishing between shades of red and green, followed by blue and yellow. Usually, a person with this condition will be able to see some shades of these colors, but with less certainty or saturation as other people.

What Are Signs of Color Blindness?

Children who are color blind from birth usually don’t realize they have the condition until a parent or teacher detects a problem. If color blindness is caused by an illness or is a side effect of a medication, its onset may be sudden. This can occur in children and adults.

The following are common signs of color blindness:

  • Difficulty distinguishing different shades of red and green
  • Difficulty distinguishing different shades of blue and yellow
  • Certain colors consistently look unclear or washed out

People who find that their perception of color is compromised should schedule an appointment with an eye doctor promptly, since the gradual or sudden onset of color blindness could be a sign of cataracts or other serious eye conditions.

Causes of Color Blindness

Color blindness is caused by an absence of specific cones, nerve cells in the retina that detect light and are located in the back of the eye. The various cones detect wavelengths of light and send these messages to the brain through the optic nerve, where they are perceived as colors. If the cones are missing wavelength-sensitive chemicals, the ability to see green and red or blue and yellow is compromised.

The most common causes of colorblindness are:

  • Heredity–mothers who are carriers of color blindness can pass the gene to their sons. For a female to be color blind, both parents must have the gene.
  • Cataracts–when the eye’s lens becomes cloudy, colors can look muted. Surgery to replace the lens can correct the problem.
  • Parkinson’s disease–the neurological dysfunction caused by this condition can affect the cones in the eye.
  • Some medications–medicines to treat a variety of conditions such as blood pressure, autoimmune diseases and heart conditions can affect color differentiation. An anti-seizure drug, tiagabine, has been shown to reduce color vision in 41% of patients.
  • Leber’s hereditary optic neuropathy–can cause color blindness even for carriers of the disease.
  • Kallman’s syndrome–this disorder of the pituitary gland is characterized by color blindness, among other problems.
  • Chemical exposure–exposure to certain substances, such as carbon disulfide and certain fertilizers.

How is Color Blindness Diagnosed?

Color blindness is diagnosed through two main types of tests:

  • Ishihara color vision test–to determine the presence of color blindness
  • Farnsworth Munsell 100 hue test–an in-depth measure of the severity of the condition

The Ishihara color vision test was developed a century ago to detect red-green color blindness. It consists of 38 slides with many dots in various shades of colors. A person with normal color vision will be able to see the numbers that appear among the dots. Those with color blindness will not be able to detect all the numbers.

The Farnsworth Munsell 100 hue test is designed to determine the severity of color blindness. The subject must arrange colored disks on trays to show a sequence of the color progression.

Can Color Blindness Be Treated?

There is no cure for color blindness itself, but if it is caused by an underlying condition, such as cataracts, surgery will reverse it. A study published in Nature (2008) indicated that gene therapy could cure color blindness in monkeys. However this treatment has not yet proven as safe and effective for humans.

People with color blindness who become aware of their condition from a young age often learn adaptive behaviors to compensate for their inability to see colors. For instance, they will memorize the order of traffic lights or will arrange their clothing in certain categories to ensure their outfits match. Additionally, apps for Apple or Android can assist with differentiating colors.

Special glasses and contact lenses can assist some people with color blindness. These lenses use light-filtering technology that enable people with this condition to now see a wider range of colors.

If you or your child is showing signs of color blindness, schedule an appointment for an eye exam with in today.


How do color blind glasses work?

Color blindness is caused by the lack of specific photo pigments inside the cones located in the macular region of the retina. Special glasses or contact lenses compensate for this problem by altering the color saturation of certain objects to allow the brain to perceive the correct color.

How effective are color blind glasses?

Many varieties of glasses and contact lenses for color blindness are still being tested, with varying degrees of success. It should be noted that, since the lenses work with color saturation, only those who can perceive the problematic color pair to some degree will benefit from them.


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