Definition & Overview

Color vision deficiency is a condition that renders a person incapable of distinguishing certain shades of color. In severe cases, the person may not see any color at all, which is a less common condition distinctly called achromatopsia. Color vision deficiency, or more popularly known as color blindness, is rarely severe but it does affect a large number of people at varying degrees. Instead of specific colors, patients usually only see gray where the colors are supposed to appear. Most of the time, it affects a person’s capacity to see the colors red and green, so they are unable to differentiate between them. The brightness or darkness of said colors will also determine how hard it is for them to tell between the two colors.

In less common cases, a person may not be able to differentiate between blues and yellows; this is considered as a more severe form of color vision deficiency because more often than not, people who cannot distinguish between blue and yellow will have compromised ability to tell between red and green as well.

Cause of Condition

The specific cause of color vision deficiency has a major effect on its severity. The most common causes include:

  • Heredity – When color blindness presents as a genetic condition, it usually affects both eyes and the severity remains constant all throughout a person’s life. Studies show that genetic color blindness is due to a common X-linked recessive gene that is commonly passed from mother to son, with women being the more common carriers but men having a greater risk of being born with it. This is the most common cause of this condition.

  • Injury – When caused by injury, this condition usually affects only the eye that was affected by the said injury. It could be just one eye or both, depending on the injury.

  • Medications – Certain medications, such as those used to treat hypertension, infections, heart problems, and other nervous or psychological disorders tend to cause color deficiency as a side effect.

  • Aging – In some people, the ability to distinguish among different colors tend to become compromised with age.

  • Exposure to chemicals – Color vision deficiency may arise as an occupational hazard usually among people who come in contact with fertilizers and styrene on a regular basis.

  • Illness – As with cases caused by injury, illnesses that cause color blindness may affect either one eye or both.

The common illnesses that may cause color deficiency are:

  • Diabetes
  • Macular degeneration
  • Alzheimer’s disease
  • Glaucoma
  • Multiple sclerosis
  • Parkinson’s disease
  • Leukemia
  • Sickle cell anemia
  • Chronic alcoholism

Color blindness occurs in the photoreceptors found in the retina. Known simply as cones, these photoreceptors contain light-sensitive pigments that are responsible for recognizing colors. Located in the central part of the retina and found in the macula, the cones are highly sensitive to red, blue, and green and send information to the brain through the optic nerve. In color vision deficiency, the cones lack one or more of these light-sensitive pigments.

Key Symptoms

The main symptom of a color vision deficiency is difficulty telling between two specific colors, namely red and green or blue and yellow. These colors are usually replaced by gray or neutral hues among colorblind patients.

The condition can be confirmed and diagnosed through a comprehensive eye exam using a series of pictures made up of several colored dots with figures or numbers hidden or embedded in them. These images are called pseudisochromatic plates. If a person is able to see the number or figure in the plates, he has normal vision. On the other hand, a person with color blindness will not be able to correctly see the embedded numbers or figures. This test is usually followed by other tests to determine the exact degree of the condition.

However, there is a challenge in diagnosing color vision deficiency especially when it is a genetic condition. Since children are taught that the leaves of trees are green, they will recognize the color of leaves as green, even though it does not really appear as the normal color of green in their eyes. Thus, both the child and parents will normally not suspect the condition, unless a specific situation causes a misunderstanding. This is the reason why many optometric organizations now support comprehensive eye testing among children before they begin going to school, as early detection of the condition may help patients to adjust to it more easily by incorporating this particular factor into how they begin to explore and familiarize with their surroundings.

Who to See & Types of Treatments Available

Color vision deficiency can be treated and color vision can be improved, but only when the condition is caused by illness or injury. In genetic cases, the condition does not have a cure. Thus, the only thing that can be done is to compensate for the loss of color vision in other ways. One of the most common ways used to do this is wearing specially designed tinted eyeglasses or tinted contact lenses. This may help improve color vision but may not capture the exact color.

Some patients also work around their condition by using external color cues. They can label their clothes or other colored objects with the assistance of their family and friends to help them recognize objects based on their color, or they can use other methods of remembering things instead of relying on their color.

Color vision deficiency may cause a lot of frustration for a person, given that it can also limit their ability to participate in certain activities or to work in some industries or fields. Although it does not seriously threaten a person’s ability to see, it is a condition that has to be adjusted to. It may also require time, patience, and the cooperation of immediate companions. With practice and patience, a person with color vision deficiency may be able to live as normally as possible.

References:

  • Adams AJ, Verdon WA, Spivey BE. Color vision. In: Tasman W, Jaeger EA, eds. Duane's Foundations of Clinical Ophthalmology. 2012 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:vol. 2, chap 19.

  • Berson EL. Visual function testing: clinical correlations. In: Tasman W, Jaeger EA, eds. Duane's Foundations of Clinical Ophthalmology. 2012 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:vol. 2, chap 14.

  • Wiggs JL. Molecular genetics of selected ocular disorders. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, MO: Mosby Elsevier; 2008:chap 1.2.

  • Sieving PA, Caruso RC. Retinitis pigmentosa and related disorders. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, MO: Mosby Elsevier; 2008:chap 6.10.

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