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Color blindness/color vision deficiency is the inability to perceive differences in color that a normal person can perceive. The condition is most often inherited genetically, but it can also come about from chemical exposure, aging, or by the use of some medicines. Color vision deficiencies are seen in people all over the world. Though the condition may not present problems for some people, those who perform jobs where they need to detect color differences accurately may experience difficulties related to the condition. Therefore, it is advisable for people who suspect that they may have problems seeing certain colors to undergo color vision testing.
Color Vision Deficiency
Color vision deficiencies can come in several types. These can include problems with seeing the colors red, green, blue, and others. Problems with color vision may be inherited but may also be the result of aging, the use of certain medications, or the result of chemical exposure.
Color Vision Deficiency: Page from the University of Minnesota describing what color deficiency is, the known types, causes, plus links to more information.
Color Vision Deficiencies: Description of color vision deficiencies and example pictures that show what a color vision deficient person sees.
Color Vision Deficiency: Page from the American Optometric Association that defines color vision deficiency and talks about the causes, how it is diagnosed, and the treatment available.
Color Vision Deficiency: A page from the Optometric Physicians of Washington that describes color vision deficiency, particularly as it relates to children.
About color vision defects: Highly information page all about the different types of color vision deficiencies.
Explaining Color Deficiency: A page that describes the types of color deficiency and some of the genetics behind the condition.
Color-Blindness: A site that provides info on the various forms of color deficiency.
Achromatopsia
Achromatopsia is an inherited visual disorder that is caused by a retinal abnormality. Symptoms include decreased vision, sensitivity to light, and lack of color vision. There are two predominant forms of the disorder, complete achromatopsia and incomplete achromatopsia.
Achromatopsia: Basic information on achromatopsia that is geared towards parents.
The Achromatopsia Network: This is an information network for families and individuals affected by achromatopsia. The page contains links to further information about the condition.
Understanding Achromatopsia: Detailed information describing the condition of achromatopsia.
Incomplete and Complete Achromatopsia: A research paper that describes both complete and incomplete achromatopsia.
Achromatopsia: This page contains a list of links to sources on the web for more information and/or support groups for achromatopsia.
Pseudoisochromatic Testing Plates
Pseudoisochromatic testing plates are used to screen for color blindness/color vision deficiencies. Common screening plates include the Ishihara color plates and the Tritan color plates. Plates can be designed so that people who see colors normally can see one figure in a particular plate and those with abnormal color vision see something different in the same plate.
Color Vision Tests: Explanation of different types of color vision tests, including pseudoisochromatic testing plates.
New Pediatric Color Vision Test For Three to Six Year Old Pre-School Children: Article that describes pseudoisochromatic test plates specifically designed for color vision testing of young children.
Color Vision Testing: Examples of pseudoisochromatic testing plates.
Monochromacy
Monochromacy is known as total color blindness. It is the inability to distinguish between colors and is caused by a cone defect or an absence of cones. Examples of types of monochromacy are rod monochromacy and cone monochromacy.
Color Blindness: Page from the University of Illinois at Chicago that describes the cause and types of color vision defects, including monochromacy.
Monochromat: Article that details the cause and different types of monochromacy.
Blue-Cone Monochromacy: Information on blue-cone monochromacy from the Foundation Fighting Blindness.
Monochromacy: Complete Color Blindness: Information on the different types of monochromacy.
Dichromacy
Dichromacy is a type of inherited color vision defect. It occurs when a basic color mechanism is absent, does not function correctly, or when a cone pigment is missing and subsequently reduces color to only two dimensions. Protanopia, deuteranopia, and tritanopia are forms of dichromacy.
How do things look to the color-blind?: A highly informative report on the various types of color blindness, including dichromacy.
Color Blindness: Information on dichromacy and other types of color blindness.
Barrier-Free Presentation That is Friendly to Colorblind People: Article that discusses color blindness and how to prepare presentations in a way that makes them easy to read and understand for people with this condition.
What is Colour Blindness?: Facts about the various forms of color deficiency.
Anomalous Trichromacy
Anomalous trichromacy is a type of inherited color vision defect. This defect happens when a cone pigment becomes altered. The result is an impairment of trichromacy. Protanomaly, deuteranomaly, and tritanomaly are forms of anomalous trichomacy.
Colour-Blindness: Anomalous trichromacy and dichromacy explained.
Color Adaptation for Anomalous Trichromats: Research paper studying the effects of a color adaptation method for persons with anomalous trichromacy.
Congenital Colour Vision Deficiencies: Information on anomalous trichromacy and the other various types of color vision deficiency.
Ishihara Color Test
The Ishihara color test is a test created by Dr. Shinobu Ishihara that determines whether a person has red/green color blindness. The test is made up of colored plates that contain circles of differently shaped dots. Within each plate of dots there is a number that is also displayed as a pattern of dots. Persons with normal color vision can read the numbers, while those with red/green color blindness have difficulties or cannot see them at all.
Ishihara Test for Color Blindness: An online test to determine whether a person may have some color vision deficiencies that prompt further investigation by a professional.
Test for Colour Blindness: A simple test for determining color vision deficiencies.
Ishihara Color Blindness Test: Detailed information on color blindness, along with a tutorial that illustrates how persons with various types of color blindness perceive certain images.
Color Vision Test: Information for patients on color vision testing.
Color Blind Tests: Information about color screening tests such as the Ishihara color test.
Color blindness/color deficiency tests are important because they help people to determine whether or not they perceive colors normally. While many people with a color vision defect may not even be aware of it or struggle with it in their daily lives, those who have jobs that depend on accurate color perception or who wish to have such jobs in the future should be tested and be made aware of any deficits.
Color Vision Test: Online test to help people determine if they have color vision deficiencies.
Colour Blind Test: An online colour deficiency test from Spectacle World.
Free Online Color Vision Deficiency Test: An online test that can diagnose the three types of color vision deficiency.
Online Colour Vision Deficiency Test: Online color vision test from Coloryte.
Color Vision Deficiency Test: A color blindness eye check to determine whether a person may be suffering from this condition.
Color Vision Test: A color vision test that involves putting various colors into a sequence.
Color Blindness: Information about color blindness, along with a color blindness test.
Online Color Challenge: An online test to determine how well a person distinguishes different color hues.
Test for Color Blindness: An online version of the Neitz Test of Color Vision, a test for red/green color blindness.