page_title: Color blindness
section_title: Diagnosis
hierarchical_section_title: Color blindness / Diagnosis
caption_attribution_description: English: An Ishihara test image as seen by able-bodied and by persons with a variety of Daltonism forms.
context_page_description: Color blindness, also known as color vision deficiency, is the decreased ability to see color or differences in color. Simple tasks such as selecting ripe fruit, choosing clothing, and reading traffic lights can be more challenging. Color blindness may also make some educational activities more difficult. However, problems are generally minor, and most people find that they can adapt. People with total color blindness may also have decreased visual acuity and be uncomfortable in bright environments.
  The most common cause of color blindness is an inherited problem in the development of one or more of the three sets of color-sensing cones in the eye. Males are more likely to be color blind than females, as the genes responsible for the most common forms of color blindness are on the X chromosome. As females have two X chromosomes, a defect in one is typically compensated for by the other, therefore non-colorblind females can still be carriers. Males only have one X chromosome and therefore always express the genetic disorder when possessing the recessive gene. Color blindness can also result from physical or chemical damage to the eye, optic nerve or parts of the brain.
context_section_description: The Ishihara color test, which consists of a series of pictures of colored spots, is the test most often used to diagnose red–green color deficiencies. A figure (usually one or more Arabic digits) is embedded in the picture as a number of spots in a slightly different color, and can be seen with normal color vision, but not with a particular color defect. The full set of tests has a variety of figure/background color combinations, and enable diagnosis of which particular visual defect is present. The anomaloscope, described above, is also used in diagnosing anomalous trichromacy.
  Position yourself about 75cm from your monitor so that the colour test image you are looking at is at eye level, read the description of the image and see what you can see!! It is not necessary in all cases to use the entire set of images. In a large scale examination the test can be simplified to six tests; test, one of tests 2 or 3, one of tests 4, 5, 6, or 7, one of tests 8 or 9, one of tests 10, 11, 12, or 13 and one of tests 14 or 15.
  Because the Ishihara color test contains only numerals, it may not be useful in diagnosing young children, who have not yet learned to use numbers. In the interest of identifying these problems early on in life, alternative color vision tests were developed using only symbols (square, circle, car).
  Besides the Ishihara color test, the US Navy and US Army also allow testing with the Farnsworth Lantern Test. This test allows 30% of color deficient individuals, whose deficiency is not too severe, to pass.
  Another test used by clinicians to measure chromatic discrimination is the Farnsworth–Munsell 100 hue test. The patient is asked to arrange a set of colored caps or chips to form a gradual transition of color between two anchor caps.
  The HRR color test (developed by Hardy, Rand, and Rittler) is a red–green color test that, unlike the Ishihara, also has plates for the detection of the tritan defects.
  Most clinical tests are designed to be fast, simple, and effective at identifying broad categories of color blindness. In academic studies of color blindness, on the other hand, there is more interest in developing flexible tests to collect thorough datasets, identify copunctal points, and measure just noticeable differences.
caption: An Ishihara test image as seen by subjects with normal color vision and by those with a variety of color deficiencies
exif: {}