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Grayson Bailey
Grayson Bailey

Ishihara Test 38 Plates.pdf

There are other color blindness tests available, but none of them is as famous as the Ishihara plates. It is also well known, that even people with normal color vision sometimes struggle with this test. But nevertheless this plates are still in use in the absence of any better and still affordable color vision test.

Ishihara Test 38 Plates.pdf

The Ishihara test is a color vision test for detection of red-green color deficiencies. It was named after its designer, Shinobu Ishihara, a professor at the University of Tokyo, who first published his tests in 1917.[2]

The test consists of a number of Ishihara plates, which are a type of pseudoisochromatic plate. Each plate depicts a solid circle of colored dots appearing randomized in color and size.[3] Within the pattern are dots which form a number or shape clearly visible to those with normal color vision, and invisible, or difficult to see, to those with a red-green color vision defect. Other plates are intentionally designed to reveal numbers only to those with a red-green color vision deficiency, and be invisible to those with normal red-green color vision. The full test consists of 38 plates, but the existence of a severe deficiency is usually apparent after only a few plates. There are also Ishihara tests consisting of 10, 14 or 24 test plates, and plates in some versions ask the viewer to trace a line rather than read a number.[4]

Born in 1879 to a family in Tokyo, Shinobu Ishihara began his education at the Imperial University where he attended on a military scholarship.[6] Ishihara had just completed his graduate studies in ophthalmology in Germany when war broke out in Europe and World War I had begun. While holding a military position related to his field, he was given the task of creating a color blindness test. Ishihara studied existing tests and combined elements of the Stilling test, named after the German ophthalmologist Jakob Stilling, with the concept of pseudo-isochromaticism to produce an improved, more accurate and easier to use test.[medical citation needed]

Proper testing technique is to give only three seconds per plate for an answer, and not allow coaching, touching or tracing of the numbers by the subject. The test is best given in random sequence, if possible, to reduce the effectiveness of prior memorization of the answers by subjects. Some pseudo-isochromatic plate books have the pages in binders, so the plates may be rearranged periodically to give a random order to the test.

Since its creation, the Ishihara Color Blindness Test has become commonly used worldwide because of its easy use and high accuracy. In recent years, the Ishihara test has become available online in addition to its original paper version.[citation needed] Though both media use the same plates, they require different methods for an accurate diagnosis.

The United States Navy uses the Ishihara plates (and alternatives) for color vision screening. The current passing score is 12 correct of 14 red/green test plates (not including the demonstration plate). Research has shown that scores below twelve indicate color vision deficiency, and twelve or more correct indicate normal color vision, with 97% sensitivity and 100% specificity. The sensitivity of the Ishihara test varies by the number of plates allowed to pass, which can vary by institutional policy. Sensitivity also may be influenced by test administration (strength of lighting, time allowed to answer) and testing errors (coaching by administrators, smudges or marks made upon the plates).

Colorblindness occurs in roughly 1 in 12 men and 1 in 200 women. Color deficiencies often pass down from our parents, rather than developing over time. Even though color blindness is more commonly an inherited condition, many people still live their lives without knowing they have a deficiency at all. Because vision is all about perception, many people with a deficiency do not realize they perceive colors differently than a person with average sight would. Therefore, getting tested for a color deficiency is important. There are many ways to test for a vision deficiency, but the more common method is the Ishihara test.

Shinobu Ishihara is the creator of the Ishihara test for color deficiency. Ishihara was a professor of Ophthalmology at the University of Tokyo and created the Ishihara test in 1917. The test originally came in three versions, two in Japanese and one in Arabic, to test the vision of soldiers in the Imperial Japanese Army. In later years, the third version of the test, written in Arabic, became widely available in the west. Since then, it has changed numerous times throughout the years to become the test we so often rely on today in color vision testing.

When taking the test, the goal is to identify the number on the plate. A person with perfect color perception would be able to identify all the numbers without issue. Different types of color deficiencies will see different numbers or no numbers at all, depending on the type of deficiency. In this way, this test can also help determine the specific type of deficiency a person may have.

Each test begins with a demonstration plate. The demonstration plate has a number that is visible to all types of color vision. This plate usually displays the number 12 and functions solely as an example to explain the test to those who are taking it. This plate does not count in the scoring of the test or diagnosis in any way.

Introduction: The Ishihara Test (IT) is arguably the most sensitive and commonly used color vision test within aviation and other occupational environments, but when no errors are allowed -20% of normal trichromats fail the test. The number of allowed errors varies in different occupations and sometimes within the same environment (such as aviation) in order to reflect the difficulties of the color-related tasks. The implicit assumption is that the plates can be ranked in order of difficulty. The principal aim of this study was to investigate whether appropriate "weights" can be attached to each IT plate to reflect the likelihood of producing a correct response. A second aim was to justify the use of color thresholds for quantifying the loss of red-green (RG) and yellow-blue (YB) chromatic sensitivity.

Methods: We investigated 742 subjects (236 normals, 340 deutans, and 166 protans) using the first 25 plates of the 38-plate IT and measured RG chromatic sensitivity using the Color Assessment and Diagnosis (CAD) test. The IT error scores provided plate-specific "weights" which were used to calculate a Severity Index (SI) of color vision loss for each subject.


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