What is the iShihara test?

Ishihara test uses color boards to test the type and severity of color vision deficiencies. These deficiencies can range from the difficulties of distinguishing differences between specific colors to complete color blindness. The iShihara plate has a circle filled with colored dots. Usually there are dots in the background of one color and a figure made of dots of a different color. If a person testing the test cannot determine the character, probably has a lack of vision. During his job at the Japanese Military Faculty, who wanted to test problems with color vision at military recruits, he did the task of creating a graph of color vision. Graphs are still commonly used in eye tests around the world.

Color vision deficiencies are usually inherited and and and will be more often on men, but diseases, trauma or age can also cause color blindness. On the retina has tissue placed in the inner eye behind the pupil two types of buSomeone that accepts the light. The rod cells do not recognize color, but at night they work better and the conical cells recognize color and work better on the day. There are three types of cone cells in a healthy eye: S, which are sensitive to shorter wavelengths, M, which is sensitive to medium wavelengths and L, which is sensitive to longer wavelengths. The cones will pick up colors that fall within their range of wavelengths, with cone peaks in Fiala, the cones of the peak of greenery and l cone culminates on yellow.

The range of shades between these colors depends on the differences between the stimulation between the different cones. For example, when the cone L is very stimulated and the cones receive less stimulation, the eye perceives red. If one of these conical systems is damaged or missing, it will cause the lack of calLled dichromacia in which it may be difficult to distinguish some colors. If two of these cone systems are non -functional, it causes monochromacy, a rare condition in which the patient can only see gray shades. Dichromacia iMonochromacy is commonly called color blindness, although the term technically refers only to monochromacy.

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Ishihara test has a total of 38 plates, but only a few are used in a typical eye test. If, after a few boards, the patient is unable to distinguish a figure set into a colorful dot plate, evidence will usually be enough to diagnose a lack of color vision. Then a complete iShihara test can be carried out to see to what extent the patient's vision is disrupted and a damaged conventional system.

If the patient has dichromacy, it can be further diagnosed as protanopia, deuteranopia or rarely, tritanopia. People with Protanopia have a shortage of cones and limited sensitivity to red and people with deuteranopia have deficit cone and limited sensitivity to green. Tritanopia is caused by a lack of smokers S and leads to difficulty to distinguish the blue from the yellow. Ishihara boards that test red-green colored blindness or deficiency may have a number composed of red dots ofAsazed with many green dots or a green figure set with red dots. Patients with blue-yellow blindness or lack may have difficulty finding a yellow figure set with blue dots or a blue figure set with yellow dots in the iShihara test.