Vision test, the Ishihara test is more specifically interested in the perception of colors. Today it is the most frequently used test worldwide to diagnose different types of color blindness.

Imagined in 1917 by the Japanese professor Shinobu Ishihara (1879-1963), the Ishihara test is a chromatic examination to assess the perception of colors. It makes it possible to detect certain failures related to color vision (dyschromatopsia) commonly grouped under the term color blindness.

The test is made up of 38 boards, made up of a mosaic of dots of different colors, in which a shape or number appears thanks to a unit of colors. The patient is therefore tested on his ability to recognize this shape: the color blind person cannot distinguish the drawing because he does not perceive its color correctly. The test is divided into different series, each geared towards a specific anomaly.

The test takes place in an ophthalmology office. The patient should wear his corrective glasses if he needs them. Both eyes are usually tested at the same time.

The plates are presented one after the other to the patient, who must indicate the number or the form he distinguishes, or the absence of form or number.

The Ishihara test is offered in case of suspicion of color blindness, for example in families of color blind (the anomaly being most often of genetic origin) or during routine examination, for example at the entrance to the school.

The test results help diagnose different forms of color blindness:

• protanopia (the person does not see red) or protanomaly: the perception of red is reduced
• deuteranopia (the person does not see green) or deuteranomaly (the perception of green is reduced).

As the test is qualitative and not quantitative, it does not make it possible to detect the level of attack of a person, and therefore to distinguish deuteranopia from deuteranomaly, for example. A more in-depth ophthalmologic examination will make it possible to specify the type of color blindness.

The test also cannot diagnose tritanopia (the person does not see the bruise and the tritanomaly (decreased perception of blue), which are rare.

No treatment currently makes it possible to alleviate color blindness, which moreover does not really cause a daily handicap, nor does it alter the quality of vision.