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omarsetty   Comment Posted Feb.28th, 2023, viewed 116 times

HOW DO ISHIHARA COLOR BLIND TEST WORKS.

Ishihara’s color blindness detection chart is a method to detect color vision disorders, named after its inventor, Shinobu Ishihara, a professor at the University of Tokyo, Japan.

Ishihara’s earliest test map was published in 1917. At present, it has been recognized as the only color blind detection method by the International Organization for Standardization ISO.

One of Ishihara’s color blindness test. People with normal color vision can clearly see the number “74”. People with two-color color blindness or three-color vision abnormalities may see “21”, and people with total color blindness can’t see anything. number.

This test chart consists of a series of colored plate, called “Ishihara plate”, and each disc is filled with dots of various colors and sizes.

Some of the dots form one or several numbers in colors that are difficult for color-blind people to distinguish. People with normal color vision can easily distinguish these numbers, while those with color blindness cannot or are difficult to distinguish.

The full set of Ishihara’s inspection chart includes 38 color plates. Usually, only the first few color plates can be used to detect the color vision impairment.

After all the first 24 color plates are tested, the degree of color vision defects can be diagnosed more accurately.
Since then this is the most widely used color vision deficiency test and still used by most optometrists and ophthalmologists all around the world.

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.

There exist four different types of plates:

1. Vanishing design:
Only people with good color vision can see the sign. If you are colorblind you won’t see anything.

2. Transformation design:
Color blind people will see a different sign than people with no color vision handicap.

3. Hidden digit design:
Only colorblind people are able to spot the sign. If you have perfect color vision, you won’t be able to see it.

4. Classification design:
This is used to differentiate between red- and green-blind persons. The vanishing design is used on either side of the plate, one side for deutan defects an the other for protans.

Color blindness brings a lot of inconvenience to your work and life. The online color blindness test can help you test and evaluate whether you have color blindness and color weakness. If formal identification is required, please consult and see a doctor at the local ophthalmology department offline.

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