The Ishihara Test

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While discussing ‘Colour Blindness’ before the SC [Pranay Poddar v. State of Tripura, Civil Appeal No. 4393 of 2017], Senior Advocate K.V. Vishwanathan quoted Shinobu Ishihara, a Professor at Tokyo Imperial University who, in the year 1916, had developed a diagnostic method which is still the most common test for ‘Colour Vision Deficiency’; and that test is called Ishihara Test.

The test consists of a number of coloured plates, called Ishihara Plates, each of which contains a circle of dots appearing randomized in colour and size. Within the pattern are dots which form a number or shape clearly visible to those with normal colour vision, and invisible, or difficult to see, to those with a red-green colour vision defect, or the other way around. The full test consists of 38 plates, but the existence of a deficiency is usually clear after a few plates.

Ishihara Plate No. 1
Ishihara Plate No. 1

Though many methods for color vision testing are available there is no consensus on the ideal method, with different countries using different tests. In India, the Ishihara Charts are the most widely used, with additional use of Edridge-Green Lantern in Civil Services.

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Edridge-Green

The Eldridge-Green Lantern Test, 1891 was used by the U.S. Navy for qualification of midshipmen and line officers prior to adoption of the Farnsworth Lantern Test (FALANT) in 1953. FALANT is the final qualifying test for the U.S. Navy, the U.S. Coast Guard Academy, and the U.S. Merchant Marine Academy.

One might remember Professor Hubert J. Farnsworth from Futurama, an American animated science fiction sitcom [IMDb 8.5/10; TV.com 9.1/10].

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Professor Farnsworth

In ‘All the Presidents’ Heads’ [23rd episode, 6th Season] he reveals that he has descended from Dean Farnsworth, the creator of FALANT.

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