Ishihara Color Test for Color Blindness
The Ishihara Color test is a test to determine if a patient has color blindness. It was named after Dr. Shinobu Ishihara who first published the test in 1917 as a professor at the University of Tokyo.
The test is made up of a series of circles comprising many small colored dots, called Ishihara Plates. Certain colored dots within each circle combine to form a number or pattern – the ability to correctly determine the number or pattern reveals whether or not a person may be color blind.
While the full test contains 38 plates, our test comprises the first 24 plates and will give you an accurate idea of the severity of your color blindness. This test is designed to identify the most common form of color blindness – red green color blindness.
Color Arrangement Test for Color Blindness
The Farnsworth arrangement test, or more commonly – the color arrangement test, was originally developed for Navy use by Commander Dean Farnsworth in 1943 at the Naval Laboratory. Based on the combined work of Farnsworth and Deane Judd (1943-1945), in 1947 the Farnsworth Dichotomous Test (D-15) was created. The D-15 test was designed to distinguish the differences in visual ability between color blind or color deficient people, and those with normal color vision.
The test above is a simulation by Daniel Flück (colblindor.com) of the D-15 test originally created by Farnsworth. The test results are based around the lines of confusion. These lines are associated with Protan (red), Deutan (green), and Tritan (blue) color blindness. Using a mathematical formula developed by Vingrys and King-Smith in 1988 to derive your personal color difference vector, a line can be drawn and its angle compared to the three confusion lines. This makes it possible to quantify the type and severity of your color blindness.
The following table shows the average results of a test of 120 normal and color blind people as published in the original Vingrys and King-Smith paper:
To help understand this data, refer between the following explanations and the figures above:
- Angle: The confusion angle is used to identify which type of color blindness you have. You can use the above table to see where your color blindness fits in.
- Major and Minor: The ratio of the major and minor radius gives the S-index.
- TES: The major and minor radius are combined to give a total error score, this measurement is used to determine the severity of your color blindness. The results range from about 11 for normal vision, to 40 and above for severe color deficiencies.
- S-Index: The selectivity index represents the parallelism of the confusion vectors to your personal confusion angle. Scores of 2 or less suggest little to no color blindness, scores above 6 indicate high parallelism.
- C-Index: The confusion index is the ratio between your major radius and the major radius of a perfect arrangement. Perfect color vision has a C-Index of 1, whereas color blind people will score between 1 and 4 (sometimes higher). The higher the number the more severe your color blindness.