The Ishihara test is a color perception test for red-green color deficiencies the first in a class of successful color vision tests called pseudo-isochromatic plates. It was named after its designer Dr. Shinobu Ishihara a professor at the University of Tokyo who first published his tests in 1917.

The test consists of a number of colored plates called Ishihara plates each of which contains a circle of dots appearing randomized in color and size. Within the pattern are dots which form a number or shape clearly visible to those with normal color vision and invisible or difficult to see to those with a red-green color vision defect. Other plates are intentionally designed to reveal numbers only to those with a red/green color vision deficiency and be invisible to those with normal red/green color vision. The full test consists of 38 plates but the existence of a severe deficiency is usually apparent after only a few plates. There is also an Ishihara test consisting 10 14 or 24 test plates.

The plates make up several different test designs:
* Demonstration plate (plate number one typically the numeral "12"); designed to be visible by all persons whether normal or color vision deficient. For demonstration purposes only and usually not considered in making a score for screening purposes.
* Transformation plates: individuals with color vision defect should see a different figure from individuals with normal color vision.
* Vanishing plates: only individuals with normal color vision could recognize the figure.
* Hidden digit plates: only individuals with color vision defect could recognize the figure.
* Diagnostic plates: intended to determine the type of color vision defect (protanopia or deuteranopia) and the severity of it.