Ishihara Test

A widely used clinical screening test for red-green colour vision deficiencies, consisting of a series of circular plates made up of coloured dots arranged in a mosaic pattern. Each plate contains a number or shape formed by dots of certain colours set against a background of dots in confusing colours. People with typical colour vision can identify the embedded figure, while people with specific colour vision deficiencies cannot distinguish the figure from the background. Developed by Japanese ophthalmologist Shinobu Ishihara in 1917, the test primarily detects protanopia and deuteranopia but not tritanopia. The Ishihara test is frequently used in accessibility research to verify and classify participants' colour vision status.