Colour Vision Testing
Colour vision is tested using Ishihara plates, named after Shinobu Ishihara a Japanese ophthalmologist who created a simple test to detect colour blindness in 1918. His test remains the gold standard worldwide.
Ishihara plates consist of numbers shaped out of dots of one colour superimposed on a circle of dots of another colour. In some cases the numbers disappear and appear or change. The full test has 38 plates, but most colour blindness can be detected by just four plates.