Ishihara Color Blindness Test
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.
The Ishihara color blindness test is one of the most common color blind tests in the world. Ishihara test mainly detects red-green color blindness.
There are 38 plates in the Ishihara blind test, where each plate contains dots of different sizes and colors. All dots on plates are arranged in specific patterns to form numbers or figures that people with normal color vision can see.
People with color deficiency won't be able to see the numbers of figures on these colored plates. Some of the Ishihara plates are visible only to the people suffering from color vision deficiency, and there are invisible to those with normal color vision.
The standard Ishihara test has 36 colored plates, but there is more Ishihara test with 10, 14 or 24 plates.
Types of colored plates in Ishihara test
The demonstration plate is the first plate in the Ishihara test with the number "12" and can be "16". This demonstration plate is seen by all individuals having normal color vision or deficient color vision. It is only used for demonstration purposes and not considered in making a score for screening purposes.
People with normal color vision can distinguish different figures or numbers from people suffering from color vision defects.
Only people with normal color vision can see vanishing plates. i.e., Figures or numbers on the plates can ot seen by color vision defective people.
Hidden digit plates
Figures and numbers on these plates can be seen only by people with color vision defects.
These plates help diagnose the type of color vision defect protanopia (red deficiency) or deuteranopia (green deficiency) and its severity.