IshiharaTest

The Ishihara test, also known as the Ishihara color vision test, is a widely used screening tool for color vision deficiency. It was developed by Japanese ophthalmologist Shinobu Ishihara in 1917. The test uses pseudoisochromatic plates—arrays of colored dots arranged to form numerals or shapes—that are typically visible to people with normal color vision but may appear differently or be indistinguishable to those with red-green color deficiencies.

In its standard format, the plates are presented under standardized illumination, and respondents are asked to identify the number or pattern seen in each plate. A typical result shows a consistent set of responses among individuals with normal color vision, while those with red-green deficiencies may see different digits or fail to perceive the figure. The most widely used version consists of 38 plates, though shorter editions (for example, 24-plate tests) are also used for quicker screening.

Interpretation of results provides an indication of the presence and, in many cases, the type of red-green deficiency (protan or deutan). However, precise typing and assessment of severity often require additional testing with other color vision tests. The Ishihara plate test is primarily a screening instrument and not a full diagnostic evaluation.

Limitations include limited sensitivity to blue-yellow deficiencies, potential influence from lighting conditions, age, ocular media opacities, or medication effects, and the fact that it does not quantify the degree of deficiency. It may also misclassify some individuals, particularly those with mild color vision anomalies.

Usage spans ophthalmology clinics, schools, and occupational health screenings worldwide. It is commonly employed as an initial color vision assessment and is often part of a broader battery of tests.