anomaloskop

An anomaloskop, also known as an anomaloscope, is an optical instrument used to assess human color vision by performing precise color-matching tests. It is especially employed to diagnose and quantify red–green color vision deficiencies and to distinguish among normal trichromacy, anomalous trichromacy, and dichromacy.

The device presents two fields of light to the eye. In a common Rayleigh-type anomaloscope, one field provides a fixed reference light (often a yellow-green spectral composition around 589 nm), while the other field is a mixture of two wavelengths (typically red and green) whose relative luminance can be adjusted. The observer adjusts the test-field mixture until the two fields appear identical in color and brightness. The resulting settings are compared with normative data to determine the type and degree of color vision deficiency.

There are several designs, with the Nagel and Rayleigh configurations being among the most widely used. The Nagel setup emphasizes a fixed reference and an adjustable field that the patient matches through color mixing, whereas other variants may differ in reference wavelengths or luminance control. Interpretation focuses on whether a normal match can be achieved and, if so, at what balance of components; anomalous observers show characteristic shifts or ranges that indicate deuteranomaly, protanomaly, or other color vision anomalies.

Applications of the anomaloscope include clinical color-vision testing, occupational screening, and research on color perception. It is considered a robust, quantitative test for red–green deficiencies but is less informative about blue–yellow deficiencies. Proper use requires standardized lighting, trained examiners, and interpretation against established reference data.