Anomaloscope

The anomaloscope contains a red-green scale from which may be read a number that is proportional to the amount of red in the mixture field, and a Y scale from which is read a number proportional to the luminance of the test color. In testing an observer, the examiner notes the scale values, which then are available for further transformation as noted for the Nagel anomaloscope.

For the differentiation between color vision defects of retinal origin and color defects as a result of optic nerve disease the determination of the neutral zone and anomaloscope examination are important.

Anomaloscopes are instruments that assess the ability to make metametric matches. The results are used for definitive diagnosis and quantitative assessment of color vision status. Anomoloscopes are much more difficult to administer than pseudoisochromatic plates and arrangement tests. The first anomaloscope was designed by Nagel and is based on the color match known as the Rayleigh equation, that is, R + G = Y.