Anomaloscopes

An anomaloscope is an optical instrument used to diagnose and quantify color vision deficiencies. It operates by presenting the subject with a bipartite field, typically a circular disk divided into two halves. One half displays a fixed color, often yellow, and the other half is adjustable in its color mixture. The examiner adjusts the proportions of two primary colors, typically red and green, in the adjustable half until the observer perceives it as matching the fixed color. The specific ratio of red and green light required to match the yellow standard is then recorded.

The results from an anomaloscope test are often expressed as a ratio or a numerical value, which can indicate the severity and type of color vision defect. For instance, a normal color vision individual will require a specific, predictable ratio of red and green to match the yellow. Individuals with protanopia or deuteranopia, types of red-green color blindness, will require significantly different ratios or may be unable to achieve a match at all. Anomaloscopes are particularly useful in identifying the subtle variations in color perception that may not be apparent with simpler color vision tests. They are commonly used in clinical settings, occupational health assessments, and research related to color vision.