An anomaloscope is an instrument used to test for CVD and is considered the gold standard to which other tests are compared.

The apparatus was invented by the German ophthalmologist and physiologist Willibald A. Nagel (1870–1911) who named it “Anomaloskop” in 1907. Nagel’s Anomaloscope utilized a Raleigh Match, where red + green are compared to yellow, which is appropriate for accessing red-green color defects. To assess blue-yellow defects, a different anomaloscope must be used that utilizes the Moreland Match and compares blue + green to cyan.

Despite being the gold standard, anomaloscopes are very expensive and can only be operated and interpreted by color vision experts. For these reasons, it is much less commonly used than Pseudoisochromatic Plates, Lanterns or Arrangement Tests.

Modern Anomaloscope