You searched for: “leukoscopes
leukoscope, leucoscope (s) (noun); leukoscopes; leucoscopes (pl)
An instrument devised for testing the color perception of the eyes: A leukoscope can be use for comparing different lights as to their constituent colors or their relative whiteness.

A leukoscope is a tool for testing the eyes to determine the ability to distinguish variations in colors or the intensity of lights.