The duochrome test is a visual acuity test that helps evaluate and correct refractive errors in vision. The test uses two colors, usually red and green, that appear superimposed on top of one another. The patient is asked to identify which color is clearer or sharper, which helps determine whether the patient is nearsighted or farsighted. Synonyms for the duochrome test include the red-green test, the bichrome test, and the dichromatic test. While all of these terms refer to the same basic test, some eye care professionals may prefer one term over another. Regardless of the term used, the duochrome test plays an important role in identifying and correcting vision problems.