• The figure is used as an initial screening for the most common color vision anomalies, such as color blindness, where one cannot distinguish between red and green (deuteranopia).
  • The tested person should be able to name the colors.
  • The duochrome red-green test is also a standard tool for determining the eye’s refractive point (refraction).
  • When looking at the red/green chart, the patient is asked: “Which is clearer, the letters on the red side or the letters on the green side?” If the answer is green, additional minus power (-) is needed.
  • If the answer is red, additional plus power (+) is required.
  • This is usually done with one eye at a time, and then with both eyes together.
  • The premise of this test is that green wavelengths of light focus in front of the retina, while red wavelengths focus behind the retina.

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