What does the red/green test actually do?

The Duochrome (Red/Green) test is one of the methods your Optometrist may use when refining your glasses prescription. This test uses the eye’s attribute of how it focuses light of differing colours.

Red and green light rays don’t fall in exactly the same place on the back of your eye due to something called chromatic aberration. Green rays should fall very slightly in front and red rays should fall very slightly behind the retina if your glasses prescription is correct. If your prescription is slightly too strong or slightly too weak, the circles can stand out or look “blacker” on one of the coloured backgrounds.

As with all the subjective tests at our disposal don’t worry if you feel you struggle with this particular one as there are other tests that we can utilise to accurately determine your prescription.