What test uses a screen that is half red and half green and is used during refinement?

The Duochrome test utilizes a screen that is typically half red and half green, making it specifically designed for assessing how well the eyes focus on different colors. During the refinement phase of a vision examination, practitioners often use this test to help determine the most suitable lens prescription for a patient. The contrasting colors assist in evaluating color perception and assessing refraction, particularly to identify any discrepancies in vision that may not be apparent with monochromatic stimuli.

In the context of this test, the way the eyes respond to the two colors can indicate whether the prescription needs adjustment and which color the patient can see more clearly with the optimal lens. This feedback is crucial in finalizing the lens prescription and ensuring the patient achieves the best possible vision correction.