Which test uses a screen that is half red and half green?

The test that uses a screen that is half red and half green is known as the duochrome test. This examination is designed to assess a person's refractive error by determining their ability to distinguish between red and green hues under specific lighting conditions.

During the test, the participant views the two colored halves of the screen, each presenting a different visual stimulus. The individual is asked to indicate which color appears clearer. This process helps the examiner establish whether the patient is over- or under-corrected in their prescription by evaluating their responses to the contrasting colors.

The duochrome test is particularly effective because it capitalizes on the way the human eye perceives colors differently due to the optical properties of the eye, thereby revealing important information about visual acuity and the need for corrective lenses. The design of the test, using distinct red and green segments, provides a straightforward method for practitioners to pinpoint refractive issues.