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Which test uses a screen illuminated with filters that have red on one side and green on the other?

  1. Pseudophakic test

  2. Duochrome test

  3. Color vision test

  4. Contrast sensitivity test

The correct answer is: Duochrome test

The Duochrome test is specifically designed to assess the patient's refractive error, particularly in distinguishing between myopia (nearsightedness) and hyperopia (farsightedness). This test employs a screen with red on one side and green on the other to help the patient determine which color appears clearer. The principle behind the Duochrome test is that a person with a refractive error will see one color more sharply than the other due to the chromatic aberration produced by the eye's lens. This characteristic of the Duochrome test makes it an effective tool in determining corrective lens needs, as it leverages the different focal lengths associated with the colors used. Thus, the use of contrasting colors on the screen is pivotal for evaluating visual acuity and refractive errors, validating its selection as the correct answer. Other options, such as the pseudophakic test, color vision test, and contrast sensitivity test, do not utilize this method of color comparison for assessing refractive error.