Why is color vision testing more effective if performed monocularly?

• A. Acquired color vision defects are often monocular.
• B. Binocular cues improve color vision accuracy.
• C. Color vision testing is fastest with both eyes.
• D. Monocular testing is not possible for color vision.

Answer: (A)

Color vision testing is most informative when done monocularly because many acquired defects affect one eye more than the other. Testing each eye separately isolates what that eye perceives, making unilateral color problems detectable. If both eyes are tested together, the normal eye can compensate or mask a defect in the other eye, potentially hiding an issue. Congenital color vision defects, by contrast, are usually bilateral, so monocular testing helps distinguish unilateral acquired problems from lifelong, symmetrical deficits.