Which color vision defect is best described as a red weakness?

• A. Protanomalous
• B. Deutanomalous
• C. Tritanomalous
• D. Achromatopsia

Answer: (A)

The red-weakness is due to an abnormality in the long-wavelength (red) cone pigment. Protanomalous is a mild anomaly of these red cones, shifting their peak sensitivity and making red colors appear less saturated or more similar to greens. This is why reds can look partially greenish or harder to distinguish from greens, especially in certain lighting. It’s a red-green color deficiency, but milder than a complete loss of red perception. In contrast, a green-weakness affects the green (M) cones, blue-yellow issues involve the blue (S) cones, and achromatopsia is complete color blindness. So protanomalous best fits a red weakness.