Name the common human color vision deficiencies and the cone photopigment affected.

• A. Protanopia (L-cone), Deuteranopia (M-cone), Tritanopia (S-cone)
• B. Myopia with colorblindness
• C. Hyperopia and color blindness
• D. Trichromacy deficiency

Answer: (A)

Color vision deficiencies arise from loss or dysfunction of one of the retina’s three cone pigments: L (long, red), M (medium, green), and S (short, blue). The common patterns are protanopia, where the L-cone pigment is absent; deuteranopia, where the M-cone pigment is absent; and tritanopia, where the S-cone pigment is absent. Protanopia and deuteranopia mainly disrupt red-green discrimination, while tritanopia disrupts blue-yellow discrimination. These deficiencies are defined by which cone pigment is affected, which is exactly what this option lists. The other choices mix color vision with refractive errors or suggest a nonstandard “trichromacy deficiency,” which isn’t how these conditions are described.