Physiological Integrity Q 35

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The client with color blindness will most likely have problems distinguishing which of the following colors?

  

     A. Orange

     B. Violet

     C. Red

     D. White

    

    

Correct Answer: B. Violet

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Clients with color blindness will most likely have problems distinguishing violets, blues, and green. The most common forms are protanopia and deuteranopia, conditions arising from loss of function of one of the cones, leading to dichromic vision. Protanopia is the loss of L cones (red) resulting in green-blue vision only. Deuteranopia is the loss of M cones (green) resulting in red-blue vision only.

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Option A: Color vision results from the combination of signals from three visual pigment types within cones: that of red, green, and blue, which correspond to cone types L, M, and S (RGB-LMS). Those colors correspond to the wavelengths of peak light absorption intensities of the modified chromophores. L cones have peak absorptions at 555 nm to 565 nm, M cones at 530 nm to 537 nm, and S cones at 415 nm to 430 nm.

Option C: Similar to above, but not as severe in its symptoms, is the condition anomalous trichromatic vision (tritanomaly), where all three cones are present but the color vision is aberrant. The two common forms, protanomaly, and deuteranomaly result in L or M cones, respectively, being replaced with a cone of intermediate spectral tuning. Both are X-linked and occur in 7% of males.

Option D: In addition to disorders of proper color recognition, many diseases in vision display phototransduction defects affecting many portions of the signal pathway and its regulation. Here, not only is color vision function lessened but scotopic (low-light, rod-associated) vision as well.

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