Vision

Color Blindness

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Color Blindness, Color Blind, Color Vision Deficiency, Blue-Yellow Color Blindness, Blue-Yellow Dyschromatopsia, Tritanomaly, Tritanopia, Tritan defect, Red-Green Color Blindness, Red-Green Dyschromatopsia, Deuteranomaly, Deuteranopia, Deutan defect, Red Color Blindness, Protanopia, Protanomaly, Protan Defect, Blue Cone Monochromacy, Achromatopsia, Monochromacy

  • See Also
  1. Retina
  • Pathophysiology
  1. Each of three cone types contains a specific opsin photopigment, and each is encoded by a specific gene
    1. L-Cones (long wave length cones, yellow-orange, OPN1LW gene)
    2. M-Cones (middle wave length cones, yellow-green, OPN1MW gene)
    3. S-Cones (short wave length cones, blue-violet, OPN1SW gene)
  2. Genetic Defects
    1. Red Green Color Blindness
      1. Genetic defect of OPN1LW or OPN1MW
      2. Abnormal opsin pigments or absent L-Cones or M-Cones
    2. Blue-Yellow Color Blindness
      1. Genetic defect of OPN1SW
      2. Defective S-Cones or premature destruction of S-Cones
    3. Complete Color Blindness (Blue Cone Monochromacy)
      1. Genetic defect in both OPN1LW and OPN1MW
      2. Defective L-Cones and M-Cones, leaving only functional S-Cones
  3. Acquired Defects
    1. Glaucoma
    2. Retinitis Pigmentosa
    3. Vitamin A Deficiency
    4. Alcoholism
    5. Toluene Poisoning
    6. Medications (e.g. Ethambutol, Phenytoin, Phosphodiesterase Inhibitor)
  • Types
  1. Red-Green Color Blindness
    1. Most common Color Blindness types
    2. Far more common in males (X-Linked)
      1. Males (1 in 12 of northern european descent)
      2. Females (1 in 200 of northern european descent)
    3. Difficulty distinguishing between red and green
    4. M-Cone Disorders (related to green Perception)
      1. Deuteranomaly (most common, dysfunctional M-Cones)
        1. Green appears similar to red (mild dysfunction)
      2. Deuteranopia (loss of M-Cones)
        1. Unable to differentiate green and blue (severe dysfunction)
        2. Results in dichromic Vision (red-blue Vision only)
    5. L-Cone Disorders (related to red Perception)
      1. Protanomaly (dysfunctional L-Cones)
        1. Red appears similar to green, and more dull (mild dysfunction)
      2. Protanopia (loss of L-Cones)
        1. Unable to differentiate green and blue (severe dysfunction)
        2. Results in dichromic Vision (green-blue Vision only)
  2. Blue-Yellow Color Blindness (Tritan defects)
    1. Less common Color Blindness types (<1 in 10,000 persons worldwide)
    2. Difficulty distinguishing between blue and green as well as blue and black
    3. S-Cone Disorders (related to blue Perception)
      1. Tritanomaly (dysfunctional S-Cones)
        1. Difficulty distinguishing between blue and green
        2. Difficulty distinguishing between yellow and red
      2. Tritanopia (loss of S-Cones)
        1. Difficulty distinguishing between blue and green
        2. Difficulty distinguishing between purple and red
        3. Difficulty distinguishing between yellow and pink
        4. Colors appear dull
  3. Complete Color Blindness (Blue Cone Monochromacy, Achromatopsia)
    1. Rare (<1 in 100,000 persons worldwide)
    2. Autosomal Recessive genetic disorder
    3. Results in severe reduction in color Vision and poor Visual Acuity
    4. May also be associated with photophobia, Nystagmus and Myopia
  • Diagnosis
  1. Color Vision Test (e.g. Ishihara Color Test)
  • Management
  1. Treat underlying causes in acquired Color Blindness
  2. Eyeglass or Contact Lens colored filters may enhance color contrast and differentiation
  • Resources
  1. Color Blindness (NIH, for patients)
    1. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/color-blindness/types-color-blindness
  2. Color Vision Deficiency (Medline Plus)
    1. https://medlineplus.gov/genetics/condition/color-vision-deficiency
  • References
  1. Naifeh (2021) Color Vision, Stat Pearls, accessed 12/13/2021
    1. https://www.ncbi.nlm.nih.gov/books/NBK470227/