Color Blindness: Signs, Causes & Treatment!

Color blindness or color vision deficiency is a disorder in which there is a decreased ability to spot colour differences & recognize colors.


  • Inability to properly separate & limited variability in the red-green color axis.
  • For eg: People with dichromacy have difficulty in distinguishing a green apple from a red apple & from a red traffic light with the green traffic light.
  • Inability to distinguish between red/amber traffic lights & yellow street lamps.
  • In total color blindness, there is a total inability to distinguish between colors & hence everything is seen as either black or white.
  • Light sensitivity
  • Involuntary movement of the muscles of the eye.
  • Nearsightedness.
  • Poor vision.


Inherited disease/Genetic factors: Color blindness occurs due to a mutation in the X chromosome.

Some of the inherited diseases are:

  • Cone dystrophy
  • Cone-rod dystrophy
  • Achromatopsia (also called rod monochromatism)
  • Blue cone monochromatism (also called blue cone monochromacy)
  • Leber’s congenital amaurosis
  • Retinitis pigmentosa (initially affects rods but can later progress to cones and therefore color blindness).

Classification on the basis of color deficiencies & mechanism

  1. Monochromatic: Total color blindness caused to to damage & absence of cone cells.
    a) Rod monochromacy: Result of non-functioning retinal cones.
    b) Cone monochromacy: Damage of more than one cone in the retina or presence of more than one type of dichromatic color blindness.
  2. Dichromatic
    a) Protanopia: Caused due to complete loss of red retinal receptors.
    b) Deuteranopia: Presents an additional dimming effect along with the preceding symptoms of protanopia.
    c) Tritanopia: Total absence of blue retinal receptors.
  3. Anomalous trichromacy: One of the three cone pigments is altered in the spectral sensitivity.
    a) Protanomaly: Altered sensitivity of red retinal receptors & variability in the red-green hue.
    b) Deuteranomaly: Altered sensitivity of green retinal receptors & mild variability in the red-green hue.
    c) Tritanomaly: Affecting blue-green & red-yellow hue.

Acquired Causes/Other Risk factors:

  • Drug/chemical mediated:
    a) Hydroxylchloroquin, used for malaria
    b) Ethambutol, used for treatment of TB
    c) Styrene
    d) Organic solvents
  • Disease/Disorder related:
    a) Trauma
    b) Swelling of the occipital lobe
    c) Damage to the retina due to exposure to UV radiation.
    d) Age related degeneration
    e) Diabetes
    f) Vitamin A deficiency
    g) Chronic solvent-induced encephalopathy (CSE), caused by long-time exposure to solvent vapors.


  1. Ishihara color test: The test most commonly used for diagnosis of red-green color defect. It utilizes colored numbers.
  2. Anomaloscope is used for diagnosis of color anomaly.
  3. Farnsworth Lantern Test: Developed for the US Navy.
  4. Farnsworth–Munsell 100 hue test, used to measure chromatic discrimination, therefore the patient is asked to arrange a set of colored caps or chips to form a gradual transition of color between two anchor caps.
  5. HRR color test is a green-red color test.


There are no treatments currently for color blindness:

  • Drug acquired color blindness may subside after stopping of the use of the drugs responsible.
  • Treatment & management of disorders may or may not prevent color blindness.
  • The most common form pf management is use of colored spectacle lenses or use of wavelength lenses, which may help in identifying some colors.
  • Many mobile and computer applications have been developed to help color blind individual to view better/differentiate between colors.


  • Labeling of essential material & objects.
  • Putting stuff in a particular order that can be easily memorized.
  • In certain countries like Canada, UK, Netherlands, traffic signals/lights are aligned in a horizontal fashion with every light (Red, yellow, Green) is a different shape.