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

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.
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.
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.

Ishihara color test: The test most commonly used for diagnosis of red-green color defect. It utilizes colored numbers.
Anomaloscope is used for diagnosis of color anomaly.
Farnsworth Lantern Test: Developed for the US Navy.
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.
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.