Color blindness: forms of the disease, diagnosis and risk factors

Colorblind people perceive colors differently from most people. Most of the time, this ophthalmological disorder makes it difficult to distinguish between certain colors.

What is color blindness and what causes it?

Color blindness is also known as “chromatic blindness”.

There are 2 types of cells responsible for our vision:

  1. Cone cells (color vision)
  2. Rod cells (contrast vision)

Color blindness occurs when certain photoreceptors in the cone cells of the eye do not exist, do not work properly or do not perceive certain colors.

There are 3 types of cone cells:

  1. L-cones: for seeing colors in the red spectrum and for long wavelengths
  2. M-cones for seeing colors in the green spectrum and for medium wavelengths
  3. S-cones: for seeing colors in the blue spectrum and for short wavelengths

The most common forms of color blindness are red-green. There are mild forms of color blindness (when photoreceptors are present but one type of cone cells does not function) or severe forms (when all 3 color photoreceptors are missing).

How many types of color blindness are there?

Depending on the time of occurrence, color blindness can be congenital or acquired.

  1. Congenital color blindness is caused by a genetic mutation and is inherited at birth.
  2. Acquired color blindness occurs throughout life, can affect one or both eyes, symmetrically or asymmetrically, is not constant and varies in intensity.

Risk factors for acquired color blindness:

Associated medical disorders:

  • Diabetes
  • Macular degeneration
  • Sickle cell anemia
  • Multiple sclerosis
  • Alzheimer’s disease
  • Parkinson’s disease
  • Leukemia
  • Optic nerve damage
  • Retinal diseases
  • injury to the eyes
  • Brain diseases
  • Metabolic diseases
  • Glaucoma
  • Cataract
  • Diabetic maculopathy
  • Sickle cell anemia

Medicines and substances

  • Hydroxychloroquine
  • Psychiatric medication
  • Treatment for tuberculosis
  • Drugs
  • Alcohol

Ageing increases the risk of acquired color blindness

Why are men more susceptible than women to color blindness?

The fact that color blindness is more common in men than women has to do with genetic structure and chromosomal inheritance.

The genes responsible for the development of color blindness are located on the X chromosome.

  • The situation for women: Women have two X chromosomes. For a woman to show symptoms of color blindness, the affected genes must be present on both X chromosomes. When they are only found on one of the chromosomes, the woman is a carrier but has no vision problems. However, she can pass on the affected genes to her children.
  • The situation in men: They have only one X chromosome. This means that if they get the affected genes from their mother, they will automatically get the disease.

How many forms of color blindness are there?

There are several forms of color blindness, depending on the photoreceptors affected. Most patients have problems with red-green color perception, but there are also forms that affect blue-yellow color vision.

Classification of forms of color blindness; Source: Verywell Health

Difficulty perceiving red-green colors

  • Deuteranopia
    • The colorblind person does not see green.
    • The colorblind people suffering from deuteranopia can identify up to 3 shades of green, compared to those with normal vision who can distinguish up to 7 shades of green.
    • There are rare situations in which deuteranopia is unilateral. This means that the disorder occurs in only one eye, while the other eye sees normally or has another color disorder.
  • Protanopia
    • The colorblind person does not see red.
    • Red is perceived as beige or grey.
    • This form of color blindness is rare, affecting only 1% of men.
  • Deuteranomaly
    • It’s a milder form than deuteranopia.
    • The colorblind person has difficulty perceiving the color green.
    • Shades of yellow and green are seen as shades of red.
  • Protanomaly
    • It’s a milder form than protanopia.
    • Colorblind people perceive red, orange and yellow as shades of green.

Difficulty perceiving blue-yellow colors

  • Tritanopia
    • It is one of the rarest forms of color blindness.
    • The colorblind person may mistake blue for green and yellow for violet.
    • Differentiating between blue and green, purple and red, yellow and pink becomes difficult.
    • Colors may appear less bright.
  • Tritanomaly
    • Tritanomaly is a milder form than tritanopia.
    • The colorblind person has difficulty distinguishing between blue and green, and yellow and red.

Black and white vision

  • Achromatism
    • It is one of the rarest forms of color blindness.
    • The colorblind person sees in shades of black and white because all the photoreceptors necessary for color perception are absent.

How is color blindness diagnosed? Color blindness tests.

Diagnosis of color disorders is made through specialized ophthalmological investigations, which include various tests for color perception. The most common are pseudoisochromatic tests, such as Ishihara or Stilling tests. These consist of plates with symbols drawn in circles of various colors, and help assess the patient’s ability to correctly identify those symbols.


Ishihara test; Source: All about vision

Other methods used in diagnosing color vision deficiencies include the color chip test, which involves assessing how certain colors influence perception. There is also the anomaloscope test, which provides detailed information about how the individual perceives and distinguishes colors.

An ophthalmological examination in one of Dr. Holhoș’ clinics will give you an accurate diagnosis. Using state-of-the-art medical technologies, specialists can identify the presence and severity of various forms of color blindness, providing solutions to improve the patient’s quality of life.

Is there a treatment for color blindness?

Currently, there is no definitive treatment for color blindness.

But there are a few ways in which the effects of this disorder can be reduced or corrected. Patients can use glasses with lenses recommended by their ophthalmologist, which change the spectrum of light and improve color perception. Furthermore, colorblind people can learn strategies to compensate for the absence of color perception by developing their own reference systems.

It is important to note that color blindness can influence career choices, limiting certain options. Affected individuals may have difficulty choosing careers such as electricians, pharmacists, surgeons or photographers, as these require accurate color perception. However, with the right support, many colorblind people can find fields in which they excel, making a significant contribution to society.

Text medically reviewed by Dr. Teodor Holhoș, Ophthalmic Surgeon
Written by Dr. Holhos Team

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