Colour blindness or CVD (Colour vision Deficiency) is the inability to fully see certain colours. This happens when the colour recognizing receptors in the eyes fails to work properly.

There are different types of colour blindness with the most common form being red/green colour blindness. The person suffering from this type will be unable to see the red and green elements in any colour. For instance, these people will not be able to distinguish between the colours purple and blue as they won’t be able to see the red element in purple. They will see both colours as blue.

Causes & Risk Factors

Heredity is the single most important factor in deciding whether a person becomes colour blind or not.This particular trait is carried by the X chromosomes. The male gene has a single X chromosome while the female gene has two X chromosomes. This makes males more vulnerable to colour blindness than females, who can be colour blind only if a woman has a carrier mother and a colour deficient father.

However, certain conditions such as glaucoma, Alzheimer’s disease, macular degeneration, chronic alcoholism, sickle cell anaemia, Parkinson’s disease and leukaemiaand the usage of certain drugs such as hydroxychloroquine (used to treat Rheumatoid Arthritis) can increase the chances of acquiring colour blindness.

Accidents and head injuries causing permanent damage to eyes can also be a cause for colour blindness. Another reason can be the exposure to UV rays.


Signs or symptoms of colour blindness in children can be noticed by parents or teachers in most cases. However, in a lot of cases, it manifests ever so slightly that it will hardly be noticed.

Symptoms can include:

  1. Difficulty in distinguishing between colours,
  2. Inability to distinguish different tones or shades of the same colour
  3. Sensitivity to bright light
  4. Excellent sense of smell and night vision
  5. Children might be disinterested in colouring worksheets, playing with coloured blocks, etc
  6. Rapid eye movements may occur in severe cases


Eye specialists usually check for colour blindness while running the regular eye exam.Common ways of testing the condition include the Ishihara Colour Test and Hardy-Rand-Rittler (H-R-R). In these tests, the subject is asked to identify coloured numbers or shapes that lie among dots of varying colours and intensity. The physician determines the intensity and category of the condition according to the responses by the subject.


Unfortunately there is no treatment for colour blindness yet. However, some measures can be taken to compensate for it such as the use of certain tinted or coloured glasses and lenses. Most colour blind people have an otherwise normal vision, and therefore some minor adjustments or adaptations make it easy for them to cope with the condition.

Preventive measures

Colour vision deficiency, if inherited cannot be prevented. Avoiding head injuries and checking the side effects of medicinal drugs can prevent colour deficiency due to causes that are not linked to genes.

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