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Colour blindness


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Colour blindness is the inability to differentiate between red, green or blue or a combination of these colours. It is also synonymous as colour vision problem (CVP).

What’s the science behind colour blindness?

The retina is made up of rods and cones. Cones are located in the centre of the retina or the macula, help in perceiving colour during daytime. There are three broad categories of cones- red, green and blue which provide eye’s colour sensitivity because they contain light sensitive pigments (trichromasy) within the visible spectrum. The biochemical process of colour perception is complex and a defect in the cones or absence of pigment leads to colour blindness of varied proportion.

Types of Colour Blindness and their symptoms

 Anomalous Trichromacy: Most common form of colour blindness in which one of the cone cells i.e. red, blue or green are altered. It’s of 3 types

  • Protanomaly: It is known as "red-weakness" i.e. absence of red cone cells. The individual faces difficulty in distinguishing red, orange, and yellow region of the spectrum
  • Deuteranomaly- Referred to as ”green weakness” or absence of green cone cells. They cannot perceive difference between red, orange, yellow, and green and blue-green.
  • Tritanomaly: It is a rare form of colour blindness characterized by decreased sensitivity of blue cones
Dichromasy- The individual is unable to recognize any two of these colours: blue, green or red or combination of colours. It’s of 3 types-
  • Protanopia: unable to spot red colour, difficulty to spot green, combination of blue and green appears gray
  • Deuteranopia: unable to spot green colour, cannot spot combination of red and green.
  • Tritanopia: absence of blue cone cells, cannot distinguish between yellow and blue colour
Monochromacy- is the rarest form of colour blindness, also known as complete colour blindness. It is marked by absence or 2 or 3 types of cone cells.


What causes colour blindness?

Colour blindness is mostly inherited. A baby can be born colour blind.
Acquired colour blindness can result from
  • Eye complications like macular degeneration, cataract, diabetic retinopathy, etc.
  • Injury or accidental damage of retina
  • Side effects of tuberculosis drugs, blood pressure medicines, nervous problems medicines, antibiotics, etc.
  • Exposure chemicals and gases like lead, carbon monoxide, etc.
  • People above 60 years might lose colour perception ability
How is colour blindness diagnosed?
Colour blindness could be detected in children and in adults during a comprehensive eye check up. The eye specialist conducts several colour vision tests to find out the type the individual is suffering from.
The most common test is the Ishihara 38 plate test which usually determines red and green colour blindness. The plates show you a pattern (number, alphabets or lines) made up of multi-coloured dots.  If you are colour blind then you will have a tough time finding the coloured dots.
The eye specialist will also ask you to undergo the colour arrangement test where you need to arrange the given colours in the predetermined order. The severity of colour blindness can be detected. 
Apart from that, your doctor will also check your medical history and examine your eyes for an underlying trauma or disorder.

Treatment for colour blindness
There’s no treatment for congenital colour blindness. You doctor may provide you special glasses that would help you to differentiate between colours.
Acquired form of colour blindness can be treated by addressing the problem- like altering the dose of medicine, eye surgery for cataract, preventing exposure of eyes to chemicals, etc.

There are several day-to-day strategies laid out at eye clinics for colour blind people. We suggest you to help your loved ones to understand them properly and ease their lifestyle.

Written by: healthplus24.com team
Date last updated: February 25, 2014