Colour Blindness: Causes, Types, Symptoms & Treatment of Colour Blindness

Colour blindness or colour vision deficiency is a medical condition in which eyes lose the ability to distinguish between particular colours such as red, green and blue. It is a genetically inherited disorder caused chiefly due to alterations in single genes. 

The prevalence of colour blindness is observed more in males as compared to females. Deuteranopia, protanopia, and tritanopia are the three types of colour vision deficiency which we have covered in more detail in this article along with their causes, symptoms and treatment. 

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What is Colour Blindness?

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Colour blindness or colour vision deficiency is defined as a mendelian disorder in which a person finds trouble seeing or identifying colours like blue, green, yellow, and red. It was first identified an english chemist, John Dalton in 1798. Later, after the discovery of disease, colour blindness disease was also regarded as Daltonism. John Dalton also explained that the person with the family history of colour blindness are more likely to be affected by this disease. 

• Colour vision deficiency is inherited from biological parents, and usually, males are more susceptible to this disease.
• A colour blind person may also find difficulties in differentiating the spectrum of shades of colours. 
• This disease is caused when the nerve cells on the retina do not function properly. 
• Other reasons for colour blindness can be eye disorders and consumption of certain drugs. 

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Types of Colour Blindness

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The types of colour blindness depends on the absorption of light by cones (nerve cells). Three types of cones namely blue, green and red are present. In this section, we will discuss the types of colour vision problems in detail. 

Different Types of Colour Blindness

Red-Green Colourblindess

One of the most common types of colour vision problems is the red-green colourblindness which is also called deuteranopia and protanopia. The damage of the red or green cone pigment present in the retina of the eye results in this disease. Individuals with this problem are unable to identify blue, green, orange, red, and purple shades.

Blue-Yellow Colourblindness

This is one of the rarest types of colour blindness that affects both males and females. Blue-Yellow colour blindness are often called tritanopia. People suffering from tritanopia could not differentiate between yellow and red and between blue and green shades. Individuals with blue-yellow colour blindness have non-functional blue cones.

Complete Colourblindness

Complete colourblindness is a serious condition where a person does not see colour at all. A person with this disease sees all colours in shades of grey, black and white. Either two or all three cones are absent in this case. Cure of this type of colour blindness is next to impossible. 

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Causes of Colour Vision Deficiency

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The healthy retina of the human eye contains two light-sensitive cells which are the rod cells and the cone cells. The rod cells are responsible for low light vision, whereas the cone cells are responsible for normal, bright light and coloured vision. Colour blindness is affected when any of these two light-sensitive cells fail to perform their specific functions. Apart from this, several other factors are also responsible for causing colour vision deficiency in any individual such as: 

• Eye injuries caused by laser treatments
• Genetic disorders and cell mutations.
• Side effects of drug addiction.
• Use of narcotics like tobacco and alcohol.
• Tumors in the brain.
• Radiation therapies.

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Symptoms of Colour Blindness

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One of the major symptoms of colour blindness is the incapability of not seeing colours as the majority of people do. A few symptoms are mentioned below:

• Rapid and continuous eye movement.
• Sensitivity towards bright light.
• Trouble in seeing different colours like red and green, blue and yellow.
• Not able to see the brightness of any colour.
• Exposure to chemicals in industries.

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Diagnosis of Colour Blindness

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Diagnosis of colour blindness can be carried out using various colour vision tests. Doctors usually prefer the Ishihara Plate test for diagnosis.

Ishihara Plate Test

This type of test is conducted to diagnose patients with red-green deficiency. In this test, about 38 plates are used in which irregular coloured dots are present that form numbers. During this colour vision test, patients are asked to identify the specific number present on the plate.

Ishihara Plate Test

Hardy, Rand, Rittlers Test

Hardy, Rand, and Rittlers Test also called HRR colour vision test, is similar to ishihara plate test. The only difference between the two is that the Ishihara test diagnoses red-green colour deficiency, while all HRR test is used in the diagnosis of both blue-yellow and re-green colour deficiency.

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Treatment of Colour Blindness

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Currently, there is no specific treatment for colour blindness but various photographic filters and eyeglasses are used to improve the vision to some extent. 

• Enchroma glasses are used by people with red-green colour deficiency.
• Depending on the intensity of colour blindness colour-corrective lenses are put into use.
• Some software and applications like Colour Blind Pal are used. 

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Things to Remember

• The photoreceptor cells on the retina called cones, are responsible for providing vision.
• Colour blindness is an inherited disease caused by mutation in genes.
• There are two types of colour vision deficiencies: blue-yellow and red-green.
• People with blue-yellow colour blindness visualize blue and yellow colours as grey or green. 
• Pseudoisochromatic colour plates are used in the Ishihara plate test.

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Previous Years Questions

•  Which of the following is an example of pleiotropy ?…..[ CUCET 2011]
• Who proposed the chromosomal theory of inheritance ?….[CUCET 2010]
• The children of a father with type 'O' blood and mother with type….[COMEDK UGET 2012]
• Epicanthus skin fold above the eyes and transverse palmer….[COMEDK UGET 2007]
• Distance between the genes and percentage of….[COMEDK UGET 2015]
• Which one of the following is a sex-linked disease….​[CUCET 2010]
• The science that deals with the application of principles….[CUCET 2010]
• A 10 years old patient is found to have the following….[COMEDK UGET 2012]
• Which of the following genes shows the heterozygous...[BHU UET 2008]
• Which chromosomal constitution refers to Jacob's syndrome….[BHU UET 2012]
• Which of the following is an example of intergenic gene….
• Which of the following is not considered as a mutagen…
• Haemophilia is an example of….
• In order to lessen the suffering of phenylketonurics...[AMUEEE 2014]
• In Mendel's experiments with garden pea, round seed shape..[JKCET 2015]
• Genotypic and phenotypic ratio in monohybrid cross remains..[JKCET 2011]