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Colour Blindness

What is Colour Blindness?

Colour blindness occurs when cones (the light sensors in the retina that respond to colour) are formed with an incorrect balance of the pigments necessary to see colour. Someone who is colour blind cannot distinguish between certain colours.

There are three colour sensitive cones in the retina which respond to red, green and blue light. Combinations of these three colours allows us to appreciate all of the colours of the rainbow. Loss of just one of these cones will disrupt the colour vision and loss of two of these cones will reduce images to black and white.

Causes of Colour Blindness

Colour deficient vision is either inherited, or as a side-effect of an illness or medication.

Inherited Colour Blindness

Inherited colour deficient vision is more common. Red, green and blue colour deficiency is carried in the genes, and the majority of affected individuals are males. A recessive gene in both males and females carries total colour blindness. Inherited colour deficiency can vary from mild to severe, but will not worsen over a lifetime.

Colour Blindness in later life

Changes can occur due to diseases which affect the eye or brain or through excessive use of medication. Poor blue vision is the most common colour abnormality later in life.

Diagnosis of Colour Blindness

A number of tests have been produced to test for colour blindness. Most require the recognition of a coloured symbol or figure carefully constructed to be confused with the background

Treatment for Colour Blindness

Coloured filters in the form of spectacles or contact lenses for colour deficient people can improve performance on colour vision testing but often have limited benefit in daily living.

Acquired colour vision loss can occasionally be reversible depending on the cause eg, stopping medications such as chloroquine or ethambutol.

Eye surgery may sometimes help to improve colour perception for example cataract extraction, retinal detachment repair and the prevention of further deterioration in colour vision. Retinal laser treatment of diseases affecting the back of the eye eg, diabetic maculopathy, age related macular degeneration can occasionally reverse acquired colour loss.