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All About Colour Blindness

Colour vision problems are typically innate conditions which can impair the ability to distinguish between colour tones. Many are not aware that this condition does on occasion develop later in life. The human eye contains receptor cells known as rods and cones.  Colour blindness is a result of a dysfunction of the cones in the retina, commonly impairing a viewer’s ability to differentiate between varieties of red or green, but it could influence the ability to see additional hues as well.

.  Rods detect illumination, while the role of the cones is to differentiate colours. People are normally born with three varieties of cones, each of which perceive different wavelengths of colour. Different wavelengths of light are perceived as different colours. Short wavelengths of light are seen as blues, medium wavelengths of light are seen as  greensand longer wavelengths of light are seen as reds.

Because it is a genetically recessive trait located on the X chromosome, colour blindness is more common in males than in females. A female with the colour blind trait on only one X chromosome will have normal colour vision, but will be a carrier of the colour blind gene, and may pass on the colour blind trait to her children.  Although uncommon, there are some females who do suffer varying degrees of colour blindness. Some people acquire colour blindness later in life as a result of other conditions such as macular degeneration, neurological disease and medicinal side effects. More and more, new computer applications are becoming available for standard PCs and even for mobile machines that can assist users to distinguish colour better depending upon their specific diagnosis. There is also exciting research underway in gene therapy that may improve colour vision.

The extent to which colour blindness limits a person depends on the type and severity of the deficiency. Some are not able to perceive reddish colours and others have problems with blue hues. Some are affected by their capacity to see multiple colour spectrums.  Normal colour vision is important for some occupations.   Police officers, pilots, electricians and artists are some examples.

Eye doctors use a variety of tests to diagnose these colour vision disorders. The most widely used is the Ishihara colour exam, called after its inventor. For this test a patient views a plate with a group of dots in a circle in seemingly random sizes and colours. Within the circle, one with normal colour vision can see a digit in a particular colour. The individual’s capability to make out the number within the dots of clashing hues indicates the level of red-green colour blindness.

Without corrective measures, some patients can adapt to their deficiency by familiarizing themselves with alternative cues for coloured objects or signs. For example, learning the shapes of stop signs (instead of recognizing red) or contrasting objects with reference objects like green grass or a blue body of water can help.

If you suspect that you or a loved one might have a colour vision deficiency it’s important to schedule an appointment with an optometrist. The sooner the condition is diagnosed, the easier it will be to manage. Feel free to call our Mississauga, ON eye care practice for information about scheduling an exam.