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Are You Colour Blind?

What’s it like to be colour blind? You may not know you have colour blindness because many people are born with this condition and have no comparison to normal colour vision.  Contrary to what the name implies, colour blindness usually does not actually mean that you don’t see any colour, but rather that you have difficulty perceiving or distinguishing between certain colours. This is why many prefer the term colour vision deficiency or CVD to describe the condition.   A routine eye exam typically includes colour vision testing so you can confirm if you have normal colour vision.   CVD affects men more than women, appearing in approximately 7% of men  and 0.5% of women  worldwide.  It is more common in males because the gene for colour blindness is on the X-chromosome inherited from the mother.

Having colour vision deficiency means that you perceive colour in a more limited way than those with normal colour vision.   The eyes contain different photoreceptor cone cells that fire in response to a specific colour.   The blue, green or red cone cells allow you to see the depth and range of colours that the normal eye can see. The type of colour blindness and therefore the type of colour vision that is impaired, is based on which of the three cone cells are abnormal. The most common form of CVD is red-green, followed by blue-yellow. Total colour blindness or the complete inability to perceive colour is quite rare. 

Colour blindness can also be the result of eye damage, specifically to the optic nerve, or to the area in the brain that processes colour. Sometimes an eye disease, such as cataracts, can also impact one’s ability to perceive colour. Systemic diseases such as diabetes or multiple sclerosis can also cause acquired CVD. 

Living with CVD

Red-green colour blindness does not mean only that you can’t tell the difference between red and green, but rather that any colour that has some red or green (such as purple, orange, brown, pink, some shades of grey, etc) in it is affected. 

You many not realize all of the ways you use even subtle distinctions in colour in your daily life. Here are some examples of ways that CVD can impact your life and make seemingly everyday tasks challenging:

  • You may not be able to cook meat to the desired temperature based on colour. 
  • Many of the colours in a box of crayons will be indistinguishable.
  • You may not be able to distinguish between red and green LED displays on electronic devices that indicate power on and off. 
  • You may not be able to tell between a ripe and unripe fruit or vegetable such as bananas (green vs. yellow) or tomatoes (red vs green). 
  • Chocolate sauce, barbecue sauce and ketchup may all look the same. 
  • Bright green vegetables can look unappealing as they appear greenish, brown or grey. 
  • You may not be able to distinguish colour coded pie charts or graphs (which can cause difficulty in school or work). 
  • Selecting an outfit that matches can be difficult. 

Knowing that one is colour blind is important for some occupations that require good colour discrimination such as the police officers, railway workers, pilots, electricians etc.  These are just a few of the ways that CVD can impact one’s daily life. So is there a cure? Not yet. 

While there is no cure for CVD, there is research being done into gene therapies and in the meantime there are corrective devices available including colour vision glasses (such as the Enchroma brand) and colour filtering contacts that for some can help to enhance colour for some people. If you think you might have CVD, Dr. Leong and Dr. Bui can perform some tests to diagnose it or rule it out. and discuss options that might be able to help you experience your world in full colour.