Seeing in Full Colour
The retina, which lines the back of the eye, is made up of different cells. The main cells are photoreceptors which respond to light - there are two main types - rods and cones.
There is one type of rod, they are very sensitive and allow us to pick up even the faintest light in the dark, so they are principally used for night vision. There are three types of cone cell, red, blue and green, and each responds to those colours.
If someone is colour deficient there is a problem with the cones, which are usually present but don't respond properly. Generally the red and green cones are affected. It is possible for the cones to be absent, and giving a much more intense deficiency in colour vision, colour blindness. You would only see in black and white, and as you would have just the sensitive rods, you would be very light sensitive too.
Causes of Colour Deficiency
It can be related to DNA and genetic makeup, so if there is a family history it can be passed onto children. It generally passes on the mother's side but can be completely random with no family history. It is rare in girls - around 0.5%, more common in boys around 8%.
It is possible to become colour deficient in later life, due to a pathology rather than a genetic condition, and as such is often reversible. Simple conditions like cataract can affect colour perception, and other conditions, including side effects of medication can cause changes.
Colour Deficiency and Career
As you can be born colour deficient and it will not change, early awareness is important as it can restrict your choice of career. We ask the patient to tell us what they can see on colour test charts.
Colour deficiency can be a problem in the emergency services and armed forces, and it can also affect subjects where colour is important, such as design, chemistry, geography or for electricians. Your Optometrist can test you and advise of any career restrictions.