FORESIGHT
Dr. Gary A. Nelles
Optometrist
COLOUR
BLINDNESS
‘Colour blindness’ is a term often used incorrectly. Most people
said to be ‘colour blind’ are actually colour deficient. These people
still perceive colours but not as many as a person with normal
colour vision. They are unable to distinguish between certain
shades of colours.
Inside the eye, we have light receptors called rods and cones.
There are 3 types of cones (red, green and blue) that we use for
colour vision. When someone has fewer of one cone than the other
two, they are unable to detect differences between some colours
and they appear to be the same. Three types of colour deficiency
exist but essentially people will confuse certain shades of red and
green or certain shades of blue and yellow. It is more common in
males (about 7%) than females (about 0.6%).
Although colour deficiency can be acquired (due to trauma
and some medications), most people are born with it. Hence, it is
important that children receive an eye exam including colour vision
testing before entering school since learning materials are often
colour coded. Teenagers may require colour vision testing before
deciding on a career because some occupations like police officers,
pilots and electricians require normal colour vision.
Written by: Dr. Gary A. Nelles
36 Brock St. W., Tillsonburg, 688-5551
New Patients Welcome