By Dr S.S. Gill
Ipoh Echo’s EYE HEALTH series continues with Consultant Eye Surgeon Dr S.S. GILL talking to us about Colour Blindness or Colour Deficiency.
So many of us take the ability of seeing colours for granted. Every year, 17 year olds undergo colour vision assessment as part of their drivers’ licence test. A fraction of these teenagers are shocked when they find out that they have colour blindness (better called Colour Deficiency). What does colour deficiency mean?
HOW THE EYE FUNCTIONS
The eye is a very sophisticated camera! Inside the eyeball, right at the back of the eye is the layer of the retina where all the nerve cells are. These nerve cells comprise of special cells called Rods and Cones. The Rods have no colour vision function except that they are very sensitive to light and help in our night vision.
On the other hand, the cells responsible for picking up the colour that we see are the Cone Cells. Among these Cone Cells, there are varying degrees of pigment present. Depending on the pigment present in the Cone Cells, they help react to different colours. Some of them respond and pick-up the longer wavelength light like the red colours and some of them respond to the shorter wavelength light like that of blue colours.
CAUSES OF COLOUR DEFICIENCY
Although there are many conditions that can result in Colour Blindness, for most people who suffer from this, it is mainly of genetic cause. This just means that they are born with Colour Blindness. When we say it is genetic, it means that the Colour Blindness has been passed down in the genes from the parents.
In our genes, there are the X and Y chromosomes. The gene which is responsible for Colour Blindness is carried on the X chromosome and so more men suffer from Colour Blindness than women. Women are usually only the carriers but do not normally have Colour Blindness. Worldwide it is estimated that there are some 250 million people who are colour blind to a lesser or greater extent.
TYPES OF COLOUR DEFICIENCY
Colour Deficiency may be mild, moderate or severe. Also, depending on the amount of pigment deficient, it may be divided into:
Red-Green Colour Deficiency – Is the most common type where the reds and greens appear similar (adjacent picture is a simulation of how it would appear)
Blue-Yellow Colour Deficiency – These are less common. Most of the time they also have some concomitant red-green deficiency too.
There has been on-going research in the area of gene therapy for the treatment of Colour Deficiency. Animal studies for this have shown promise where the introduction of a gene (opsin gene) has given the animals colour vision that they did not have before treatment.
In the USA, special kind of spectacles have been developed which are purplish in colour that are able to help those with the most common form of Colour Blindness. These glasses filter out certain wavelengths of light that disturb the perception of colour vision. They are not without trouble though because some things disappear from vision when these glasses are worn in some instances. If you are unsure of whether you have colour deficiency or not, do not hesitate to get your eyes checked.
For more information, call Gill Eye Specialist Centre at Hospital Fatimah (05-545 5582) or email firstname.lastname@example.org.