COLOR VISION DEFICIENCY
What is color vision deficiency?
The nerve cells which receive and process light at the back of the
eye – the retina – are of two main types: the rod-like cells, which
operate at night and the cone-like, which allow us
to see fine
detail and colors by day. Three different chemicals can be found within the cone
nerve cells, so that each cone responds best to
red, green or blue light in a similar manner to
The fault of defective color vision lies in one set of chemicals,
controlling principally either red or green colors.
Only a third of those with color vision problems have the more severe form, where one sort of chemical is completely lacking and very strong colors are frequently confused, though still within a limited range of up to ten main colors. Complete color deficiency, where all colors are seen as varying shades of black and white is extremely rare.
Why are more men than women color deficient?
Like many other medical conditions, defective color vision may
be inherited and carried through
the mother (whose vision will be
apparently normal) to the son. Frequently, brothers within the
same family are affected, but this is not always the case as there
is only a 50/50 chance that sons
of ‘carriers’ will have altered
Will inherited color deficiency change with age?
No. The inherited alterations to color vision involve both eyes and remain stable throughout life.
Can one develop color deficiency?
Yes, but not in the inherited form. A whole range of prescribed
drugs, systemic conditions such as
diabetes, multiple sclerosis
and cardiovascular disease (including high blood pressure), some
diseases and many eye diseases, can affect the cone receptor, color vision may be temporarily or
often in one eye at a time. Difficulty in color discrimination may
be noticed with other visual problems, such as overall blurring of
near or distance vision, or gaps in the field of
vision. Women and men are equally at risk.
Glaucoma, cataract and most eye problems affecting the retina or nerve pathways to the brain can give gradually worsening problems with many different colors, including blues and greens.
Since color vision changes can be an early indication of disease or a side effect of prescribed medication, it is important that you consult your doctor if you are aware that your appreciation of colors is changing.
Can color deficiency be a handicap?
Color is relevant to many aspects of everyday life and some jobs and careers do involve some degree of color identification.
Many large companies involved with printing inks, textiles, paints and electronic components screen prospective employees and may refuse entry for certain jobs if color perception is inadequate.
Despite the introduction of instruments for color
matching, the human eye is still the most sensitive
Can anything be done to correct color deficiency?
Although nothing can replace a faulty mechanism in the retina of
the eye – which is essentially a part
of the brain – many color
defective people do learn ways of compensating for their difficulty
experience and help from relatives and colleagues. It is
important that good lighting is always
How can I have my color vision tested?
Straightforward clinical tests have been devised to screen for defective color vision, most taking only a matter of minutes. These involve reading colored numbers from a book or arranging colored papers in order, or naming colored lights.
Optometrists can give such a test as part of an eye examination. Some school medical examinations may include color vision tests. If a detailed evaluation of color vision is required, a professional opinion should be sought.
- Information provided by the American Optometric Association -