Check-up; Development and treatment of colour blindness

March 29, 2016

Dear Readers,

Don B. is a 22-year-old young man who writes to share that he has only just discovered that he is colour blind. He says he is not fully colour blind, but has discovered that he has vision problem with red and green colours. He recently discovered this when he went to get tested for glasses and had his eyes checked; he never knew he had a problem before. He asks how this could have happened as no one else in his family has this problem, and what does it mean?

Colour blindness, or colour-vision deficiency, is the inability or reduced ability to see colour or distinguish colour differences. There is no actual blindness! Red-green colour-vision defects occur mainly in men and there are no other visual abnormalities associated with this. In fact, some males with a mild red-green colour deficiency may not be aware of the problem until tested for some reason (medical, etc). This visual defect actually occurs in three to four per cent of males of African descent. It is important to know when this problem exists as early as possible as this finding can affect occupational choices.

There are three main kinds of colour blindness, red-green, blue-green or total colour blindness. Total colour blindness is very rare. The negative effects of colour blindness can be almost minimal for some people, and the ability to perceive colours improves in good lighting and deteriorates under poor light.

Colour blindness can be inherited or acquired through illness or injury. When it is inherited, the colour vision will always remain the same. When it has been acquired, then colour vision can worsen or improve over time.

Sometimes, colour blindness is caused by damage to the eye, the optic (eye) nerve or to parts of the brain which process colour information. Colour vision can also decline with age, often because of cataracts which cloud the eye lens. Causes of acquired colour vision defects include:

• Ageing

• Glaucoma

• Cataracts

• Eye injury

• Medication side effects

• Parkinson's disease

• Optic neuropathy

• Pituitary gland failure

The symptoms of colour blindness vary:

• Person may see some colours but not others (e.g., mixes up some reds and greens but sees blue and yellow easily).

• Person can see so many colours that they are not aware of any defect.

• Person can see only a few shades of colours.

• Rarely, person sees only in black, white and grey.

In one type of test to measure colour deficiency, the person looks at a set of coloured dots and tries to find a pattern of numbers or words in them.

Most people who are colour blind can see colours, but certain colours appear washed out and are easily confused with other colours.

Inherited colour-vision problems cannot be treated or corrected at this time in medicine. For the most common occurring red-green colour deficiency, no treatment is needed because the person functions normally. Often, the person is not aware that they see colours differently from anyone else!

Some acquired colour-vision problems can be treated, e.g., a cataract can be surgically removed and normal vision restored. It also seems that wearing coloured contact lenses and glasses which block glare will also help lessen the disability, if this is needed. Learning to look for colour cues such as brightness or location also helps. For example, the order of the three coloured lights on a traffic signal is well known and one can determine which light is lit up.

Discovering colour deficiencies early can prevent learning problems and poor esteem in school and allows at an early stage for informed career choices.

Write to:

Check Up,

PO BOX 1731,




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