Colour Blindness (CVD)

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Colour blindness is a subject or condition hardly talked about due to the disinterest and sometimes ignorance in our society. It is estimated that 1 in 12 men and 1 in 200 women suffer colour vision deficiency worldwide (

It is a deficiency caused by an absence or a reduction in the number of cone cells in the eyes, says Dr. Choice Onyinyechi, of the Medifem Multi-specialist and fertility hospital, in Accra. She further explained that the cone cells are responsible for seeing colour, while the rod cells are responsible for seeing black and white. “When these photoreceptor cells found in the retina, are deficient, the individual exhibits obvious symptoms of colour blindness.”

There are different causes of colour blindness. For the majority of people with deficient colour vision, the condition is inherited from the mother, although others become colour blind as a result of complications from other diseases such as diabetes, multiple sclerosis and also through the aging process.

Colour blindness is an X-linked disorder indicating the causal gene is located on the X chromosome. (Note we said the condition is inherited from the mother). Females have two X chromosomes while males have the X and the Y chromosomes. “It explains why females are largely carriers and do not show visible signs of colour blindness,” said Dr. Onyinyechi.

Most colour blind people are able to see things as clearly as others, but are unable to fully ‘see’ red, green or blue light or violet. Meaning they perceive these colours differently. There are different types of colour blindness and in very rare cases, some people do not see any colour at all.

The most common type of colour blindness called the ‘red/green’ makes sufferers mix up all colours with red or green undertones. The effects of this condition on the individual can range between mild, moderate to severe. Making it for most people negligible for approximately 40 per cent of sufferers because they do not know they have the condition, while the majority of sufferers experience the confusion of mixing up colours in their daily lives. (

To diagnose the existence and the extent of one’s colour vision deficiency, people can be tested using the Ishihara chart or colour arrangement test.

According to Dr. Choice Onyinyechi “as soon a child can identify numbers, and objects, then these specific tests can be used to determine if they suffer colour vision deficiency.”

Explaining the tests, Dr. Onyinyechi stated “the Ishihara test allows the person to identify numbers contained within images made up of different colour codes. Once the individual is able to identify the embedded number, he or she does not suffer the condition. However confusing the number perceived as something else would mean one has colourblindness.”

Within the same spectrum, individuals are made to arrange numbers according to the colours and they may sometimes not identify certain colours and numbers tend to look different to them.

“There is no cure for colour blindness but what happens is that most people are able to adapt over time” says Dr. Onyinyechi. So for example in Europe and America, collaborations between health professionals, policy makers, and industry, has led to strategic development and positioning of certain objects, shapes, colours for people with colour blindness to acquaint with and use them with ease throughout their daily activities.

Colour vision deficiency is not a fatal condition and is usually nothing to be overly concerned about. People just get used to the condition. However it can cause issues with difficulty in learning for youngsters if colours are used to help with learning. They may also lead to people having slightly limited career choices as certain jobs such as pilots, train drivers, electricians and air traffic controllers require accurate colour recognition.

Many people with colour vision deficiency have few difficulties and do live normal lives.

Dr. Choice Onyinyechi, Medifem Hospital, Accra