Color Blindness or Color Vision Deficiency

Colour vision deficiency is the inability to distinguish certain shades of color under normal lighting conditions. The term “color blindness” is more commonly used to describe this visual condition, but very few people are completely color blind.

This condition affects males much more often than females. In general, the prevalence is 1 in 12 males and 1 in 200 females of the population has a color deficiency.

What causes Colour Vision Deficiency?

Colour vision is possible due to photoreceptors in the retina of the eye known as cones. These cones have light-sensitive pigments that enable us to recognize color. Found in the macula (the central part of the retina), each cone is sensitive to either red, green, or blue light. The cones recognize these lights based on their wavelengths.

Normally, the pigments inside the cones register different colors and send the information through the optic nerve to the brain. This enables us to distinguish countless shades of color. But if the cones lack one or more light-sensitive pigments, we will be unable to see one or more of the three primary colors.

What are the different types of Colour Vision Deficiency?

Most people with color vision deficiency can see colors, but they have difficulty differentiating between particular shades of reds and greens (most common), blues, and yellows (less common). These two forms of color vision deficiency disrupt color perception but do not affect the sharpness of vision (visual acuity).

People who are totally color blind, a condition called achromatopsia, can only see things as black and white or in shades of grey.

Colour vision deficiency can range from mild to severe, depending on the cause. It affects both eyes if it is inherited and usually just one eye if it is caused by injury or illness. People who suffer from color vision deficiency can have a harder time differentiating between the colors, which can depend on the darkness or lightness of the colors.

In both cases, people with color vision deficiency often see neutral or grey areas where a particular color should appear.

Normal Vision


Deuteranopia – usually confuses the difference between green/red, red/brown, etc.


Protanopia – usually confuses the difference between red/black, blue/purple, etc.

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Tritanopia – usually confuse the difference between blue/green, orange/red, etc.

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Importance of Early Detection

In a local study, 33 out of 1,250 teenagers were discovered to have color vision deficiency. This is a relatively high number of teenagers diagnosed, most of whom are only diagnosed after primary school. Vision screening in local schools currently includes only visual acuity and stereopsis.

Early detection is the key to overcome limitations created by color vision deficiency. Color vision deficiency may not be life-threatening but it does affect the quality of life. Some patients may suffer from its long-term consequences, as they may be mistaken as slow learners in school or being uncooperative during play. All these could lead to poor self-esteem and symptoms of social withdrawal in children.


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