Colour blindness (colour vision deficiency, or CVD) the decreased ability to see color or differences in color. It affects approximately 1 in 12 men (8%) and 1 in 200 women in the world. According to a study carried out in Nigeria, the prevalence of colour blindness was 2.3% with the rate of  3.8% and 0.9% in males and females respectively.

Types of colour blindness

They include;

Proctanomaly; reduced sensitivity to red light

Deuteranomaly; which is a reduced sensitivity to green light and is the most common form of colour blindness

Tritanomaly; which is a reduced sensitivity to blue light and is extremely rare.

The effects of colour blindness can range from almost normal colour perception to almost total absence of perception of the ‘faulty’ colour.

People with difficulty in seeing red and green colours are collectively known as ‘red-green’ colour blind and they generally have difficulty distinguishing between reds, greens, browns and oranges. They also commonly confuse different types of blue and purple hues. People with reduced blue sensitivity have difficulty identifying differences between blue and yellow, violet and red and blue and green. A colour blind person would see the world as red, pink, black, white, grey and turquoise.

Causes of Colour blindness

Colour blindness can be inherited or acquired. People with inherited colour blindness don’t have a change in their colour vision in which case their ability to see colours will remain the same while the acquired ones can have worsening of their vision or it can improve over time.

Colour blindness is a genetic condition caused by a difference in how one or more of the light-sensitive cells found in the retina of the eye respond to certain colours. These cells, called cones, sense wavelengths of light, and enable the retina to distinguish between colours. This difference in sensitivity in one or more cones can make a person colour blind.

Symptoms of colour blindness

  1. Difficulty distinguishing between colours.
  2. Inability to see shades or tones of the same colour.

Nearly all people who are “colour blind” can see colours but have difficulty distinguishing between certain colours. Not all people who are colour blind have trouble with the same colours – most cannot distinguish between reds and greens; some cannot separate blue from yellow.

A very small group have a condition called monochromatism which only allows them to see black and white.

The symptoms of colour blindness are often observed by parents when children are young. In other cases, symptoms are so slight, they may not even be noticed.


There is currently no treatment for inherited colour blindness. Colour filters or contact lenses can be used in some situations to enhance the brightness between some colours and these are occasionally used in the workplace. For acquired colour vision deficiency, once the cause has been established and treated, your vision may return to normal.