Picture yourself standing before a mesmerizing painting, its vibrant colours narrating a story beyond words. Imagine those colours are subtly altered, blurring the lines between shades and hues. For individuals with colour blindness, this is their reality—a world where the perception of colours is uniquely different.
Join us as we embark on a captivating expedition, exploring the intricate science of colour vision, delving into the numerous forms of colour blindness, and uncovering the enigmatic causes behind this troublesome phenomenon.
- In every rainbow, the colours consistently emerge in a specific sequence: red, orange, yellow, green, blue, indigo, and violet. Each hue in the rainbow’s chromatic spectrum is associated with a distinct light wavelength. Colours on the red end of the spectrum possess longer wavelengths, while those on the blue end have shorter ones. Many light wavelengths exist, corresponding to the vast array of colours we perceive.
- Think of your eye as a camera. The front part has a lens. Its job is to focus images on the inside of the back of your eye. This area is called the retina. It’s covered with special nerve cells that contain pigments that react to light.
To see anything, we need tiny little helpers inside our eyeballs, the so-called photoreceptors. There are two different types of them: rods and cones. Both sit on the retina at the back of the eye and pass the information on to the brain. The rods are sensitive to light while the cones pick up colour.
- Each of the cones carries one out of one of three different photopigments – red, green, and blue – and reacts differently to coloured light sources. Each of these three types has a specific colour absorption curve with peaks at different points in the colour spectrum.
- Now, when one type of cone malfunctions, the colour, this cone would normally absorb is altered. This changes colour perception, resulting in a (somewhat) different way of perceiving colour. This is what we call colour blindness.
Types of colour blindness
- There are different types of colour blindness and in extremely rare cases, people are unable to see any colour at all, but most colour-blind people are unable to fully ‘see’ red, green, or blue light.
- The affected cones can be mutated or defective in each case.
- A mutated cone causes a slight shift, and a defective cone causes a bigger shift in colour perception.
- This results in a total of six possible types of colour blindness.
The green-red inefficiencies are the most common ones:
- Deuteranomaly: malfunctioning green cone (common): It happens when the green cone photopigment doesn’t work as it should. Yellow and green look redder, and it’s hard to tell blue from violet.
- Deuteranopia: missing green cone (rare): When there are no working green cone cells, reds may look brownish-yellow, and greens may look beige.
- Protanomaly: malfunctioning red cone (rare): When the red cone photopigment doesn’t work as it should, orange, red, and yellow look greener, and colours are less bright. It’s usually mild and doesn’t cause problems in daily life.
- Protanopia: missing red cone (rare): There are no working red cone cells in this case. The colour red simply looks dark grey. Some shades of orange, yellow, and green look yellow.
Blue-type colour blindness’ is also possible but very rare:
- Tritanopia: missing blue cone (very rare): Your blue cone cells work in only a limited way. Blue looks greener, and it can be hard to tell pink from yellow and red.
- Tritanomaly: malfunctioning blue cone (very rare): Also known as blue-yellow colour blindness, you have no blue cone cells. Blue looks green, and yellow looks light grey or violet.
Complete Colour Blindness or Monochromacy: No colour is visible, and the vision may not be as clear.
There are two types:
- Cone monochromacy happens when 2 of the 3-cone cell photopigments — red, green, or blue — don’t work. When only one type of cone works, it’s hard to tell one colour from another. And if one of the faulty cones is blue, the vision may not be as sharp, the person may be near-sighted, and may have uncontrollable eye movements, a condition known as nystagmus.
- Rod monochromacy, or achromatopsia, it’s the most severe form of colour blindness. None of the cone cells has photopigments that work. As a result, the world appears black, white, and grey. Bright light may hurt the eyes and may have uncontrollable eye movement (nystagmus).
Causes of Colour Blindness:
Usually, genes inherited from parents cause faulty photopigment molecules that detect colour in the cone-shaped cells, or “cones,” in the retina.
But sometimes colour blindness is not because of the genes, but rather because of:
- Physical or chemical damage to the eye
- Damage to the optic nerve
- Damage to parts of the brain that process colour information
- Cataract: a clouding of the eye’s lens