The science of eyesight

Vision - when you think about it, it seems impossible, right?

Our eyes are complex. In simple terms, radial muscles in the iris contract and relax to alter the size of the pupil and allow light in. The light passes through the cornea before moving into the lens. The light is bent and focused down to a point in the retina, which sits at the back of the eye. The retina has millions of light-sensitive receptors called rods and cones. Each of these has a pigment molecule which changes shape when light comes into contact with it. This triggers an electrical signal that travels via the optic nerve to the brain.

We are used to seeing in colour, so it may come as a surprise that most animals do not. In actual fact, our human eyes can only detect three colours - reg, green and blue. It's our brain that combines these three colours to build millions of different shades. The cone cells which were discussed earlier are the colour detectors in our eyes, while the rod cells can only detect light and not colour. Over half of our cone cells detect red light, around a third detect green light and approximately just 2% of our cone cells can detect blue light.

Many animals can only see in black and white (dichromatic), some can even see four colours (ultraviolet or infra-red). Eyes are magical and it's hard to believe that they weren't created by design!