How Eyes Work

How we see

Seeing is similar to the process of taking a photograph. The retina acts like a camera film which stores an image of what we are looking at. This image is then sent to the brain where it is processed, rather like developing a camera film. We therefore actually "see" with our brain, which uses light information sent from our eyes. This process happens incredibly quickly so that we see everything instantly.

How the eye works

Light rays enter the eye through the cornea and lens which bend the light and focus it towards the retina.

The iris is the coloured part of the eye. It controls the amount of light that enters the eye by changing the size of the pupil, the dark hole in the centre of the iris. The pupil shrinks in bright conditions to let less light in, and grows in dark conditions to let more light in.

The central section of the eye is filled with vitreous, a clear, jelly-like substance which allows light to pass through from the front to the back of the eye.

The retina is a light-sensitive layer of rod and cone cells which collect light signals and send them to the optic nerve. Rod cells are concentrated around the edge of the retina and help our peripheral vision which gives us spatial awareness. They also enable us to see in dim light,and our ability to see movement. Cone cells are concentrated in the centre of the retina, also known as the macula - the point at which the light is focused by the cornea and lens. Cone cells give us the ability to see in detail and colour.

The optic nerve is made up of thousands of nerve fibres which send signals to the brain. The brain then translates the signals into images.