Our Eyes

How Our Eyes Work

Light (from the sun or an artificial light source) travels in a straight line. It bounces off objects and into our eyes. Light first passes through the cornea, the clear, dome-shaped surface that covers the front of the eye. The cornea bends (refracts) the incoming light, which then passes through the pupil. The iris, the coloured part of the eye, regulates the size of the pupil by stopping too much light entering the eye when it is bright and maximising the amount of light entering the eye when it is dark. The light then passes through the lens, which focuses the light onto the back surface of the eye, the retina. The eye changes the shape of the lens as we look at far or near objects to keep them in focus – this is called accommodation.

The retina is the thin, delicate, light-sensitive tissue that lines the back of the eye. It contains “photoreceptor” cells that convert light into electrochemical signals. The signals are processed and travel from the retina to the brain through the optic nerve, a bundle of about one million nerve fibres. The brain processes the signal to create the image that you see. The image received on the retina is actually upside-down – as an infant, our brains learn to invert the image so we don’t get confused.