Sight is our most used sense contributing more than 75% of all knowledge that we learn throughout our lifetime. The eye is a small organ yet is capable of seeing objects, as tiny as a grain of sand, and as distant as a star. It allows us to focus on objects near and far, as well as distinguish between millions of colors. Actually, we don 't see objects, only the light they reflect which is interpreted as visual images.
Firstly, the cornea, which is responsible for the majority of the eyes focus, takes a wide spectrum of light which refracts or bends it through the pupil, the round opening in the centre of the iris. From the pupil the light travels through the lens where it is focused even more finely and directed to the retina. The retina changes the light information into electrical impulses and sends them through the optical nerve to the brain where they are processed into pictures.
| Vitreous humour | The transparent jelly-like fluid filling most of the volume of the eye. |
| Sciera | The tough, white outer layer of the eyeball. |
| Choroid | The layer immediately behind the retina consisting of blood vessels that nourish the outer part of the retina. |
| Retina | The inner layer of the eye containing cells, which convert light, rays into electrical signals, which are transmitted to the brain to be processed. |
| Macular | The small central area of the retina responsible for colour and fine detail vision. |
| Optic nerve | The cable of nerve fibres which transport signals from the retina to the visual centres of the brain where they are processed into images. |
| Lens | A transparent disc-shaped structure inside the front of the eye, which changes shape to focus light rays entering the eye. |
| Pupil | The 'hole' in the centre of the iris through which light enters the eye. |
| Cornea | The clear window at the front of the eye that does most of the focusing of light rays on to the retina. |
| Iris | The coloured part of the eye which changes the size of the pupil to control the amount of light entering the eye. |
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