How your eyes work

Comprising seven converging bones, the orbit helps to protect the eye from injury – forming a pyramid-shaped socket in which the eyeball rests.

Cushioned by a layer of protective fat, the eyeball is made up of three layers, with three chambers of watery fluid which provides nourishment and helps to keep the eyeball inflated.

Running from the back of the eyeball, the optic nerve transmits visual information to the brain, with other nerves in the eye sending messages about pain or helping to control movement.

The cornea is the clear portion of the eye that covers the iris and the pupil. It takes up about one-sixth of the eye, with the rest being opaque.

The iris is the coloured ring of tissue that surrounds the pupil. Working in the same way as a camera aperture, the pupil controls the flow of light into the eye – closing in bright light and opening in the dark.

Sitting directly behind the iris, the lens focuses rays of light onto the retina, which, via photosensitive cells, converts light into electrical signals which are carried to the brain by the optic nerve.

Eyelids play a crucial role by protecting the surface of the eye from scratches, dust and foreign objects. They also help to lubricate the surface of the eye when we blink.

There are several tear glands in and around the eyelid, each with as many as 12 tear ducts. These keep the cornea moist, while protecting its delicate cells. Tears drain away via a small opening in the inner corner of the eyelid.