All about eyes - anatomy

The iris is the coloured part of the eye. It controls how much light enters the pupil and has tiny muscles that makes the pupil size bigger and smaller. The colour, texture and pattern of each person’s iris are as unique as their fingerprints.

The pupil is a hole at the centre of the iris. The size of the pupil decides how much light enters the eye. The size is controlled by the muscles in the iris.

Doctors often look at how the pupil responds to light to check that your visual system is working correctly. An increase in normal light makes the pupil get smaller and a decrease in light will make it grow bigger.

The sclera is the outermost layer that surrounds the eye. The front part of the sclera becomes the cornea at the very front of the eye.

It is made up of a rough, shiny white tissue and is there to protect the eye and give it stability to help keep its shape.

The cornea is a dome shaped covering found at the very front of the eye. It is very transparent yet helps protect the eye from outside damage. It is half a millimetre thick. 

The lens is transparent and sits behind the iris.  Its job, along with the cornea, is to focus light on the retina at the back of the eye.

The lens is held up in the eye by fibres which are attached to the ciliary muscle.

The ciliary muscle changes the shape of the lens so that you can focus on objects at different distances.

The retina is at the very back of the eye. It contains millions of cells that are sensitive to light.

The retina takes the light the eye receives and changes it into electric signals, sending them to the brain so that we can understand what the eye is seeing.

The macula is the small sensitive area of the retina responsible for the central part of our vision.

It provides vision for fine work and reading.

The vitreous is a gel like material between the lens and the retina. After light passes through the lens, it shines straight through the vitreous to the back of the eye.

Vitreous gives your eye its form and shape.

The conjunctiva is a mucous membrane that is on the inside of the eyelids and on the surface of the eyeball.

The conjunctiva lets out oils and mucous that moisten and lubricate the eye.

The aqueous humour is a clear fluid that fills the space between the cornea and the iris. It is produced by a part of the eye called the ciliary body which lies just behind the iris.

Aqueous is important in controlling the pressure inside the eye and giving the front of the eye its shape.

The optic nerve connects to the back of the eye near the macula and carries the messages from the retina to the brain.