The way that we see bears a strong similarity to how we take a picture with a camera.
In effect we have two cameras (the eyes), which take pictures for us. The back part of the brain is our ‘developing house’ and the images are sent from the eyes to the brain via the optic nerve (actually a bundle of over one million nerves) in the form of nervous impulses, these are tiny little electrical electric pulses.

How is the eye made up

At the front of the eye there is a power system made up of the cornea (the front clear surface that lies in front of the coloured part of the eye), which accounts for approximately two thirds of the power of the eye and a clear lens, which can be changed in power. Between the two structures there is the anterior chamber filled with a clear fluid (aqueous humour) and the iris (the coloured part of the eye). The iris controls how much light enters the eye by causing the pupil (the black central hole formed by the iris) to constrict when there is a lot of light and to dilate when there is less light

The main or posterior chamber of the eye is filled with a jelly like substance called the vitreous humour; the equivalent chamber in a camera would be full of air. At the back of the eye there is a delicate layer of photosensitive material called the retina, it’s equivalent in the camera would be the photographic film. There are millions of receptors on the retina that react when light lands on them and they are of two types, rods and cones. Cones react to brighter lights and are responsible for colour and our high discrimination tasks, rods are used in poorer light conditions. Rods are largely responsible for our judgement of movement and peripheral vision.

There is a hole at the back of the eye called the optic disc and through this passes the optic nerve taking information to the brain which acts as our developing house, deciphering the nervous impulses to create our images or pictures.

The eye is made up of various layers.
The inner layer is the retina, surrounding this is a very blood vessel rich layer called the choroid which feeds the retina. These layers are encased in a tough protective layer called the sclera and this is the layer that looks white when viewed from the outside.

There is a final outer layer of loosely attached transparent skin called the conjunctiva. This layer covers the whole of the front of the eye except where the cornea is and then folds back on itself to become the inside lining of the eyelids.

This is the retina of a healthy teenager.

The light coloured vessels are arteries, the darker vessels veins.
The darker central area is the macula with a brighter central spot called the fovea, sometimes called the ‘yellow spot’. The pale circle is the optic disc where the optic nerve(s) leave the eye. (This image is taken by the retinal camera that we have in the practice and normally we can take a similar image of your eye as part of your eye examination – you instantly see the back of your own eye. We can then save the image on the computer for future reference).