Retina

Retina - At the very back of the eye is the retina. The picture that is registered on the retina, is then sent trough the visual nerve into the brains visual centre.

The retina consists of visual cells that transfer light to chemical and the electric signals that can be interpreted by the brain. The visual cells that receive the light are called light receptors and there is two variants: Rods and Cones. Their names come from the shape of the cells.

The rods are very light sensible, but cannot interpret colours. They are all over the retina except in the yellow spot there are only cones. If you want to see the yellow spot, you can test to look little besides that you try to see. The light will fall beside the yellow spot and the rods in the rest of the retina can record the light.

There are three kinds of rods that are sensible for colours. The rods are in yellow spot there they are sitting very tight and make us able to have a sharp picture of the world. The yellow spot is a small part of the retina. The rods are less light sensible as the cones.

The spot there the visual nerves leave the retina o visual cells does exist. This spot is called the papilla. You can also notice that the retina is "upside-down", so the rods and cones are behind the other visual cells, so the light must first pass this before they can receive the light.