our eyeballs are used by our bodies as one way of sensing the outside world. They consist of several layers of tissue containing a very clear gel called vitreous humour in ball. At the front of this is the another very special type of tissue forming the lens of our eyes, which again must be very clear to allow light to pass through. There are several layers of protection over this lens as it is very important for our sight. Light passes through this lens, through the clear gel in the centre and hits the back wall of this ball, where it is sensed by a tissue called the retina. These are converted into electrical signals which are transported down the optic nerve to the brain, where your brain makes up a picture based on this.