THE EYE AND THE WAY IT WORKS

In the first section, we have seen the main structures of eye and got a better understanding of it. But how do these structures associate with each other to carry out the work properly? We are going to find out in the following. When we look at something, light rays first enter our eyes through the cornea. Due to the curved surface of the cornea, the light rays will be bent (refracted) and then squeezed closer together to pass through the pupil. After that, the refracted light rays pass through the clear lens (about the size and shape of a M & Ms chocolate bean) which have two surfaces. Therefore, these light rays are bent two more times on their way to the back of the eye.

As the light rays continue their trips, most of them will pass through the vitreous humor, a clear jelly-like substance fills the space between the back of the lens and the retina. Lastly, the rays reach the retina, the inside lining of the back surface of the eye which contains specialized cells which convert light energy into electrical impulses. These cells are rods, for black and white images, and cones, which are for colour images.

Part of these photo-sensitive cells in the retina is a six-inch appendage of the cell, the axon, which joins with other axons to compose the optic nerve. The electrical impulses pass through the optic nerve to the brain stem, located in the centre of the brain. There, each axon connects with other cells, and the axon of the receiving cells travels another six inches to the back of the brain, the occipital lobe, where it synapses with a brain cell(s) to produce vision and this is the process which enables us to see things.