How The Human Eye Works.

Oh, I know I said film review was next up, but hey, it's my blog, I'm allowed to change my mind ! I was pondering the other day, as is my want, about what life would be like without the sense of vision. This got me researching how the eyes actually work. What follows is a BRIEF paraphrase of what I found....

The eyes are the windows to the soul, they say. When your eyes meet across a crowded room, what happens ?!! Imagine, if you can, NOT having a sense of sight...

The eye is approximately the size of a ping pong ball and sits in a socket in the skull. The white of the eye is named the sclera, and is a fibrous membrane that, along with the cornea, forms the outer covering and protection of the eyeball. The cornea is transparent, or completely clear, which allows light to pass through it. It helps the eye to focus.

Behind the cornea are the iris and pupil. The iris has muscles attached to it that change its shape, controlling the amount of light that passes through the pupil. It is the pupil that allows light to enter the eye. Between the iris and cornea is the anterior chamber. This chamber is filled with a special transparent fluid that gives the eye oxygen, protein and glucose to keep it healthy.

After light enters the pupil, it hits the lens, which sits behind the iris and is clear and colourless. It is this part of the eye that focusses light on the back of the eye - the retina. The retina is smaller than a 10cent piece and holds millions of light sensitive cells. The retina's job is to convert light signals to nerve signals so that brain can process what is being seen.

The lens is suspended in the eye by fibres that are attached to the ciliary muscle. It is this muscle that changes the shape of the lens to accommodate the distance at which you are viewing an object. When you look at things close up, the lens becomes thicker to focus the image clearly onto the retina. Conversely, when you are looking at something in the distance, the lens becomes thinner.

The retina uses special cells called rods and cones to process light. There are about 120million rods and 7 million cones contained in each eye. It is these cells that are responsible for converting the recieved light into impulses which are, in turn, carried to the brain by the optic nerve.

So now you know how the eye works - go feed your ocular hunger !!

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