The Structure of the Eye
By fred jones
The human eye is an amazingly complex and delicate structure that really is really fascinating to look at in detail. It is amazing to think that these small structures are able catch and help process the environment around us with such acuity and clarity.
The structure of the eye is pretty neat when looked at. First the enveloping membrane of the eye is called the sclera. It is a rather firm outer layer and is seen as the white areas surrounding the pigmented iris. The cornea is like the sclera in that it acts as an outer cover for the eye, however it is clear allowing for the passage of light. Inside the cornea we have the aqueous humor. This is a jelly like substance which acts as a buffer between the cornea and the lens/iris.
The iris is the colored part of the eye. Its main function is to constrict and dilate to adjust the amount of light that passes through to the nerves. The lens is pretty much exactly what it sounds like. It is a lens that changes its shape to adjust the focus of the images you are seeing. Making up a large part of the eye is the vitreous humor. This is very much like the aqueous humor in that it is a jelly like substance that is important in giving shape and some rigidity to the eye. It pretty much fills the entire inside area of the eye. Lining the inside of the back of the eye is the retina.
The retina contains rods and cones which serve as an agent to process the incoming light into a signal which the brain can process into an image. In the retina is an area called the fovea which is a depression in the retina containing a very high amount of cones and rods. Because of the densely packed receptors, the incoming light that hits the fovea is processed with the highest resolution and clarity. In other words, the fovea would be the area that receives the signals of the object you are concentrating your gaze on. Behind the retina, and in front of the rear sclera, is the choroid.
The choroid is a darkly pigmented layer that absorbs excess light that has been taken in. The choroid is a very important structure because it helps to sharpen the incoming images by removing any excess light that would blur the image. It is like when you step out of a dark room into the sunlight. Until your eyes adjust, there is a bleaching effect where you cannot process images well due to the excess light and the high activation of the rods in your eyes. The choroid helps to remove some of the excess light. Connecting the retina to your brain is the optic nerve. The optic nerve collects all the information from the rods and cones in your retina and sends the signals to your brain to be processed into images.
An interesting fact about the human eye is the blind spot. We all have it and it isn't some kind of disease or mutation. The blind spot is actually a part of the retina called the papilla where there are no rods or cones because it is the area where the optic nerve is attached. Because there aren't any rods or cones it creates a blind spot in your vision. The reason we do not see a blind spot normally is because our brain helps to filter out this spot by compensating the area and filling it in. A quick test can be done to find your blind spot. Hold up two pens in front of your face. Focus your gaze on one that is directly in front of you and slowly move the other to the outside. At one point the pen or part of the pen should disappear. That is where your blind spot is. Neat isn’t it?
About the author
Fred Joneslasik from http://www.FreeArticlesAndContent.com
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