Ocular Anatomy And
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The Eye A Biological Camera
The eye fuctions much like a camera. Light passes through the cornea and the lens
of the eye and is focused on the retina in much the same way that an image is
focused
on the film of a camera.
The cornea and the lens are transparent and bend light rays in such a way that an image is projected onto the retina. The iris, the colored part of eye, contains the pupil which controls the amount of light entering the eye in much the same way as the shutter of a camera controls the amount of light entering a camera. The light rays then pass through the vitreous cavity that is filled with a clear gelatinous material and are finally focused on the retina. The image on the retina is then transmitted to the brain through the optic nerve. This is the basic mechanism of vision.
Anatomy Of The Retina
The natural lens of the eye is located behind the colored part of the eye known
as
the iris. the lens is like a magnifying glass. The lens is transparent and helps
to focus
light rays onto the retina in the back of the eye.
The retina has two parts: the peripheral retina and the macula. If you imagine the retina as a circle with a bull's-eye at the center, the macula is like the bull's-eye: it is very small. It is located near the optic nerve. The large area of retina that surrounds the macula and makes up 95% of the retina is called the peripheral retina. The peripheral retina gives us vision to the side, this is called "peripheral" vision. This is what we refer to when we say, " I saw something out of the corner of my eye". Because the peripheral retina cannot see detail clearly, we cannot use peripheral vision to read, thread a needle, drive, or even recognize a face. If I see someone off to my side, "out of the corner of my eye", I can tell who the person is by his or her general shape, but I won't be able to see the expression on that person's face. 
In order to see fine detail, we must look straight ahead, using the macula, the bull's-eye center of the retina. Though the macula makes up only a small part of the retina, it is one hundred times more sensitive to detail than the peripheral retina. The macula allows us to see tiny detail, to read fine print, recognize faces, thread a needle, read the time, see street signs, see grains of salt being poured from a shaker, etc. If you look at the above image, where the word "macula" is seen in red letters and you look directly at that word, you are looking at it with your macula. If you keep your eye fixed on the word "macula", you are aware of the other words in the picture because of your peripheral vision, but you won't be able to read any of the other words clearly. If you can read them clearly, it is because you are looking at those words instead ofthe word "macula". The only way to see detail is by using your macula and it must be healthy to work properly.
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