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The Human EyeThe human eye is a complex anatomical organ that remarkably demonstrates the architectural wonders of the human body. Like a camera, the eye is able to refract light and produce a focused image that can stimulate neural responses and enable us to see.
The eye [1] is essentially an opaque eyeball filled with a water-like fluid. In the front of the eyeball is a transparent opening known as the cornea. The cornea has the dual purpose of protecting the eye and refracting light as it enters the eye. After light passes through the cornea, a portion of it passes through an opening known as the pupil. Like the aperture of a camera, the size of the pupil opening can be adjusted by the dilation of the iris. It is a diaphragm which is capable of stretching and reducing the size of the opening. In bright-light situations, the iris adjusts its size to reduce the pupil opening and limit the amount of light which enters the eye. And in dim-light situations, the iris adjusts so as to maximize the size of the pupil opening and increase the amount of light which enters the eye. Light which passes through the pupil opening, will enter the imaging lens that is made of layers of a fibrous material. Unlike the lens on a camera, the lens in the eye is able to change its shape and thus serves to fine-tune the vision process. The lens is attached to the ciliary muscles. These muscles relax and contract in order to change the shape of the lens. By carefully adjusting the lenses shape, the ciliary muscles assist the eye in the critical task of producing an image on the back of the eyeball. The inner surface of the eye on which the image is focused is known as the retina. The retina contains the rods and cones which serve the task of detecting the intensity and color of the incoming light. An adult eye is typically equipped with up to 120 million rods which detect the intensity of light and about 6 million cones which detect the color of light. These rods and cones send nerve impulses to the brain. The nerve impulses travel through a network of nerve cells. There are as many as one-million neural pathways from the rods and cones to the brain. This network of nerve cells is bundled together to form the optic nerve on the very back of the eyeball. The brain on receiving these impulses
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