Anatomy of eyes.

Eyes are one of the most important parts of our body. They work very similar to camera. Eyes basically convert light into electric signal. Light enters into eyes through cornea. Eyes have pupil which control the amount of light entering our eye. Light then passes through lens which forms an image on retina. Retina has rods and cons cell which convert image into electric signal. Naturally we ought to take best care of this sensitive part of our body. Our senses are the input mechanisms for us to perceive the world and act. Eyes are perhaps the most important of our five senses. They are most sensitive organ. Eyes are perhaps the most favorite body part of poets, they are said to reflect emotions of the being. We rest with our eyes closed, we are said to have closed eyes when we die.

Structure and Working of Eyes and its function

Human eyes are basically designed in two parts- front part, which comprises of lens, cornea and iris; and the interior part which comprises of vitreous, retina and veins.Cornea is the transparent structure found in front of our eyes. Light enters into our eyes through cornea which focuses most of the light. Then light passes through lens and gets further focused.  Behind the cornea is iris. It is a colored, ring shaped membrane. The iris has a circular opening called pupil. Pupil can expand or retract to control the amount of eyes entering our eyes. The pupil may take some time to react to light- that is why eyes take time to adjust to low light.The lens is surrounded by muscles which keep the lens in place. These muscles can relax to flatten the lens or contract to thicken the lens. The lens in our eyes is a convex lens- the surrounding muscles make it of variable focus length. When lens is flattened the focus length is high thus we are able to see far away, and when the lens is thickened, the focus length is small and we can see closer objects.

 The interior chamber of eyeball is filled with vitreous humor. After the light crosses lens, it passes through vitreous humor to reach retina. Retina is like the film in camera. It acts as screen for the image formation. Interesting thing to note here is that the image formed is inverted! This happens because of the convex lens in our eye. And only real image formed in a convex lens are always inverted. It is the magic of our brain that interprets the things right way up.Retina has three tissue layers. The first layer is called sclera which gives eye most of its white color [2]. The middle layer is called choroid which contains blood vessels that supply the retina with nutrients and oxygen and remove its waste products. Retina has millions of light sensing nerves. These nerves are called rods and cones because of their shape. Cones are concentrated in the center of the retina. Cones work more in bright light. They provide clear, sharp central vision and detect colors and fine details. Rods and cones convert light in electric signals. This signal is sent to brain via optical nerves which interprets the signal. Rods are located outside the center of retina. They extend all the way to the outer edge of the retina. They provide peripheral or side vision. Rods also allow the eyes to detect motion and help us see in dim light and at night.

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