Cornea A Concavo Convex Lens

The cornea is a part of the eye and it is transparent, it performs an important part in the entry of the light in the eyes. It covers the parts of the eyes like the iris pupil and the anterior chamber. The cornea is the best example of the concavo-convex lens. The cornea also plays a very important part the focusing of the light on the retina.

Structure of the cornea

The cornea also has the sensitive nerve endings that are sensitive towards the touch temperature, chemicals. If some foreign body enters the eyes and comes in touch with the cornea, it senses it and causes a reflex that makes the eyes to close. We can divide it into five different layers. These different layers possess different types of cells.

The cornea composes of a tissue that does not have any blood vessels. This is for the provision of the transparency for the passage of the light. It has a different mechanism for the derivation of the nutrients and oxygen. It gets oxygen directly from the air and it derives its nutrients from the surrounding tissue. In a human eye, it has a diameter of 11.5 mm and a thickness of 0.5mm to 0.6 mm in the central region and approximately of 0.6 to 0.8 mm in the peripheral region.

The general refractive power of the cornea is around 43 dioptres. This constitutes the two-third of the total power of the eye.

The working of the cornea

The cornea is the outer most part of the eyes. Therefore, whenever any light falls on our eyes it first falls counteracts with the cornea. As the cornea is also transparent and it has a good refractivity it is the first one to refract the light, before the lenses does it. Though it is a concavo-convex lens, it does more the job of the convex lens than the concave lens. Therefore, it focuses the light on the lens. This focusing of the light on the lens has some advantages as more light falls on the lens and this makes a sharper image possible.

Moreover, than the focusing of the light the cornea also does not allow the harmful ultraviolet light to fall on the lens and then, transmit to the retina.

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