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What is Cornea?

November 29, 2010 Leave a comment

The cornea can be said to be a very important part of the eye. It is located in the front portion of the eye and is transparent. The cornea provides a wrap for the anterior camber, iris and the pupil. It works as a protective shield and does not let germs and other harmful particles affect the eyes. It also controls the penetration of light and helps in focusing. It along with the lens is responsible for refracting light and helps the eye focus. The Cornea is accountable for most of the (approximately 2/3rds) optical power of the eye. The cornea is very sensitive because of the unmyelinated nerve ending. It is sensitive not only to touch but also to chemicals and temperature. The reflex action can be seen when it is touched as it involuntarily causes the eyelid to close. It is probably the most sensitive tissue in the human body. A very interesting fact about the cornea is the absence of blood vessels. Because it is absolutely essential that the cornea remains transparent, the blood vessels are absent. Another interesting fact is that the cornea has 5 layers. Let us briefly look at the 5 layers of the cornea:

1. Corneal Epithelium: is a tissue layer which is multicellular. They grow rapidly and the cells are easily regenerated. This layer stays moist due to tears.
2.   Bowman’s Layer: is a very strong layer in the cornea. It provides a protection to the corneal stroma. The layer is 8-14 microns in thickness.
3.   Corneal Stroma: this is the middle layer of the cornea. This is probably the thickest part of the cornea as 90% of the thickness is that of the stroma. It is made up of type 1 collagen fibrils having close to 200 layers.
4.   Descemet’s Membrane: is a very thin layer that functions as a customized base membrane of the corneal endothelium.
5.  Corneal Endothelium: is the layer which regulates the flow of fluid and solute between 2 compartments i.e. the corneal stroma and the aqueous.

In refractive surgeries, the corneal shape is changed due to which the person can avoid using corrective lenses. Most advanced techniques use lasers which help in reshaping the cornea.