The CORNEA is the clear "windshield" in the front of the eye. It is the
stronger of the two focusing structures inside the eye. In a healthy eye, the cornea is
completely clear. Disease processes can cause the cornea to lose its clarity, resulting in
decreased sight.
The cornea has five layers: epithelium, Bowman's layer, stroma, Descemet's membrane
and the endothelium. The healthy cornea has no blood vessels within it. It receives all of
its nutrients from the tearfilm in front of it, and the fluid inside the eye, called the
aqueous humor, behind it. There is a generous supply of nerves inside the cornea. Thus,
injuries to the cornea can be quite painful.