The cornea is the transparent, cone-shaped window covering the front of the eye. Most of the eye’s ability to focus comes from the power of the cornea. Most tissues in the body receive their nutrients through blood vessels; however, the cornea does not have any blood vessels so it receives nourishment from the tears and aqueous fluid (fluid in the back of the eye). Because the cornea has no blood vessels, it has a clear and shiny surface which must remain transparent in order to refract light properly. The cornea serves as a filter to screen out some of the damaging ultraviolet (UV) wavelengths in sunlight. This protection allows us to see images clearly in sunlight and prevents the eye from susceptibility to injury from the sun.
The cornea is composed of five different layers, each contributing to the overall health of the cornea and each having its own function. The most important layer is called the epithelium which is the outermost layer. This layer serves as a protective barrier to the harmful elements of the environment and as a barrier to the harmful UV rays of the sun. The smoothness and shape of the cornea is important to maintain in order for proper functioning. If either the surface smoothness or the clarity of the cornea is disturbed, vision becomes distorted.
There are various eye surgeries used to change the shape of the cornea so that the need for corrective lenses is reduced. Some common corneal conditions include: