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The front covering of our eyes is called the cornea. It is an incredible example of complex design. The material of which the cornea is made has to be perfectly clear to allow light to pass through it so that we can see. Because of the need for complete transparency there are no blood vessels in the cornea. It is the only part of the human body that has no blood supply. It gets its nourishment from the aqueous humor (the liquid inside the eye) and the tear fluid on the outside and it gets oxygen from the air.
However, there is a problem with the cornea being exposed to the air with all of the contaminants it contains – pollen, dust, chemicals, grit. The cornea also has to be able to withstand blows and fit to a curving surface full of a fluid which maintains the pressure of the eye.
Over time any surface exposed to dust and grit and sometimes bumps and blows can get tiny scratches in it. How is it possible that the cornea remains clear? How can it get scratched and heal without obstructing our vision?
If you cut your skin, the cut heals from the bottom up. Because of that, scar tissue is formed. According to Marty Gilliam a mechanical engineer from Athens, Alabama, the cornea of the eye is different. When the corneal epithelium, the outer layer of the cornea, gets scratched, the cells of the separated walls move toward one another, and close the scratch so that no scar tissue is formed.
If scar tissue formed every time the surface of our corneas got scratched, by the time we reached middle-age we would be looking through cloudy lenses. If you can read this, you should be thankful for another Dandy Design!
References-
“cornea,” Wikipedia
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