The human eye is one of the more complex organs of the human body and features some characteristics that are totally unique. The eye itself consists of a number of components and is responsible for light perception, vision and depth perception. It does all this by focusing light from the outside world through the cornea and onto the retina at the back of the eye.
For one's vision to be clear, the cornea needs to be totally transparent—so much so that it can not even contain any blood vessels. Nevertheless, he cornea is still made up of living cells and they need oxygen and nutrients to survive.
The cornea therefore takes its oxygen directly from the air. It does this by first having the oxygen absorbed by the tears, from where the cornea extract it. Nutrients are also supplied to the cornea via the tears through the process of diffusion.
So, next time somebody finds you crying, just tell them you are feeding your cornea.