Answer: Corneal Tissue

The tissue of your cornea, the lens of your eye, is unique in the body in that it is the only living tissue that does not receive its nourishment directly from the blood vessels. Because transparency is a critical component of any lens, the cornea is instead nourished indirectly via nutrients delivered internally through the aqueous humor (the clear fluid inside the eyeball) and externally, via the tears.

What makes this unique tissue even more unique is that it receives its oxygen not by blood-borne delivery as is the case with the rest of the body but by absorbing the necessary oxygen directly from the air it is in contact with–the oxygen is dissolved in the tears and then diffused into the cornea.