Corneas Have No Blood Vessels

The eye's transparent outer window performs a remarkable biological balancing act. As living tissue, the cornea requires a constant supply of oxygen and nutrients to survive, yet it must remain perfectly clear to focus light onto the retina. To solve this evolutionary puzzle, it forgoes a traditional blood supply entirely. Instead, it uniquely "breathes" oxygen directly from the atmosphere every time our eyes are open and absorbs vital nutrients from the tear film on its surface and the aqueous humor fluid from within the eye. This elegant solution is absolutely critical for vision, as the presence of even microscopic blood vessels would scatter light and render our sight a blurry, indistinct mess.

This avascular nature has a fascinating and medically significant consequence: it creates a state of "immune privilege." Because the body's immune cells primarily travel through the bloodstream to patrol for foreign invaders, the cornea is effectively shielded from the body's main defense systems. This is a primary reason why corneal transplants have one of the highest success rates of any transplant procedure. Without blood vessels acting as highways for immune cells, the risk of the recipient's body identifying and rejecting the donor tissue is dramatically reduced, allowing surgeons to restore sight with remarkable consistency.