Your cornea is like a clear window that breathes air instead of using blood. Because it stays away from your blood system, it is much easier to transplant without your body "fighting" it!
In a body full of thousands of miles of blood vessels, the cornea stands alone as a perfectly clear, "bloodless" zone. This crystal-clear layer at the front of your eye has a very special way of staying alive.
Blood is full of red cells that carry oxygen, but they are also opaque. If your cornea had blood vessels, your vision would be blurry and red! To stay perfectly transparent, the cornea evolved to be avascular (meaning no blood vessels).
Since it can't get oxygen from blood, the cornea gets most of its oxygen directly from the outside air. It dissolves oxygen into your tears, which then soak into the cornea. Nutrients are supplied by a clear fluid behind the eye called aqueous humor.
Because the cornea doesn't have blood flowing through it, it is "immunologically privileged." In regular organ transplants, your white blood cells (the "police" in your blood) quickly find and attack foreign organs. With the cornea, those "police" cells have no "roads" (vessels) to get there easily, making transplants very successful.
Your cornea is a biological masterpiece - a living tissue that functions like a piece of glass by breathing air instead of relying on blood.
