Corneal transplantation is the second-most common transplant procedure.
The dome-shaped cornea is often described as an eye's watch crystal. It covers the front of the eye, and is normally transparent. The cornea bends and focuses light rays onto the eye's lens, which refocuses light onto the retina. According to Joel Sugar, MD, director of the cornea service at the University of Illinois at Chicago Department of Ophthalmology, about 40,000 cornea transplants are performed in the United States annually. An ongoing study suggests a possible benefit for blood type matching , but right now most eye banks and surgeons don't tissue or blood match cornea donors and recipients.