Ikram Haq, who received a double cornea transplant, poses in a photo showing his love for boxing to mark the centenary of the world's first successful cornea transplant in 2005.

Rankin for UK Transplant via Getty Images

For two small organs sitting on our faces, our eyes are pretty smart. They can process 36,000 bits of information every hour and have 2 million working parts [source: Convery Optometrists]. Can other human organs like the gallbladder and the lungs top that? We don't think so.

Since the eyes play such a crucial role in what the brain processes, it's imperative that our vision is always at its peak. But sometimes, even the eyes -- more specifically the corneas -- fall short in that area, and cornea transplant surgery is needed. More than 40,000 cornea transplant surgeries are performed in the United States each year, according to the Foundation of the American Academy of Ophthalmology. Of all transplant surgeries done on a regular basis -- including heart, lung, and kidney -- cornea transplant surgery is not only the most common, but it's the most successful. Transplants are rarely rejected because the cornea has no blood supply so antibodies and immune cells cannot reach it [source: Medline Plus]

So exactly what is the cornea? It is our eye's outermost layer, the clear surface that covers the colored iris and the round pupil in a person's eye. The cornea has one specific purpose: to focus the light that comes into our eyes so we can see clearly. In order to do this effectively, our corneas must be clear and cloud-free.

Even though it's dome-shaped, the cornea is really nothing more than a group of cells and proteins. It's no bigger than a dime and no thicker than a credit card [source: University of Michigan Kellogg Eye Center].

But sometimes this "window" becomes injured, diseased or scarred. When this happens, the cornea begins to distort the light that enters it and a glare is produced. A person experiences blurred vision or even blindness. To correct the problem, an ophthalmologist might first suggest wearing eyeglasses or special contact lenses. She might even advise medication to alleviate any painful swelling. If these methods don't work, then cornea transplant surgery might just be the next step.

What circumstances make a person a good fit for corneal transplant surgery? If you're experiencing corneal failure after cataract surgery; have a scar resulting from an injury or poke in the eye; have a bacteria or fungus from a contact lens; or if your eye rejected a previous corneal transplant, you may qualify. Basically, if a person's vision cannot be corrected using non-surgical means, a transplant might be in order.

The next step is to search for a donor. Since almost anyone can donate their corneas after they die, there's not a long wait to receive one [source: Mayo Clinic]. When a healthy cornea is found, the donor will be tested for the AIDS and the hepatitis virus.

On the next page, we'll talk about the surgery and the recovery.