Penetrating keratoplasty is one of the surgical procedures that ophthalmologists can use to replace a damaged cornea. It replaces the entire cornea, unlike other procedures, which only replace the back layer of the cornea. Here's what you need to know about this procedure.

How do corneas become damaged?

There are many ways that your corneas can become damaged. Injuries to your eyes, like scratches or abrasions, or infections such as keratitis can lead to scarring on your cornea. Scars on your cornea lead to distorted vision, and serious scars can block much of the light from passing through your cornea.

Your corneas can also be damaged during eye surgeries, like the type that are used to correct your vision or remove cataracts. When this happens, your corneas will need to be replaced.

What do ophthalmologists replace your cornea with?

Ophthalmologists have a couple of different options when it comes to replacing your cornea. Their first option is to get donated corneas from an eye bank. Eye banks collect corneas from recently diseased people who had signed up to be organ donors, and then they evaluate them to make sure that they're good quality and free of disease. Eye banks have no shortage of corneas, and they provide about 70,000 corneas every year in America.

Your corneas can also be replaced with artificial materials. Artificial corneas have been developed out of polymer materials, and they function similarly to real corneal tissue.

How is penetrating keratoplasty performed?

First, an ophthalmologist will put antibiotic eye drops in your eyes to help prevent infection after the procedure, as well as drops to protect the lens of your eye and keep you from moving your eye. Next, you'll receive anesthesia. Local anesthesia is usually used for this procedure, which means that you'll be awake and aware of what's going on, but if you're very nervous, you can get general anesthesia and sleep through the procedure.  

Once your eye has been prepared and numbed, the ophthalmologist will get to work. He or she will trim the donor cornea to an appropriate size, then set it aside. Using a microscope, he or she will carefully remove your damaged cornea with tiny corneal scissors. The microscope is necessary to ensure that nearby tissues like the lens or the iris aren't accidentally cut. Then the donor cornea will be positioned on your eye and sewn in place with nylon stitches. The stitches are rotated slightly to hide the knots underneath your cornea, and then the procedure is finished.

Will this procedure improve your vision?

Penetrating keratoplasty usually causes major improvements in a patient's vision, but your vision may not be perfect. One study followed a group of people both before and after they had penetrating keratoplasty performed to find out how much the surgery improved their vision. 56.3% of these patients had vision of 20/200 or worse before the procedure, which is considered legally blind. After the procedure, only 3.8% of the study's patients had 20/200 vision.

Do donor corneas ever fail?

Donor corneas can fail, but this is a very rare occurrence. Studies have shown that this only happens to about 1.9% of people who undergo penetrating keratoplasty. Rejection of the donor tissue is a bit more common, affecting about 6.8% of patients, but this can be managed if it's caught in time. After five years, 97.6% of penetrating keratoplasty patients will still have their donor cornea in place.

Penetrating keratoplasty is a surgical procedure that replaces the entire cornea, and it's very effective. If you have damaged corneas due to an injury, infection, or a previous eye surgery, ask your optometrist if you are a good candidate for penetrating keratoplasty.