What is the cornea and why is it important?
The cornea, the outermost layer of the eye, protects the eye from dirt and germs and plays an important role in vision. As light enters the eye, the cornea bends it to help you focus on distant or nearby objects.
When the cornea is damaged due to infection, injury, or disease, the resulting scars can negatively impact your vision. These scars may block or distort light as it enters the eye, impairing your ability to focus your vision.
Symptoms of corneal problems include pain, tearing, blurred vision, redness, and light sensitivity. Corneal damage may occur due to injury, infection, or underlying disease. Some people have a genetic predisposition to corneal issues.
Keratoconus is a condition that causes the cornea to bulge outward like a cone. This occurs when the collagen fibers that hold the cornea in place weaken over time. The collagen weakens when levels of protective antioxidants in the cornea are low.
Keratoconus tends to run in families. Certain medical conditions, including some allergies, also increase one’s risk.
Symptoms of keratoconus include blurred vision, seeing streaks of light, difficulty seeing in bright light, and seeing halos at night. In severe cases, scarring can occur and damage the cornea.
This damage can make it impossible to focus one’s vision without glasses or contact lenses. In severe cases, corneal transplant surgery may be needed to restore one’s vision.
When is surgery needed?
Corneal transplant surgery may be necessary if infections, scarring, and inherited or degenerative conditions have damaged the cornea and negatively impacted one’s vision.
Before surgery, a doctor will perform a complete eye exam, measure the eye to determine the size of the required donor cornea, review the patient’s current medications, and address addition eye problems.
Corneal Replacement Surgery
During corneal transplant surgery, the center of the cornea is removed and replaced with a donor cornea. Depending on the extent of corneal damage, a doctor might choose to replace the entire cornea or only one section.
Most donor corneas come from deceased donors. Patients typically do not need to wait long for a donor cornea to be found.
During the procedure, a local or general anesthetic may be used. A surgeon uses an instrument known as a trephine to remove a round section of the cornea from both the patient and the donor. The patient’s cornea is then removed and replaced with the donor cornea. The donor cornea is stitched in place with small sutures using a microscope.
Different Forms of Surgery
During a penetrating cornea transplant, all five layers of the cornea are replaced. During a lamellar cornea transplant, only some layers are replaced.
Lamellar cornea transplants can be anterior or posterior depending on which layers are transplanted. An anterior lamellar corneal transplant involves replacing the layers closest to the surface of the cornea. A posterior lamellar corneal transplant involves replacing deeper layers of the cornea.
A successful corneal transplant improves the appearance of a damaged cornea, reduces pain, and improves vision. A doctor may make adjustments when the outer layer of the cornea has healed several weeks or months after the surgery. These corrections might include tightening or loosening the stitches to correct unevenness on the cornea or correcting nearsightedness or farsightedness caused by issues with refraction.