What is Cornea Transplant Surgery?
Cornea transplant surgery, also known as keratoplasty, is an operation to replace a portion of a cornea with corneal tissue from a donor. A cornea transplant can restore vision, decrease pain, and enhance the appearance of diseased or injured corneal tissue. Read about diseases of the cornea.
The cornea is the most exterior layer of the eye. It is the transparent, dome-shaped outer layer that shields the front of the eye and plays a significant role in the visual acuity of the eye. The cornea is the clear layer that overlays the iris and pupil in the front of the eye, and corneal tissue is made up of five layers: epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. Containing a distinctly organized set of proteins and cells, the cornea serves as a protective layer of the eye.
The cornea functions to screen the eye from germs, dust, and other detrimental matter. It also serves as the entry point for light into the eye by refracting light incoming light into the lens of the eye, similarly to the way a camera takes a picture. In simpler terms, the cornea is responsible for a large portion of the eye’s power to focus.
Why Have Cornea Transplant Surgery?
A cornea transplant is most frequently used to reestablish the vision of a person with a damaged cornea. The eye can become seriously injured by a multitude of problems including:
- Chemical and thermal injuries.
- Chronic infections (corneal ulcers) or inflammation.
- Neurotrophic conditions (due to injury to the eye’s nerves or poor lid closure due to injury to the nerves).
- Pathological diseases like pemphigoid and Stevens-Johnson syndrome.
- New tissue growths like pterygium (speculated to be related to sun damage).
The aforementioned problems cause substantial injury to the surface of the eye, which leads to scarring and the formation of new blood vessels. This damage precipitates loss of vision.
As mentioned, cornea transplant surgery may also reduce pain or improve the appearance of a diseased or damage cornea. A doctor may recommend cornea transplant surgery to treat a number of other conditions including:
- Thinning of the cornea.
- Clouding of the cornea
- Swelling of the cornea
- Outwardly bulging cornea (keratoconus).
- Scarring of the cornea (caused by injury or injection)
- Fuchs’ dystrophy
- Corneal ulcers (including those due to infection)
- Complications due to prior eye surgery
Risks and Complications of Cornea Transplant Surgery
Cornea transplant surgery is considered a reasonable safe procedure, but there is a small risk of severe complications including:
- Increased risk of clouding the lens of the eye (cataracts)
- Increased pressure within the eye (glaucoma)
- Swelling of the cornea
- Eye infection
- Complications with the stitches used to fasten the donor cornea
- Rejection of the donor cornea
In particular, rejection of the donor cornea is a very serious possible complication of a cornea transplant operation. Rejection occurs in about twenty percent of cornea transplant patients. Rejection means the body’s immune system inadvertently attacks the donor tissue, because it recognizes it as foreign rather than accepting it. Rejection of donor cornea tissue may necessitate another cornea transplant or medical treatment. A doctor should be contacted if a patient suspects any signs or symptoms of transplant rejection including:
- Loss of vision
- Sensitivity to light
What to Expect Before Cornea Transplant Surgery
Before Cornea transplant surgery a doctor will perform a thorough eye exam and check for any conditions that could cause problems after surgery. The doctor will measure the patient’s eye to decide the size donor cornea the patient needs. Before surgery, the patient may need to stop taking particular medications or supplements, and the doctor will inform the patient of requirements concerning medications after reviewing all medications or supplements the patient is taking. Also, prior to surgery, a doctor will treat any other eye problem that may exist. Separate eye problems like infection or inflammation can potentially reduce the success of a cornea transplant, so a doctor will treat any of these issues before surgery. Finally, the doctor will inform the patient of any risks associated with the procedure and what to expect during the surgery.
The majority of corneas used for cornea transplant surgery come from deceased donors. Finding a donor does not typically take a long amount of time, because a large amount of people specifically request that their corneas be donated after they die.
What to Expect During Cornea Transplant Surgery
The patient will be administered a sedative on the day or cornea transplant surgery to help them relax. Local anesthesia is used to numb the eye, so the patient will be awake for the surgery but will not be any pain.
Full thickness cornea transplant (penetrating keratoplasty)
This is the most commonly performed type of cornea transplant surgery. The surgeon cuts through the complete depth of the diseased or abnormal cornea and removes a disc of corneal tissue comparable in size to a button. An instrument called a trephine, which looks like a cookie cutter is used for this specific circular incision. After being cut to fit, the donor cornea is put in the opening, and the surgeon stitches the new cornea into place with a fine thread. At a later visit, these stitches may be removed.
Partial thickness (lamellar) cornea transplant—There are two types of lamellar cornea transplants:
Replacing the innermost corneal layer—For this type of cornea transplant surgery, a surgeon replaces the inner layer of the cornea. This procedure is called a deep lamellar transplant, and of the cornea’s five layers, replaces only the innermost layer. The surgeon makes a small incision makes a small cut in the side of the eyeball to remove the innermost layer of the cornea without injuring the other four layers. The surgeon then replaces the innermost portion with a donor graft.
Replacing the surface corneal layers—For this type of cornea transplant, a surgeon replaces the outer layers of the cornea that have been injured by conditions or particular diseases. This procedure is called a surface lamellar transplant, and during this operation, the surgeon replaces the outer layers of the cornea with a portion of a donor graft.
What to Expect After Cornea Transplant Surgery
After a cornea transplant surgery, the doctor will prescribe several medications for a patient to take including eye drops, and sometimes, oral medications to help manage infection, pain, and swelling. The patient will wear an eye patch to shield the eye, while it heals and protect it from any injury. The patient will need to refrain from any strenuous activity after surgery and slowly return to normal activities, including exercise. The patient will, in general and for the rest of their life, need to take extra precautions to avoid injuring their eye. The patient will also return to their doctor for continual follow-up exams, and during the first year following cornea transplant surgery, the patient should anticipate frequent eye exams, during which the doctor will check for any post surgery complications.