The cornea is the normal clear window over the colored part of your eye (iris). When the cornea is diseased, it loses its clarity or shape and compromises your vison. A variety of conditions can lead to needing a transplant.
A corneal transplant involves having surgery to replace your cornea with a cornea that has been donated by someone who died. The cornea you will receive is referred to as the donor cornea, and it will be provided by a licensed and certified eye bank. Because the cornea does not have a direct blood supply, you do not have to be matched to your donor. This is also advantageous that you do not have to suppress your body’s immune system with pills. You will however, need to suppress the eye’s immune system with steroid drops. You will likely be on a steroid drop for the rest of your life after your transplant.
Traditional corneal transplants are full thickness – or remove the entire cornea. Some patients are candidates for a partial thickness transplant (DSAEK). Your doctor will inform you of their opinion. Both types of surgery are performed on an outpatient basis either under sedation and local anesthesia or under general anesthesia.
Partial Thickness Cornea Transplant (DSAEK)
DSAEK (Descemet’s Stripping Automated Endothelial Keratoplasty) replaces only the innermost layer of cells within the cornea, known as the endothelium. The endothelium has a very important function of “pumping” fluid out of the cornea and keeping its clarity. If the endothelium is not functioning properly then the cornea swells and loses its clarity. If this is the only portion of your cornea that is diseased, then you may be a candidate for DSAEK. This procedure is performed through a much smaller incision with shorter recovery time and fewer risks than a traditional corneal transplant.
During the procedure, the surgeon removes only the diseased endothelial cells. The donor tissue is cut specially to replace these cells and sized appropriately for your eye. It is then carefully folded, inserted into the eye and positioned, and the surgeon injects an air bubble underneath the cornea. The air bubble allows for adherence of the new transplant. A few stitches are placed to close the incision. These are buried and do not usually ever need to be removed.
After surgery, it is important that you remain positioned supine (flat on your back) as much as possible for the first 48 hours. This gives the air bubble sufficient time to allow the new donor cornea to attach properly.
Full Thickness Cornea Transplant (Penetrating Keratoplasty)
A full thickness cornea transplant, also known as a Penetrating Keratoplasty, is a surgical form of corneal transplantation that removes the entire cornea (all layers) and a new donor cornea is used for replacement. This type of transplant is indicated for those patients that have diseases or scars that affect all layers of the cornea or have corneas that are severely abnormally shaped. The new cornea is stitched into place, and the stitches are slowly removed after 6 months. It may take 12-18 months for vision to be restored to satisfactory levels. Many patients still require glasses or contact lenses after this procedure, but it may be the only option to restore vision in severe corneal disease.
A pterygium is a growth of fleshy tissue starting on the conjunctiva (white part of the eye) but extending onto the cornea. It can occur on both sides of the eye, but is more common on the side towards the nose. This growth may remain small and without any symptoms or may grow large enough to interfere with vision or cause irritation. Because these growths extend onto the cornea, they can change the shape of the cornea and cause astigmatism.
For patients with severe cases whose vision has been affected, different types of surgery are available. Surgery is the only way to definitively remove a pterygium, but it is not a perfect solution; it requires follow-up, and there is a small risk that the pterygium will grow back. Your surgeon will use the latest surgical techniques to minimize the risk of the pterygium coming back. Surgery is performed under local anesthesia on an outpatient basis. The two most commonly used surgical techniques involve either:
- Amniotic membrane transplantation: the pterygium is removed and the donor amniotic membrane (inner layer of the placenta) tissue is used to cover the area where the pterygium was excised. This type of graft encourages healing and reduces swelling. It is generally recommended in primary (first time removal of the pterygium) as well as recurrent cases.
- Conjunctival autografting: the pterygium is removed and then donor tissue is harvested from an area of healthy conjunctival tissue of your eye to cover the area where the pterygium was excised.
A superficial keratectomy is the removal of the corneal epithelium (outermost layer) down to the Bowman’s layer (basement membrane that holds the epithelium in place). The goal of a superficial keratectomy is to decrease irritation/inflammation, achieve a normal, smooth ocular surface, improve any decrease in vision, and prevent regrowth, if possible. Conditions resulting in the need for a superficial keratectomy include:
- Anterior Basement Membrane Dystrophy: abnormal maturation of the epithelial cells and basement membrane. These abnormal cells create an irregular corneal surface which can be comprised of parallel lines, white putty-like deposits, and fine haze or scarring. This condition is sometimes also called epithelial basement membrane dystrophy or map dot fingerprint dystrophy.
- Salzmann’s Nodular Degeneration: irregular white to bluish-grey opacities on the cornea that may cause foreign body sensation, visual disturbances, or irregular astigmatism
- Recurrent Erosion Syndrome: a recurrent condition that occurs when the epithelium does not stay attached correctly to the Bowman’s layer, resulting in pain, blurred vision, light sensitivity, and tearing. Sometimes additional procedures such as stromal puncture or diamond burr can also be performed.
After the procedure, a bandage contact lens is placed on the eye to reduce discomfort and promote healing. Patients are usually treated with antibiotic eye drops to reduce the risk of infection and anti-inflammatory drops to reduce post-operative pain and inflammation.