Corneal Transplantation
Corneal Transplantation for Corneal and External Eye Diseases
The cornea is the clear covering on the front of the eye which bends, or refracts, light rays that focus on the retina in the back of the eye. A certain shape or curvature is required in order for light to focus exactly on the retina, rather than in front of it or behind it.
An improperly curved cornea may be corrected surgically or non-invasively to reduce or eliminate the need for eyeglasses or contact lenses. A thorough eye examination and consultation are necessary before a treatment decision can be made.
Corneal transplantation, or keratoplasty, is recommended when the cornea's curvature is too steep or flat to be treated with other methods, or when extensive damage has occurred due to disease, infection or injury. Common problems that require transplantation are:
- Dry Eyes
- Blepharitis
- Recurrent Erosion
- Corneal Ulceration
- Herpes Simplex Keratopathy
- Pseudophakic Corneal Decompensation
- Keratoconus
- Corneal Dystrophies
- Pterygia
- External tumors
- Eye infections
- Traumatic injury
- Ocular surface diseases
- Chemical burn
Transplantation involves replacing the damaged cornea with a healthy one from a donor (usually through an eye bank). Keratoplasty is a low-risk procedure - it is the most common type of transplant surgery and has the highest success rate.
During the procedure, a circular incision is made in the cornea. A disc of tissue is removed and replaced with healthy tissue; these discs may be thin (lamellar keratoplasty) or as deep as the entire cornea (penetrating keratoplasty, the technique used in almost all corneal transplants). Local or general anesthesia may be used. The entire procedure lasts only 30-90 minutes.
DSAEK
DSAEK is the latest technique in corneal transplantation. Short for Descemet-stripping automated endothelial keratoplasty, DSAEK offers clear post-operative vision and short recovery time to patients in need of new corneas.
Patients are given topical anesthesia so they can't feel anything during the DSAEK procedure. First, the surgeon cuts and prepares the donor cornea. Next, he or she makes a mark in the surface of the patient's cornea with a trephine (an instrument used to cut circular sections of tissue). That mark serves two purposes: it helps the surgeon determine what size the transplant should be, and it outlines the area of the patient's cornea that needs to be peeled away.
Next, the surgeon scores the damaged section of the cornea and strips the membrane away from the eye using a microkeratome blade – the same instrument used in LASIK surgery. Then the donor cornea is folded into a "taco" shape and placed on the eye. A single stitch closes the incision.
Sometimes the new cornea unfolds on its own; other times, the surgeon unfolds it him/herself. When it is unfolded, a second stitch is made to close the wound and anchor the new cornea in place. The surgeon then injects an air bubble underneath the cornea, making sure it is centered on the eye, and dilates the pupil with eye drops.
Patients are sent to the recovery room for about one hour, after which they are examined at the slit lamp with the doctor. He or she gently presses on the cornea until most of the air bubble is released. Patients are then given antibiotics and steroid eye drops and will return the next day for a follow-up appointment. About 10% of patients need a second bubble injection to re-center the cornea.
Pterygium Treatment
Pterygium is a benign growth of the conjunctiva (lining of the white part of the eye) that grows into the cornea, which covers the iris (colored part of the eye). It can eventually lead to impaired vision.
Patients with pterygium often first notice the condition because of the appearance of a lesion on their eye or because of dry, itchy irritation. Other symptoms include dryness, redness, irritation, inflammation, and tearing. In more severe cases, the pterygium grows over the pupil and limits vision.
The most common pterygium treatment is eye drops (artificial tears) and use of sunglasses. In more severe cases when vision is impaired, surgery may be recommended.
