What is corneal transplantation?
Corneal transplantation (also called Keratoplasty or corneal graft transplant) is preformed to restore or significantly improve the visual function. It involves the removal of damaged or scarred cornea (due to a disease or an eye injury) and replacing it with a healthy donor cornea. This surgery can involve the replacement of the entire cornea (total keratoplasty) or only a portion of the cornea (partial keratoplasty).
What happens before surgery?
After establishing candidacy for corneal transplantation surgery, the patient is listed at a local eye bank. It may take some time to find suitable tissue from a donor eye for the corneal transplantation surgery and to perform standard screening to ensure that the donor cornea is healthy and free from diseases like hepatitis and AIDS.
What are the techniques used for keratoplasty?
The difference between the techniques of the keratoplasty in surgery is the size and structure of cornea replaced.
It is the traditional technique of keratoplasty which involves the replacement of the whole thickness of the cornea.
Lamellar keratoplasty is preformed by several techniques all involving the selective replacement of the diseased layers of the cornea, while the healthy tissue is left intact. It produces a reduced optical performance and is more technically challenging. However, it has major advantages over penetrating keratoplasty. For instance, lamellar keratoplasty involves a faster and better recovery as the corneal graft is quickly rehabilitated. In addition the structural integrity of the eye is more intact.
1- Deep anterior lamellar keratoplasty
This type of lamellar keratoplasty involves the removal and replacement of the anterior layers of the central cornea. This technique is useful in treating anterior corneal opacities, scars, and keratoconus (bulging of an abnormally cone-shaped cornea).
2- Endothelial keratoplasty
The cornea comprises of several layers, the outer surface of the cornea is called epithelium while the inner surface is called the endothelium. The corneal endothelium controls the fluid balance in the cornea. So an endothelial dysfunction can result in corneal swelling and loss of vision. Endothelial keratoplasty (EK) is the replacement of the corneal endothelium with a disc of posterior stroma, Descemet’s membrane and endothelium (DSEK) or Descemet’s membrane and endothelium (DMEK) with no stroma. DSEK is the most common type of EK. During both types of endothelial keratoplasty, the surgeon will:
- Implant healthy donor tissue that was already prepared before surgery
- Make a tiny incision and remove the diseased corneal endothelium.
- Then, hold the position of the new endothelial layer by injecting air bubbles in the anterior chamber immediately post-implantation. After the tissue adheres the air is adsorbed into surrounding tissue.
- Finally, close the incision by a suture or two at the end of the surgery. However some times the incision is self-sealing and no sutures are needed.
What are the advantages and disadvantages of endothelial keratoplasty?
When comparing endothelium keratoplasty with traditional penetrating keratoplasty, endothelial keratoplasty has the following advantages:
- The structural integrity of the eye is kept intact (which makes the eye resistant to injury after surgery).
- Faster visual recovery is achieved as the recovery may take few days compared to years with the penetrating corneal transplantation surgery.
- Minimal activity limitations are needed after surgery.
What can you do to recover safely?
Recovery from the corneal transplantation surgery can take up to a year or longer. While the patient’s eye is adapting to the new cornea, vision might be blurry or even worse than before surgery in some cases. It is important to follow the surgeon’s instructions to ensure a safe and fast recovery with decreased chance of complications. The patient will be given instructions about:
1. Activity after surgery
As the patient’s vision improves, he/she will be able to resume daily activities. However, any strenuous activity (heavy exercise and lifting) should be restricted for weeks after surgery until the patient recovers completely.
2. Medications and treatments after surgery
Patients should comply with the prescribed steroid eye drops to help the body accept the corneal graft and other medications to control infection, discomfort and swelling. Patients are also advised to wear the eye shield at all times to protect their eyes from impacts or debris entering the eye.
3. Removal of the stitches
The stitches made to hold the new cornea in place are removed by the ophthalmologist usually after 3 to 17 months depending on the health of the eye and the healing rate. The ophthalmologist can readjust the sutures surrounding the implanted corneal graft to help lessen the extent of astigmatism that result from an uneven eye surface.
4.Early detection of graft rejection
Patients should contact their doctor immediately if they experience Redness, extreme Sensitivity to light, decreased Vision, Pain (acronym: RSVP). These specific symptoms are the warning signs of the most serious complication of corneal transplantation surgery: graft rejection.
What is the effect of surgery on the patient’s vision?
Because the new cornea cannot exactly match the curve of the patient’s natural cornea, the vision will fluctuate for several months after surgery. Patients are left with a degree of nearsightedness (myopia) and distorted images defect (astigmatism).These errors of refraction are unpredictable, but they can be corrected with LASIK eye surgery, corrective glasses or contact lenses. It is important that the patient wait until vision is stabilized before filling eyeglass or contact lens prescription or undergoing LASIK or PRK surgery.