Corneal transplantation is a surgical procedure, where the damaged cornea of the patient is replaced with a healthy cornea from a donor. The donor is invariably a person who has just passed away and has agreed to donate his/her eyes. The cornea is first checked for surgical use before the procedure. Blood type, race, gender, far-sightedness or near-sightedness do not affect the selection of the cornea for the surgery. During the procedure, the patient is given local anesthesia that prevents the movement of the eye muscles and reduces the pain from the procedure.
Who Can Be a Corneal Tissue Donor?
The cornea for the surgery is obtained from individuals who have given their consent to donate their eyes after their lifetime. Eye donation organizations or eye banks get support from volunteers. The cornea is checked for any diseases and for its clarity before being provided for the surgery. In India, eye donations have increased with the development of the Hospital Cornea Recovery Programs (HCRP). This has enabled trained eye consultants to approach potential families to become eye donors. Obtaining consent through the right kind of information has increased eye donations in India that is struggling to meet the need of corneas for transplants.
Types of Corneal Transplants
There are 3 types of corneal transplants:Lamellar keratoplasty:
In lamellar keratoplasty, the outer or inner layer of the cornea is removed and replaced with a new donor tissue.
This procedure minimizes complications and the rate of recovery is faster. When the outer layer is transplanted, the procedure is called anterior lamellar keratoplasty, and when the inner layer is transplanted, the procedure is called endothelial lamellar keratoplasty.Penetrating keratoplasty:
In this procedure, a piece of the cornea is removed and replaced with a healthy cornea from a donor. In this procedure, the recovery takes 6 to 12 months for the vision to become normal. The stitches take nearly a year to heal and there is a risk of complications to the new cornea. Femtosecond laser technique:
Dr. Roger Steinert from the University of California, Irvine developed this technique. This procedure has revolutionized corneal transplant surgery, since lasers are focussed at the selected depth to cut and remove the damaged tissue. The laser is able to remove the damaged tissue without causing injury to the surrounding tissue. Based on the shape of the excised portion of the donor cornea, the surgeon can make a similar cut that will allow an exact fit of the donor tissue. The exact incision results in a better recovery of the individual, easy removal of the stitches, and fewer complications.
Corneal Transplantation Surgical Procedure
The corneal transplantation surgery
is an outpatient technique that requires local anesthesia. Prior to the surgery, patients should stop taking blood-thinning medications; these medications can be stopped 10 days prior to the surgery. The night before the surgery, individuals should abstain from drinking fluids or eating solids after midnight. Water, coffee, apple juice, and tea are sometimes allowed before the surgery. The surgeon uses a microscope to observe the eye and perform the surgery. A knife, called the trephine, is used to cut out the damaged cornea. A similar knife is used to remove the donor cornea and insert it into the host tissue. The inserted cornea is stitched in with the host bed tissue using fine sutures. Certain exceptions such as Descemetís stripping endothelial keratoplasty (DSEK) and deep lamellar endothelial keratoplasty (DLEK) do not require sutures. The corneal transplantation surgery takes a total time of 1 to 2 hours, which includes preparing the patient for surgery.
Recovery from a corneal transplant
The healing time in the case of standard penetrating keratoplasty takes nearly a year. In the course of time, the host tissue replaces the donor tissue. Due to the absence of blood vessels in the cornea, it takes a longer time to heal and the sutures are removed after a year. Patients are advised to wear a protective cover for the eye for a few weeks following the surgery. Vision is restored gradually over 6 to 8 months though it is blurred. It is corrected with contact lenses or glasses. Medications for the eye are prescribed and regular checkups with the ophthalmologist are advised. The patient must avoid situations (blows or scratched) that can cause damage to the eye following the surgery.
Risks associated with corneal transplantation
Some of the risks involved with corneal transplantation include the following:
- Scars in the eye
- Vision loss
- Corneal swelling
One in 3 patients display a risk where the cornea is rejected. This occurs in the first 5 years and may be controlled with the use of steroid eye drops. Despite the fact that the cornea does not have a blood supply, it faces rejection by the host eye. Sometimes the rejection occurs after many years. The exact reasons for the rejection are not understood.
There are 4 main symptoms that indicate the graft is being rejected. The individual should immediately get checked if the symptoms persist for more then 12 hours. The symptoms are as follows:
- Redness in the eye
- Problems in vision
Corneal transplant takers advantage of the property of immune privilege. Several factors in the cornea prevent it from being rejected, thus improving the chances of the graft being accepted. It has however been suggested that high-risk patients for transplant rejection would benefit from matching the human leukocyte antigens (HLA) with those in the donor tissue. Matching HLA antigens between the donor and the host may lead to very low chances of rejection.
Currently, patients are recommended to get artificial corneas
(keratoprostheses) transplanted in the event of a rejection. However, there is no clear evidence of the benefit of artificial corneal devices (eg, Boston type 1 keratoprosthesis, Miro Cornea“, Osteo-odontokeratoprosthesis, KeraKlear“) over donor corneal transplants.
Individuals should take precautions to avoid any damage to the operated eye (eg, blows or cuts.2.
Individuals should avoid driving soon after surgery. They should be prepared to go home with a family member or a friend.3.
Cover the eye while bathing or sleeping. 4.
The recovery rate of individuals varies. Hence, individuals can return to their normal activities based on the level of recovery of the eye. Those, who do not feel comfortable with their vision, may take longer to return to work.