Corneal Transplant

Corneal Transplant Surgery

What is the cornea?

The cornea is the clear, dome-shaped tissue covering the front of the eye. It is about the size of a dime and the thickness of a credit card. The cornea is kept moist and nourished by a thin layer of tears. It is kept smooth by the blinking of the eyelids. If the cornea becomes distorted in shape, scarred, or hazy (opaque) from disease or injury, the light rays passing through it are distorted and the vision is reduced. In some cases, a corneal transplant may be necessary to replace the diseased or injured cornea with a healthy, clear cornea to restore good vision.

What is Corneal Transplant Surgery?

In corneal transplant surgery the scarred or damaged cornea is removed and replaced by a human donor cornea called a graft. Corneal transplant surgery also is called penetrating keratoplasty or corneal grafting. Your eye is the recipient eye because it receives the graft. The other person’s cornea is the donor cornea or donor tissue because the cornea is being donated or given to you.

The Donor Cornea

An eye bank provides the donor tissue for corneal transplant surgery. The corneas are obtained from deceased individuals who arranged for donation prior to their death or whose families gave permission. Many eye banks are supported by Gift of Sight Ambassadors, volunteer groups composed of corneal transplant recipients and family members of eye tissue donors. These ambassadors help increase awareness about eye tissue donation and corneal transplantation by sharing their personal experiences as well as describing the difference the procedure has made in their lives.

The normal cornea does not have any blood vessels. It is thought that this lack of blood vessels may prevent the body from recognizing the “foreign” donor cornea. Ongoing research studies in compatibility testing between donor and recipient may lead to ways of increasing the chance of a successful outcome in situations with higher risk of transplant rejection.

Race, sex, blood type, eye color, and near- and farsightedness are not considered in selecting the donor because they do not affect the outcome of the corneal transplant surgery. Donor corneas can be safely stored in refrigerated fluid for several days, improving the chances of successful surgery and allowing for better planning and timing of surgery.

The Surgery

Corneal transplants are performed on an outpatient basis under general anesthesia. The surgeon performs the surgery while looking at the eye through a microscope. A cookie cutter-like knife called a trephine is used to cut and remove a circular piece from the recipient’s scarred cornea. A similar knife is used to cut and remove a piece from the donor cornea. The donor cornea then is placed where the recipient’s cornea was removed. It is sewn into place with very fine sutures which are smaller in diameter than a human hair.

In some situations, your surgeon may be transplanting only part of the corneal thickness. When only the front part is transplanted, it is called anterior lamellar keratoplasty. When only the back part is transplanted, it is called endothelial keratoplasty. Some variations of endothelial keratoplasty include DSEK (Descemet’s stripping endothelial keratoplasty) and DMEK (Descemet’s membrane endothelial keratoplasty).

After the Surgery

Eventually, most of the donor tissue is replaced by your own cells. Because of the cornea’s lack of blood supply, healing takes place very slowly. You will be asked to wear your eye shield for a few weeks. Sutures may not be removed for months. They are removed easily in the office. Restoration of vision after corneal transplant surgery is gradual. The vision in the operated eye will be somewhat blurred and distorted until final glasses or contact lenses are prescribed.

There are things you can do to help insure the success of the surgery. It is especially important to avoid situations in which you might sustain a blow to the operated eye. This could damage or loosen the new cornea. In addition, you will need to use eye medications for many months or years and have regular check-ups with your ophthalmologist. Failure to follow the schedules for medications and examinations could greatly decrease the chance of a successful surgery.

The next few paragraphs will describe some problems that could delay or prevent the return of useful sight in your operated eye. There is a good chance for successful treatment of these problems if they are treated early.

Graft Rejection

There always is a possibility that the body will reject the graft. This is like an “allergic” reaction of the body against the donor cornea. It can occur any time after the surgery. There is a good chance this can be treated successfully if you act immediately. There are four danger signs you must know. If any of these occur and last for more than 12 hours, you should call your ophthalmologist – even if it is a weekend or a holiday.

Signs of Graft Rejection

To remember the signs of graft rejection, remember the letters RSVP:

• Redness
• Sensitivity to light
• Vision changes
• Pain

Make a habit of checking your eye every day. Check your vision at about the same time and in the same lighting each day, perhaps at the same time you do another routine activity, such as brushing your teeth.

Redness

For a few weeks after surgery, your eye may be red. If at any time your eye begins to get redder, you should call your ophthalmologist. You easily can check the redness of your eye by looking into a mirror and pulling down the lower lid. Look carefully at the white part of the eye, especially in the area next to the cornea.

Sensitivity to light

Bright lights may seem irritating to your eye after surgery. This, too, slowly should get better. If you notice your eye becoming so sensitive to light that you feel like covering it, you should call your ophthalmologist.

Vision changes

Your vision most likely will improve gradually after your surgery. Make a habit of checking your vision every day. Check it at about the same time and in the same light. Pick an object in your house that has some pattern or detail to it. Look at the object with your operated eye while covering the other eye with your hand. If your vision seems to be getting worse, you should call your ophthalmologist.

Pain

It is normal to have occasional small twinges of pain in your eye. If your eye develops constant pain or dull aching, you should call your ophthalmologist.

Other Problems that May Occur

Wound separation

A small gap may occur in the area where the edge of the graft is sewn into the eye. You may have no symptoms at all or you may feel a dull ache. The wound separation might be treated with a patch or a soft contact lens. It is possible the graft may require additional suturing in the operating room.

Loose or broken suture

Occasionally, a suture can loosen or break during the healing process. This may cause a “gritty” foreign body sensation, especially when you blink. The loose suture can be removed easily in the office.

Astigmatism

This occurs when the grafted cornea has an oblong or irregular shape rather than a round shape. All grafts have some astigmatism and this usually can be corrected with glasses or contact lenses. If the astigmatism is severe, a special kind of surgery often can correct it.

Refrence: www.umkelloggeye.org

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