Q: When is a corneal transplant necessary?

A:A corneal replacement is done when damage to the cornea causes a drop in vision, or pain that interferes with daily activities such as driving, reading or working at a computer.

The cornea may become distorted by a variety of diseases, or scarred from infections or injuries. Some corneal conditions cause pain. Some people have corneal conditions that never need treating, while others require treatment early. If a corneal infection does not respond to medical treatment, a transplant may be needed to remove the affected tissue and replace it with healthy donated tissue.

The role of the Eye Bank

Fortunately, there is usually a cornea available when it is needed. The Eye Bank of Canada (originally launched as joint effort of CNIB and the Canadian Ophthalmological Society) receives donations from generous people who give the gift of sight by donating their eyes after they die. These donations are examined to ensure that the cornea is healthy, and suitable to be used for corneal transplant.

Outpatient surgery

Corneal transplant surgery is done on an outpatient basis. The operation takes about 45 - 60 minutes. During the surgery, you will be given a mild anaesthetic to help you stay relaxed, and some freezing around the eye area to keep it still and reduce discomfort. Your other eye will be covered, and a bright light shines into the eye being operated on, so you will see very little during the surgery.

There will be some tiny stitches about half the size of a human hair used to hold the new cornea in place. Patients typically do not feel these after a few days, and they usually stay in place for one year, after which they are removed in the ophthalmologist's office.

Donated tissue closely inspected

No tissue is used for corneal transplants until it has been inspected at the Eye Bank and found to be healthy. The tissue is tested before release for use in the manner prescribed by the Eye Bank Association of America (EBAA). Currently it must be tested negative for AIDS, and hepatitis B and C before it can be used for transplants.

Because human tissue is used, there is the remote possibility that the tissue may transmit diseases for which there is no screening test, or which are currently unknown. The good news is that the piece of cornea used for the transplant is tiny, so any exposure to disease will be minute.

Other procedures during transplant

If the patient has a cataract present or starting, it may be removed at the time of the corneal transplant. If it is not removed, the surgery and drops used after surgery may make the cataract worse. Usually an intraocular lens implant is placed at the same time that the cataract is removed.

If a person has an older-style intraocular lens implant, it may be replaced with a current model at the time of surgery. This prevents a continuation of any damage the old lens may have caused. The jelly, or vitreous, in the eye may have to be partially removed so it does not interfere with the healing of the corneal transplant. The space created by the removal of the vitreous is replaced with the normal watery fluid (aqueous humour) of the eye.

If there is other damage to the eye, an attempt will be made to repair it as much as is safely possible.

Recovery

After the surgery, a sterile dressing will be placed over the eye, along with a rigid protective shield that is left on until the doctor removes it the following day.

Patients may not drive a car for at least 24 hours after the surgery and must keep the eye area dry and elevated for a week. Patients are also advised to keep their head higher than their heart during that week, and not to bend over. They may carry on with activities such as housework, walking and using an exercise bicycle right away but should avoid strenuous activity and dusty or dirty environments for about a month.

Vision improves gradually

A patient's vision will be blurry right after the procedure, and in general will not be at its best until at least 12 - 18 months after the corneal transplant. Glasses may be prescribed if they help improve vision, and changed as often as needed.

Final vision results will depend on the state of the rest of the eye. If the rest of the eye is healthy, the vision should be excellent. If the retina is scarred or swollen, vision will be only somewhat clearer.

Very successful surgery

As with any operation, corneal transplant surgery carries some risk. Problems such as infection or bleeding can occur, but these are very rare. The chance of a serious complication is about one per cent. This means an individual could have less vision or even no vision in the operated eye after surgery if a complication that cannot be treated arises. The vision in the other eye will remain as it was before the surgery. Fortunately most eye surgery is uneventful, and the chance of improving the vision and/or relieving discomfort is excellent.

Rejection rare

Unlike with a kidney or heart transplant, systemic anti-rejection medication is usually not needed after a corneal transplant. The usual medication needed is eye drops only, and these are continued in decreasing doses for about nine months.

On rare occasions, a person's body may reject the new cornea, and turn the transplant cloudy. If this happens, and the symptoms are reported promptly, the rejection can often be reversed with the intensive use of eye drops. In the rare case where the reaction cannot be reversed with medication, another transplant is often successful.

Sometimes the donated tissue does not survive being moved to the eye. This is not a rejection, but a failure of the transplanted tissue. If this rare event should occur, a new transplant can be scheduled.

How do I know if I need a transplant?

When your vision is keeping you from doing things you must do or enjoy doing - such as driving, working, or reading; or you are having pain caused by the cornea, which is not controlled by medication or a contact lens - discuss surgery with your eye care professional. If surgery will not cause a problem for you so far as your general health is concerned, a corneal transplant may be an option for you.

To learn more about the Eye Bank of Canada, visit their website at eyebankofcanada.kensingtonhealth.org/ near you.

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