Corneal Grafts

Corneal Grafts

A corneal graft is a transplant operation, involving removal of the central part of the cornea (the clear front window of the eye) and its replacement with a cornea from a donor.
A corneal graft may be performed in isolation or together with another procedure, such as cataract surgery. It takes a long time to recover from a corneal graft operation we hope this information sheet will help you to understand what to expect. However, it is not possible to provide specific, tailored information in this way. Your surgeon will give you additional information based upon knowledge of your own case.
Most of the information in this document concerns a full thickness (penetrating) corneal graft. There is a section at the end giving information about partial thickness (lamellar) grafts.

The Normal Cornea

The Cornea is like a lens, and it must serve 2 functions:

  • Remain clear
  • Focus light on the retina by having the correct amount of curvature.

If the cornea is not clear it will block light coming into the eye. This may result from: scarring by infection or inflammation; swelling with fluid from inside the eye; inherited disorders; trauma; metabolic disorders, and other reasons. The vision may be compared to looking through a murky window.

If the curve of the cornea is not right, then light will be focused in front of the retina (short sighted), behind the retina (long sighted), or in multiple places (astigmatism). This results in blurred vision.

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Inner Layer Corneal Transplant
Full Thickness Corneal Transplant

Why Do You Need This Operation?

Most corneal grafts are performed to clear the path of light into the eye when the cornea is not transparent. Other corneal grafts may be performed to help in the treatment of chronic pain and irritation in the eye. In that case, the operation may be worthwhile even if it does not greatly improve your vision. Rarely, the operation may be advised in order to save the eye, for example if there is very severe corneal ulceration. It is very important that you understand why a corneal graft is being considered, and that you and your surgeon agree what it is hoped the operation will achieve.

The Operation Itself

Most corneal grafts are performed to clear the path of light into the eye when the cornea is not transparent. Other corneal grafts may be performed to help in the treatment of chronic pain and irritation in the eye. In that case, the operation may be worthwhile even if it does not greatly improve your vision. Rarely, the operation may be advised in order to save the eye, for example if there is very severe corneal ulceration. It is very important that you understand why a corneal graft is being considered, and that you and your surgeon agree what it is hoped the operation will achieve.

Where Does The New Cornea Come From?

Your cornea will have come from someone who has expressed a wish that their corneas be used to help someone else to see, after their death. The donor’s cornea will have been thoroughly tested and kept in an Eye Bank for a period, before being sent to the hospital where the operation is to be carried out. The Eye Bank ensures that your new cornea is in good condition and that you will not catch any form of infection from the new cornea. You should note that, once you have had a corneal graft, you would not be able to be a blood or organ donor.

The Operation Itself

This is usually done under a full (general) anaesthetic although if your general health is poor it may be possible to use local anaesthetic. It takes between one and two hours. During the operation the surgeon removes a circular piece of your cornea and replaces it with a similarly sized piece of the donor’s cornea, which is stitched into place. In some cases other procedures, such as cataract extraction, may be done in combination with the corneal graft. These may increase the duration of the operation. You will awaken with some soreness in the eye and find that a protective shield has been taped over it. You will be allowed up and about after the operation. You may be allowed home the same day or, if not, one or two days later. The part of your own cornea that is removed will either be examined under a microscope for further information, kept for research, or discarded in an appropriate and respectful manner.

After The Operation

You should expect some discomfort and irritation of the eye, but pain after a corneal graft is seldom severe. The discomfort usually settles within a few days.

Treatment And Supervision

It is important to use steroid eye drops after the operation to ensure that your eye doesn’t get too inflamed, which would cause you pain and might damage the graft. They are also the most important protection against rejection. Steroid drops can have side effects, which must be watched for. They can cause pressure rises inside the eye, they reduce resistance to infection and, with very prolonged use, can cause cataracts. Therefore, you will be examined regularly to monitor the treatment, and you should report promptly to your doctor if you think you have a problem. The steroid drops are slowly reduced in strength and frequency and are not usually stopped until many months after the operation. Some people may need to use them for longer than others. Most patients can expect to attend the clinic between eight and ten times over the first year after a graft, with gradually increasing gaps between appointments. Patients are generally kept under review for several years after the operation.

Seeing Clearly After The Operation

The improvement in vision is rather slow. This is because the cornea takes a long time to heal, and as it does so, shape changes in the cornea lead to changes in the way it focuses light. It is unlikely that your vision will be “stable”, i.e. worth prescribing new glasses or contact lenses, for at least six or twelve months after the operation, and in some people it can longer. When the cornea has settled into its new shape, you will be left with a refractive error, or glasses prescription. In fact, all corneal graft patients have some degree of distortion of their cornea (astigmatism) that needs to be corrected for them to see clearly. A small proportion of corneal graft patients need to have a second (smaller) operation of some kind on their corneas, to reduce the refractive error before glasses or contact lenses can be prescribed. There are three main types of this “secondary refractive surgery”: keratotomies (“relaxing incisions”), resuturing (i.e. replacing sutures or putting extra ones) and laser eye surgery (LASIK or LASEK). A full discussion of them is outside the scope of this document.

Stitches

The very tiny stitches (properly called sutures) that are put into the cornea hold the graft in place but also affect its shape and therefore the way the eye focuses. They are not dissolving sutures and will eventually need to be removed. Two main patterns of suturing are used – interrupted (or individual) suturing (figure 1) and continuous suturing (figure 2). Some surgeons use both methods combined. In some patients it becomes apparent after the operation that the sutures are causing sufficient distortion of the cornea (astigmatism), affecting the quality of vision. It may then be necessary to adjust or remove sutures to reduce the astigmatism.
Adjustment of continuous sutures may be very helpful for some patients. Adjustment may be done in the clinic or in the operating theatre, depending upon circumstances. It enables the cornea to sit more snugly in place, allowing it to focus better.
The exact timing of suture removal varies greatly between patients and has to be decided on an individual basis. Removal of sutures too early after the operation could result in the graft coming apart and requiring re-suturing. Eventually, however, approximately 12 to 24 months after the operation, all your remaining sutures may be removed.

Grafts, Work and Activity

After a corneal graft, your eye is very vulnerable to blows and to the effects of severe straining (bending down, pushing or lifting). You should not take any more exercise than a brisk walk for the first month after the operation. You should avoid lifting heavy objects, and if you have to bend down, do so slowly from the knees, keeping your head up. Get help with hair washing, and do it with your head back, avoiding soap and shampoo in the eye. You should wear an eye shield at night until you are used to not sleeping on the side of the operated eye. It’s a good idea to wear glasses or sunglasses simply for protection, even if they don’t help the vision.

Above all, don’t poke or rub the eye!

If you do an office job, you can usually go back to work after about two weeks. But if your job is more strenuous, you will be advised to stay off work for at least a month, or in some cases even longer. If you drive, you can usually start again after your first check-up, provided that the vision in the other eye remains satisfactory. If you play sports, it is essential to wear eye protection at all times after a corneal graft. Eye protectors for racket sports are available in sports shops. If you swim you should wear goggles (primarily for protection from injury, not contact with water) and you should not dive in. If you play football there is a small risk of serious injury, particularly when heading the ball. Again you should consider eye protectors. You are strongly advised not to play major contact sports such as rugby, judo etc., at any time after a corneal graft, and not to recommence sports until you have been told that it is safe to do so. In the long term, a corneal graft is strong enough to stand the rigours of ordinary life, but an eye with a corneal graft is never as strong as a normal eye and may be split open by a severe blow such as a punch in the eye. Such an injury can cause blindness.

Complications Of The Operation

There are risks attached to any operation, involving the operation itself and the anaesthetic given in order to carry it out. These are some of the most important risks of corneal grafts.

Minor Complications
These may happen from time to time but do not usually affect the result. They include brief periods of raised pressure or leaks of fluid between the stitches from within the eye. These generally settle within a few days of the operation. However, occasionally it is necessary to replace a stitch, or put in an extra one, if a leak doesn’t seal up on its own.

Major Complications
These are rare, but when they occur they can threaten sight or even possibly cause the loss of the eye. They include bleeding within the eye and infection entering the eye. They may require further operations if they occur.

Disease Transmission
Is a possible complication of any transplant – in other words, the recipient could possibly catch a disease from the donor. All corneal donors are tested for the viruses that cause hepatitis and AIDS. However, there is no test that will detect the germ that causes Creutzfeld-Jakob disease (CJD), and unknown viruses may also exist for which there is currently no test. The risk of catching such a disease is unknown, but likely to be small.

Rejection
Is a major complication that can affect any transplant. It happens when your body detects that a piece of tissue from another person, and your immune system then tries to destroy it. About one in seven patients who have a corneal graft will have a rejection attack at some stage, although some patients are at a much greater risk than others. Rejection can start as soon as two weeks after a graft, but is commonest several months afterwards, and may occur years later. The quicker rejection is diagnosed, the better the chance of recovery. If your eye gets red, watery or gritty, and you lose some vision, then rejection may be the cause and you are advised to attend your eye casualty department immediately. If rejection is found, it is treated with very frequent, strong steroid drops, and occasionally with steroid tablets or drip feeds. Most corneal grafts do recover from their rejection attack, but a lot of patients will need to go on with the steroid drops for a long time afterwards, sometimes permanently. Patients who have a high risk of rejection may be given steroid tablets before and after surgery to try to reduce this risk.

Causes Of Failure Of Corneal Implants

A failed corneal transplant is looks cloudy, making the vision very blurred. This list gives the commonest reasons that a corneal transplant may eventually fail. Most patients with a failed transplant can be offered another one, but individual circumstances will dictate what is recommended in each case. Rejection (discussed above) may lead to failure of the transplant, which may happen immediately or sometimes may happen some time later. Failure of the endothelium (or decompensation) means that the graft no longer has enough cells on its inner surface to keep it clear, and so it must be replaced. Recurrence of the original disease can happen to people whose corneal graft was done because of a genetic disease (corneal dystrophy) or an infection (viral keratitis). Infection causing ulceration leading to scarring may occasionally cause graft failure.

Lamellar Grafts And How They Differ

The word “lamella” means layer, and a lamellar graft describes replacement of part, rather than all, of the thickness of the cornea.

normal cornea

For the purpose of surgery, we think of the cornea as being made up of 2 parts:

  • The front = epithelium, Bowman’s and stroma;
  • The back = Descemet’s and endothelium

If the cornea only has a problem in one part (e.g. a scar in the stroma), it may be possible to replace only that part of the cornea. This leaves normal, healthy tissue in place. While the general experience of a patient undergoing a lamellar graft will be similar to that of a patient having a penetrating graft, there are some slight differences.

Advantages Of A Lamellar Graft

Front part replaced, back part left alone

The most common and most serious type of rejection occurs against the deepest layer of the cornea (the endothelium). If this is not replaced then rejection is much less likely to occur. This in turn means that less steroid drops are needed. Also, the eye retains some structural strength and may be a little less vulnerable to injury. Finally, it is possible that stitch removal may safely be done a little sooner after the operation.

Back part replaced, front part left in place

If only the endothelium is not working properly, it may be possible to replace it through an opening at the side of the cornea. This means that sutures are less likely to be needed, there will be less astigmatism and refractive error, and the visual recovery will be faster Please note however that only a minority of patients needing corneal grafts are suitable for a lamellar operation. For the rest, a lamellar graft would be of no benefit.

As with any surgical procedure, there are risks of which you must be aware. Your doctor will explain these risks to you and ensure that you understand them completely. You will be given time to discuss all issues to your satisfaction.

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