– When is a corneal transplant needed?
– What happens during a corneal transplant?
– Types of corneal transplant
– Deep anterior lamellar keratoplasty (DALK)
– Penetrating keratoplasty (PK)
– How well do DALK and PK corneal transplants work?
– Endothelial keratoplasty (EK)
– How well does EK corneal transplant work?
When is a corneal transplant needed?
Usually a transplant is considered if your cornea is damaged or distorted to a point where the vision can no longer be improved with glasses or contact lenses and if any treatment you are having is no longer dealing with any pain or discomfort the corneal problem is causing you.
Your ophthalmologist will discuss with you how a corneal transplant will help and they should help you make the decision on when to have your transplant.
What happens during a corneal transplant?
Surgery for a corneal transplant usually takes around an hour, although depending on the type you are having, it may take up to two hours to complete. Transplant surgery can be done under either under local anaesthetic, where you are awake, or general anaesthetic, where you are unconscious and unaware.
If you have a local anaesthetic you will usually have an injection into the soft tissue around your eye, not into your eye itself. You will also be given eye drops to numb the front of the eye.
The injection stops you feeling pain from your eye, reduces what you can see and stops your eye from moving around. You will need to be able to lie still for the whole operation to be suitable for local anaesthetic.
If you have local anaesthetic you might be offered sedation, medication which makes you feel sleepy and relaxed during the surgery. Sedation can make the surgery less stressful and more comfortable for you. Your doctor would be able to explore whether or not sedation would be right for you.
You eye should not be painful following the surgery, but if there is any discomfort you may be given painkillers like paracetomol. The stitches in your eye may make your eye feel gritty, but these should not be uncomfortable or painful. If they are it would be important to contact the hospital about this.
Following surgery your eye will be patched. You can usually go home the same day, but will have to go back within the first week to have your eye checked by your ophthalmologist. During this time you will have to wear a plastic shield at night to protect your eye while you are asleep.
You will need to use anti-rejection, usually steroid, eye drops for at least six months and in some cases for the rest of your life to prevent your body from rejecting the new donor cornea layers. You might need to take other medicines to suppress your immune system if your ophthalmologist feels that there is a high risk of rejection.
After surgery you’ll been given antibiotic eye drops for one to two weeks to prevent infection. You ophthalmologist will advise you how often you will need to use all these medicines and for how long.
After the first week’s check-up, you would typically be seen again within a month and then every three months for the first year. Depending on the type of transplant you have, after the first year further appointments may not be needed. However, some people who have had a corneal transplant will need life-long check-ups.
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Types of corneal transplant
There are three types of corneal transplant.
- DALK – deep anterior lamellar keratoplasty, which removes and replaces part of the front layers of the cornea
- EK – endothelial keratoplasty, which removes and replaces the innermost layers of the cornea
- PK – penetrating keratoplasty, which removes and replaces all the layers of your cornea.
The type of transplant you will be offered depends how the corneal problem you have is affecting your cornea. Corneal transplants can also be used for corneal injuries.
Deep anterior lamellar keratoplasty (DALK)
DALK removes only the top layers from a very small area in the centre of your cornea, leaving behind the innermost endothelial layer.
Your ophthalmologist then places a specially prepared "button" of donor cornea containing these top layers onto your cornea. The donor button has been cut so that it will fit snugly into the area of your cornea which was removed. This button of donor tissue is held in place by tiny stitches until it heals in place.
DALK usually takes about a year to heal. Some stitches may be removed before this, but usually not before the first six months.
Penetrating keratoplasty (PK)
PK is a "full thickness" transplant. This is where your whole cornea is replaced by a donor cornea which is held in place with stitches. PK is more likely to be offered if you have already had a DALK transplant which has not worked, or if the stroma and endothelial (inner) layers of your cornea are damaged.
How well do DALK and PK corneal transplants work?
Both DALK and PK transplants work well. Eighty to 90 per cent of PK transplants carried out for stromal dystrophies are still functioning well after five years. Newer DALK transplants also seem to have an even lower risk of failure, to last for longer and to have shorter recovery times compared to PK transplants.
Although PK transplants are an effective treatment, 50 per cent are no longer working at 20 years. This means that if you are younger you might be advised to wait longer before having a corneal transplant, as you are more likely to require a number of transplants in your lifetime.
Although it is possible to replace a failed or rejected transplant, known as a re-graft, the risk of rejection and failure goes up each time a transplant is done.
The risks of both PK and DALK are low, but after both types of surgery it can take a long time for vision to recover. You will also still usually need to wear contact lenses after the transplant to get the best possible vision.
Following a transplant you will also need to use steroid eye drops for at least six months, and in some cases indefinitely, to prevent rejection of the new transplanted tissue.
Transplants also carry the risk of cataracts, the clouding of the lens in your eye, and glaucoma, a condition where pressure at the front of your eye damages the optic nerve at the back of your eye. These risks are partly due to the need for steroids following the surgery.
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Endothelial keratoplasty (EK)
EK replaces only the innermost layers of the cornea and is only suitable for dystrophies and conditions that affect the endothelial layer of the cornea. The endothelial layer acts as a pump, removing fluid from your cornea to keep it clear. This means that EK transplants cannot be used to treat stromal dystrophies or conditions where the front layers of the cornea are scarred or damaged.
There are two main types of EK transplants, which are very similar:
- Descemet's stripping endothelial keratoplasty (DSEK), also known as a "DSAEK" where the "A" stands for automated.
In DSEK you receive a new endothelium, Descemet's membrane, which is a layer of the cornea found between the endothelium and the stroma, as well as some of the stroma from a donor cornea.
- Descemet's membrane endothelial keratoplasty (DMEK).
In DMEK you receive only the endothelium and the Descemet's membrane from a donor cornea.
How well does EK corneal transplant work?
EK is keyhole surgery, which is quick to heal. By transplanting a thinner layer of tissue in DMEK, recovery times are faster than for DSAEK, the visual results are better and the rejection risk is lower at only one per cent for DMEK, compared to seven to eight percent for DSAEK and 12 to 13 per cent for a full thickness penetrating keratoplasty (PK) transplant. Your ophthalmologist would be able to explore whether or not a DSAEK or DMEK transplant would be right for you.
Corneal transplants are an effective treatment, but with all transplants there is a risk of rejection. This occurs when your body’s immune system recognises the transplanted tissue as foreign tissue and starts to attack it.
It is usually possible to treat corneal transplant rejection with anti-inflammatory eye drops, usually steroids, which reduce swelling. But repeated problems with rejection can lead to the transplant failing and the need for repeat surgery.
Although rejection is a risk and can affect about one in five of all transplants, the risk of rejection is reduced by using steroid eye drops following surgery. Across all types of corneal transplant, 75 per cent last at least five years and more than 50 per cent last up to ten years. EK transplants may also have lower rejection rates.
A helpful way to remember the symptoms of rejection is "RSVP":
- red eye
- sensitivity to light
- vision loss (blurred vision)
If you develop any of these symptoms it is important to seek medical help immediately. Your hospital will advise you what to do if you experience any of these symptoms.
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Being diagnosed with an eye condition can be very upsetting. You may find that you are worried about the future and how you will manage with a change in your vision. We’re here to support you every step of the way, and to answer any questions you may have – just get in touch with our Sight Loss Advice Service.
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