A corneal transplant (or keratoplasty) is an operation used to remove a damaged cornea and replace it with healthy corneal tissue from the eye of a suitable donor. A corneal transplant can improve sight and relieve pain in a damaged or diseased eye.
The procedure is normally recommended when the cornea is too misshapen to be treated with other methods, or when damage to the cornea has been caused by disease, infection or injury.
What is the cornea and what does it do?
The cornea is the clear outer layer at the front of the eyeball and acts as a window to the eye. It’s made up of three delicate layers: the epithelium, stroma and endothelium. The coloured iris and the pupil (the black dot in the centre of the iris) can be seen through the cornea.
The cornea helps to focus and transmit light as it’s passed to the lens and onto the retina at the back of the eye. This ‘picture’ is in turn transmitted to the brain.
When the cornea is damaged it can lose its transparency or its shape can alter. This can prevent light from passing to the retina and causes the picture transmitted to the brain to be distorted or cloudy. When you can no longer see through it, a corneal transplant may be needed.
Why is it done ?
The main reason for having a corneal transplant is to improve your sight, alleviate any pain, or repair a perforation if the cornea has ruptured. There are also a number of medical conditions that can lead to the need for corneal transplantation.
Keratoconus This condition affects about 1 in 500 of the population and causes the cornea to weaken, get thinner and change shape. It’s one of the most common reasons for corneal transplantation and usually starts in the early teens, but can occur earlier in a few patients. Many people have this condition in its mild form and can cope well by using contact lenses or glasses – but in some patients it can progress to the point where corneal transplant is necessary.
Endothelial failure This is another common reason for corneal transplantation and commonly affects more elderly patients. The endothelial cells line the inner surface of the cornea and pump fluid to keep the cornea clear. These cells do not get replaced and if they become diseased or damaged, or if there aren’t enough cells to do the job, the cornea becomes waterlogged and cloudy.
Other reasons include corneal dystrophies (rare, inherited disorders that commonly affect both eyes), corneal scarring (after injury, disease or infection), corneal astigmatism and corneal oedema.
How it works?
Corneal transplantation has changed dramatically in the last five years. Until recently, nearly all corneal transplant operations involved transplanting the full thickness of the cornea in an operation called penetrating keratoplasty.
Although penetrating keratoplasty is still commonly used, there are now alternatives, depending on your condition, age and state of health.
Penetrating Keratoplasty (PK)
This is a ‘full thickness’ transplant, performed under local or general anaesthetic. A central circular piece of the damaged cornea is surgically removed and replaced with clear, healthy donor tissue.
The new cornea is held in place by tiny stitches which form a star-like pattern around the edges. You may be able to faintly see them after the operation. The stitches are removed between one to two years later.
The operation can take between one to two hours. On average, penetrating keratoplasty gives the new cornea a survival rate of 15 years.
Risks of a cornea transplant:
Rejection is the process whereby the patient’s own immune system recognizes the donor cornea as foreign and mounts an immune response against it. Rejection episodes are quite common and 1 in 5 patients corneal transplant patients will have a rejection episode. Most rejection episodes can be treated effectively so that the transplant survives and continues to function.
The key is to start treatment promptly. As soon as symptoms are noticed, patients must seek specialist advice as an emergency case.
Symptoms to watch out for include:
Photo phobia (sensitivity to bright lights).
Irritation or pain
Decreased or blurred vision
Treatment is with steroid eye drops and sometimes steroid tablets or injections.
The surface of the transplant can become infected if the stitches holding the transplant in place loosen or break. If infection is not treated it can result in loss of the transplant and even loss of the eye.
This is raised pressure inside the eye damaging the nerve at the back of the eye. The steroid drops used after corneal tranpslantation can cause glaucoma in some patients.
This occurs in approximately one percent of penetrating keratoplasty patients. It is treatable with further surgery.
After cornea transplant surgery:
After penetrating keratoplasty (PK)
You may have to stay in hospital for one to two days afterwards. The eye will be covered with an eye pad, which stays in place until the morning after surgery. When the pad is taken away, you may find that your sight is blurred. This is normal.
You will be given eye drops to use daily – normally for around six to nine months, but some patients may need to use them for longer. The drops reduce swelling and inflammation and prevent infection and rejection. It’s important not to rub your eye and you will be given a patch to wear at night for the first few weeks after surgery.
The stitches holding the transplant are usually left in place for between one and three years. It takes this long for the cornea to heal and be fixed into place.
The shape of full thickness transplants is often quite irregular. This can cause astigmatism (where the transplanted cornea is rugby-ball shaped rather than football shaped). This limits the quality of vision and so you may need further surgery to improve the shape of the transplant and improve the vision. Most patients still need to wear glasses and many wear contact lenses in order to see well after a full-thickness corneal transplant.
Recovering from cornea transplant surgery
Recovery times depend on which treatment you have had. Penetrating keratoplasty (PK)
Recovery can be slow. It can take up to two years for your eye to settle down and give useful vision. In the first few months, your vision may fluctuate as the eye heals. In addition, in some cases further surgery (such as laser treatment) may be needed in order to obtain clearer vision.
Can I return to contact sports?
There is a lifelong risk of wound rupture after PK. Patients returning to contact sports should wear Edgar Davids’-style protective goggles.