What is the cornea and what does it do ?
The cornea is the clear outer layer at the front of the eyeball. It acts as a window to the eye. 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 light rays on to the retina (the light-sensitive film at the back of the eye). This “picture” is then transmitted to the brain.
When the cornea is damaged, it can become less transparent or its shape can change. This can prevent light reaching the retina and causes the picture transmitted to the brain to be distorted or unclear.
How is a transplant carried out ?
The type of cornea transplant you have will depend on which part of the cornea is damaged or how much of the cornea needs replacing. The options include:
- penetrating keratoplasty (PK) – a full-thickness transplant
- deep anterior lamellar keratoplasty (DALK) – replacing or reshaping the outer and middle (front) layers of the cornea
A cornea transplant can be carried out under general anaesthetic (where you are unconscious) or local anaesthetic (where the area is numbed and you’re awake). The procedure usually takes less than an hour and, depending on your circumstances, you either leave hospital the same day or stay overnight.
If the procedure involves the transplantation of the outer cornea, the new outer cornea is held in place with stitches, which usually stay in for more than 12 months.
Are there any risks ?
As with all types of surgery, there is a risk of complications resulting from a cornea transplant. These can include the new cornea being rejected by the body, infection and further vision problems.
Around 95% of full-thickness (penetrating) cornea transplants in low-risk conditions, such as keratoconus, last at least 10 years.
After a cornea transplant
The recovery time for a cornea transplant depends on the type of transplant you have. It takes about 18 months to enjoy the final results of a full-thickness transplant, although it’s usually possible to provide glasses or a contact lens much earlier.
Recovery is usually faster after replacing just the outer and middle layers (DALK).
It’s important to take good care of your eye to improve your chances of a good recovery. This means not rubbing your eye and avoiding activities such as contact sports and swimming until you’re told it’s safe.
The type of cornea transplant you’ll be offered will depend on the parts of the cornea that need to be replaced.
Most cornea transplant operations involve transplanting the full thickness of the cornea. However, recent advances in technology mean it’s sometimes possible to only transplant part of the cornea.
A full-thickness transplant is called a penetrating keratoplasty (PK). During this procedure, a circular piece of damaged cornea from the centre of your eye is removed and replaced with the donated cornea. In most cases, a circular cutting instrument (similar to a cookie cutter) called a trephine is used to remove the damaged cornea.
The new cornea is held in place by tiny stitches, which sometimes form a star-like pattern around the edges. You may be able to see the stitches faintly after the operation.
The operation may be done under local anaesthetic or general anaesthetic, and usually takes about 45 minutes. If local anaesthetic is used, you won’t be able to see through the eye during the operation as the anaesthetic temporarily stops the eye working.
Most people have to stay in hospital for one night after a full-thickness cornea transplant.
Recently, techniques have been developed that allow only parts of the cornea to be transplanted. These techniques aren’t suitable for everyone in need of a cornea transplant and they can take longer to perform, but they often have a faster recovery time and a lower risk of complications.
There are several different techniques your surgeon may use, depending on which layers of the cornea are transplanted. Generally, these techniques can be broken down into transplants involving the front portion of the cornea and those involving the back portion.
Most of these procedures are carried out using femtolaser. These procedures can be carried out using either local or general anaesthetic, and you may be able to go home on the same day of the procedure.
Risks of a cornea transplant
As with all types of surgery, there are several risks and possible complications involved with having a cornea transplant.
Some problems are obvious soon after surgery and need emergency treatment. Others may be spotted during follow-up appointments.
Rejection happens when your immune system recognises the donated cornea as not belonging to you and attacks it. It’s quite a common problem, with symptoms of rejection occurring in about one in five full-thickness corneal transplants, although only about 5% of low-risk grafts actually fail because of this. Serious rejection is rare after deep anterior lamellar keratoplasty (DALK).
Rejection can occur a few weeks after a cornea transplant, but it’s more common after several months. The problem can often be treated effectively with steroid eye drops if treatment begins as soon as you notice symptoms.
You should seek emergency specialist advice if you notice the symptoms listed below after having a cornea transplant:
- red eye
- sensitivity to light (photophobia)
- vision problems – particularly foggy or clouded vision
- eye pain
As well as rejection, there is a risk of further problems after cornea transplant surgery. These can include:
- astigmatism – where the cornea is not a perfectly curved shape
- glaucoma – where pressure builds up in the eye as a result of trapped fluid
- uveitis – inflammation of the middle layer of the eye
- retinal detachment – where the thin lining at the back of your eye called the retina begins to pull away from the blood vessels that supply it with oxygen and nutrients
- the original eye disease (such as keratoconus) returning
- wounds from surgery reopening
- internal infection as a result of surgery wounds
Looking after your eye
- don’t rub your eyes
- during the first weeks after surgery, avoid strenuous exercise and heavy lifting
- if you have a job that does not involve physical strain, you can return to work two to three weeks after surgery
- if your job involves manual labour, you should wait for three to four months
- avoid smoky or dusty places as this could irritate your eyes
- if your eye is sensitive to light, wearing sunglasses can help
- avoid contact sports and swimming until you’re given clear advice that it’s safe, and wear protective goggles when resuming contact sports
- bath and shower as normal, but be careful not to get water in your eye for at least a month
- don’t drive until your specialist tells you it’s possible
You’ll usually be given a patch to wear at night for the first few weeks after surgery to help protect your eye.
For all types of cornea transplant, you have to use steroid or antibiotic eye drops daily. These are normally required for several months, although some people may need to use them for more than a year. The drops reduce swelling and inflammation and help prevent infection and rejection.
At first you’ll need to attend regular follow-up appointments. These should gradually become less frequent over time.
If stitches were used to hold the transplant in place, these are initially left in place to allow the cornea to heal. They are usually removed after about a year.
The time it takes for your vision to return after a cornea transplant can range from as little as a few weeks up to a year or more. This largely depends on the specific procedure used. In some cases, your vision may fluctuate between being better or worse before it settles down.
It’s likely you’ll need corrective lenses (either glasses or contact lenses), even after your vision returns.