What is corneal grafting?
When a damaged cornea cannot be improved by other treatment, a corneal graft may be performed. This is to replace the damaged cornea or part of it, with healthy corneal tissue. The new cornea is obtained from donated corneas, which undergo thorough testing before being used for transplantation.
What is the cornea?
The cornea is the clear outer layer at the front of the eye. The coloured iris and the black pupil can be seen through the cornea. The cornea helps to focus and transmit light as it passes to the lens and on to the retina at the back of the eye. (When light reaches the retina it is converted into impulses, which are transmitted via the optic nerve to the visual centre in the brain.)
What are the types of corneal grafts?
- Partial thickness or Lamella grafts are used to treat conditions of the cornea where the damage is mostly restricted to the front surface of the cornea and only the front part of the cornea is replaced.
- Full thickness or penetrating grafts are more commonly used and result in the whole of the cornea being replaced.
Who requires corneal grafting?
Young people are often born with abnormalities of the cornea. In a condition known as keratoconus, the cornea develops an abnormal curvature that makes normal vision impossible. Childhood infections such as measles can also cloud the cornea, often causing permanent blindness throughout the person’s life.
In later years, infection or trauma to the eye are the main causes for the cornea to become cloudy and this can reduce the vision.
In older people, degenerative diseases, often caused by excessive exposure to harsh sunlight can cause the cornea to become dull with a resultant loss in vision. Old people then find it increasingly difficult to function. The dull opacified cornea can, however, be transplanted with a new cornea, thus resorting the vision of the patient, whether he be a young child, an adult or an old person.
What is the source of corneas for transplantation?
Corneas are removed from the eyes of people who have died. The individual, or his family, consent to the medical use of the eyes after death.
Corneas are not taken from donors known to have infectious conditions. All donors are screened for carriers of AIDS or Hepatitis viruses before their corneas are used.
There may be delays in obtaining a cornea. If no suitable cornea is available then the recipient will have to wait until the death of a donor for the operation to be performed.
What is the procedure?
Usually a patient will be called to hospital the day before the operation. Urine and blood checks and, in some cases, an ECG (electrocardiogram) will be taken. The operation will last about one hour. The eye will not be removed during operation. A central piece of cornea is cut and removed. This will be replaced by the clear donor cornea, which will have been treated prior to surgery with an antibiotic solution.
The grafted cornea will be sewn with very fine stitches, which may stay in place for up to two years. The cornea can take at least a year to heal completely. After the surgery, the operated eye will be covered with an eye pad and protective plastic eye shield. This will be removed the day after the operation and normal activities may be resumed as and when the individual feels able to do so. Return home is usually within a few days of the corneal graft.
What happens after the operation?
Immediately after the operation, the eyesight will probably be blurred. The eye may water and be sensitive to light. The patient will not have clear and useful sight immediately, and for the first few months after the graft the healing process can cause sight fluctuations.
Corneas vary in shape and sometimes the shape of the donor cornea is different from the one it replaces. Glasses or contact lenses may be prescribed to correct the difference. These are usually given several months after the operation. This is because the cornea takes time to heal.
Since the cornea is transparent there will be very little change to the appearance of the eye. The colour of the eye, which is determined by the iris, will not be affected but stitches may be barely noticeable until they are removed. Older people may develop a white circle around the edge of the cornea which is harmless and is because of ageing, not the operation.Do’s and Don’ts after the operation:
- Do not rub or touch the eye.
- Avoid smoky and dusty rooms, which can cause irritation.
- Wear sunglasses if the eye is light sensitive
- Do not play contact sports and swimming in particular. Ask the doctor if you are unclear which sports you should avoid.
- You will need at least 2-4 weeks off work, but again this will be discussed with you on an individual basis.
- Avoid driving until the doctor tells you otherwise.
What is the aftercare and possible complications?
Corneal grafting offers a reasonable or good prospect of visual improvement where the front of the eye is damaged by injury or disease. Although the success rate is good for many conditions the outcome will be affected by general health and the condition of your eye.
Serious complications following surgery are uncommon but like all major eye operations, there is an increased risk of haemorrhage (bleeding in the eye) or other damage. Complications may include infection or additional eye problems such as cataract or retinal detachment. For this reason it is essential that all follow-up appointments are kept and that any symptoms are treated as an emergency as soon as they are noticed.
The risks of rejection of the graft is low. However, the following signs may indicate that the person should return to the eye hospital for a check-up.
- Increased pain
- Increased redness
- Increased watering or discharge
- Further reduction in the vision
To help prevent infection and rejection, drops will be prescribed which must be applied exactly as directed by the opthalmologist for a period of six months or more. The patient should avoid rubbing and touching his eyes.