What is the cornea?
The cornea is the transparent dome at the front of the eye through which the iris (the coloured part of the eye) and the pupil (the black hole in the centre of the eye) can be seen. The cornea is responsible for most of the focusing power of the eye. It has to be clear, smooth and regular for individuals to see clearly. If the cornea is deformed, damaged or hazy/scarred sight will be impaired.
Why do people have corneal grafts?
The usual reason for performing a corneal graft (transplant) is to enable patients to see more clearly. Occasionally the operation may be advised to help reduce chronic eye pain or to save the eye if there is an ulcer or trauma which has perforated (ruptured) or is threatening to perforate the cornea.
What is a corneal graft and where does the new cornea come from?
A corneal transplant or graft is an operation in which part, or all, the cornea is removed and replaced with healthy corneal tissue from an individual who has died and donated their cornea for transplantation. Permission has always been obtained from the deceased prior to death or from his/her family. Without the generosity of these corneal donors it would be impossible to perform corneal transplant operations and give the gift of sight to hundreds of people each year.
Prior to transplanting the donor’s cornea, it will have undergone a number of tests to make sure it is suitable and healthy. The cornea is normally stored in an Eye Bank for a short period before being sent to the hospital where the operation is performed. As well as ensuring the health of the cornea to be transplanted is good, a number of checks and blood tests are also performed to ensure that the recipient patient will not catch any form of infection (such as HIV/AIDS and Hepatitis C) from the new cornea.
The corneal graft operation
A corneal transplant is normally performed under a general anaesthetic. Blood and other tests are sometimes performed to ensure patients are in good health for the general anaesthetic. A corneal transplant usually takes between 30 to 60 minutes. It involves the eye surgeon removing a circular portion from the centre of the cornea and replacing it with a similar sized circular area from the donor’s cornea, which is then stitched into place with very fine stitches (also called sutures). The surgery is performed with the help of a microscope. In some cases other procedures such as cataract removal and glaucoma operations may be done in combination with corneal transplant. The diseased part of the cornea that has been removed is occasionally sent to laboratory for examination under a microscope
Following the corneal transplant, some soreness in the eye may be experienced and usually the eye is padded with a plastic protective shield taped over it. This is removed 12-18 hours following the surgery.
Complications which may occur weeks/months/years after surgery
There is a danger of rejection of corneal transplant because the patient’s normal immune defence mechanisms may recognise the donor cornea as foreign and try to attack it. The quicker a rejection episode is diagnosed and treated the better is the chance of recovery. It is therefore important that patients are aware of the signs that the corneal graft might be undergoing rejection and, therefore, if one or more of the following symptoms are experienced patients need to contact their eye surgeon immediately:
- a decrease in sight
- redness of the eye
About one in seven patients who undergo a corneal graft will have an episode of rejection. Some patients are more at risk than others such as those who have blood vessels that have grown into the cornea from previous infections and inflammations, those who have had previous grafts and those with other eye diseases such as glaucoma. Most rejection episodes occur in the first year after surgery. However, it can occur at any time, even years later. If rejection occurs, it is treated with steroid eye-drops and occasionally steroid tablets or injections. These may need to be continued for many months and occasionally permanent steroid eye drops are required.
2. Water-logging of the cornea due to failure of the endothelium
In order to maintain transparency the normal cornea is maintained in a dehydrated state by a single layer of cells on the innermost surface of the cornea called the corneal endothelium. In the human, endothelial cells do not re-grow i.e what you are born with is what you get. These cells can fail with time especially if the reason for corneal grafting was due to failure of these cells in the first place, if the donated cornea had relatively few cells in the first place or the surgery was complicated causing loss of endothelial cells. Symptoms of endothelial cell failure include blurred vision especially in the morning on waking, the appearance of coloured halos seen around lights and eye irritation. These eyes often require repeat corneal grafts.
3. Recurrence of the original disease
This can occur if the graft was done because of a genetic disease such as a corneal dystrophy or keratoconus or infection such as herpes virus.
Eye surgery and the long-term use of steroid eye drops are associated with the development of cataract (a clouding of the lens within the eye). This may require further cataract surgery if it becomes symptomatic.
5. Astigmatism (asymmetrical curvature/distortion of the cornea)
Some degree of astigmatism, where the corneal has an asymmetrical curvature, is very likely after corneal grafting. This can be corrected with glasses, but occasionally requires contact lenses if the astigmatism is of a high degree of if there is associated long or short-sight. If astigmatism is present some surgeons may adjust or remove some of the stitches during the first months after surgery. In a few cases a corneal graft can result very severe astigmatism and if contact lenses are unable to correct this or cannot be worn a further operation to improve the shape and focusing of the cornea may be required. These procedures include peripheral cuts (astigmatic keratotomies), re-suturing and Excimer laser eye surgery and may be necessary in about 30% of cases.
If you are researching corneal transplant, laser eye surgery or searching for an Ophthalmologist Cape Town, please contact one of our practices where our qualified assistants are able to provide professional and friendly guidance.
Enquire About Corneal Grafts
If you would like to make an appointment please complete the form below and we will get back to you shortly.