Corneal grafting is also referred to as corneal transplantation. This is an operation in which abnormal host tissue is replaced by healthy donor corneal tissue. The graft may be of partial thickness (lamella) or full thickness (penetrating).
Which patients need corneal transplants?
1. Keratoconus
Contact lenses are the most common treatment modality. When contact lenses fail, corneal transplant is the best and most successful surgical option. Despite intensive investigation, the cause of keratoconus remains unclear, but genetic predisposition plays a role.
2. Accidental injuries
Accidental injuries are trauma and chemical burns leading to central scarring of the cornea.
3. Herpes Keratitis and its resultant scarring
4. Inherited corneal dystophies
5. Corneal degeneration
6. Aphakic bullous keratopathy.
This is a condition where the innermost layer of the cornea decompensates, leading to irreversible swelling of the cornea.
A corneal transplant is not like changing a windscreen. The expectations of the patient need to be tempered at a pre-operative stage. Corneal transplantation is a last resort and should be postponed for as long as possible.
A corneal graft can only be done once a donor cornea becomes available. Patients waiting for a corneal graft go on a local waiting list. This is part of a country wide waiting list. Every cornea that becomes available for transplant through the corneal bank in Cape Town, has been tested for infectious diseases such as hepatitis B and HIV.
Surgery
The actual surgery merely initiates an ongoing phase of treatment.
Once a cornea is made available for transplant, the operation has to be done within 3 to 4 days. This operation is to be done under general anaesthesia. In the first few days after the operation, the eye will be light sensitive and scratchy. As the wound starts healing with time, the eye becomes more comfortable.
Post operative complications?
1. Rejection
Although the cornea is the ideal site for an organ transplant, the post-operative result is still confounded by the fact that you are transplanting human tissue, thus risking rejection. With no blood supply, no blood group matching is required. The systematic medication used to counter rejection with all other organ transplants is not used unless a problem occurs.
95% of graft rejection takes place in the first year and can often be reversed with medication. If a rejection episode cannot be reversed, repeat grafts can be done. The best results are obtained if one waits for a 2 – 3 year period to allow the immune system to “forget” and become less sensitive to the foreign tissue against which it launched its first attack. The opaque corneal graft which has been rejected remains in place during this time.
2. Astigmatism
For perfect sight you need a perfect corneal sphere. This is terribly hard to achieve when (on a microscopic level,) you have to suture the circumference of the graft to the receiving cornea of the eye and still hope for perfect healing.
Astigmatism refers to the condition where the shape of the eye is not perfectly spheric, leading to decreased eyesight. Astigmatism can be corrected in various ways, for instance glasses, contact lenses, excimer laser surgery or wound revision. Visual rehabilitation to treat astigmatism can only be done a few months after surgery, once wound healing has stabilised. One year after surgery, corneal sutures can be removed if this becomes necessary.
Each and every eye will behave differently after surgery. Your ophthalmologist will discuss the relevant treatment and correction of astigmatism with you.