Corneal Transplant
Corneal transplants, including partial thickness or lamellar keratoplasties, are performed to replace diseased or scarred cornea with healthy donor tissue.
Endothelial keratoplasty
Dr Ang is a specialist in corneal transplants. After ophthalmology training in Western Australia, Dr Ang undertook two prestigious international fellowships in Corneal and Anterior Segment Surgery at the Cincinnati Eye Institute and the Singapore National Eye Centre. She is an active member of the Australian and New Zealand Cornea Society.
Why do I need a corneal transplant?
The cornea is the clear window at the front of the eye, responsible for focusing light through the eye. Many diseases, including infection or trauma or dystrophies, can affect the clarity of the cornea and compromise the vision.
A Corneal Transplant or Corneal Graft can be performed, where the diseased cornea is replaced by a healthy donor cornea.
The most common conditions that may require a corneal transplant include:
Fuchs Endothelial Dystrophy
Keratoconus
Corneal infection
Corneal scarring from trauma/infection
What types of corneal transplants are there?
Full thickness penetrating keratoplasty
A penetrating keratoplasty (PK) involves replacing the full thickness of the diseased cornea with a donor cornea. The diseased cornea is essentially punched out with a round trephine, and the new donor cornea is sutured in place. The wound needs to fully heal before the sutures are removed, usually 12 to 18 months post-operatively.
This mean it can take over 18 months for the post-operative vision to stabilise. Some people also require further surgery or laser treatment to improve the shape of the graft to allow contact lens fitting or spectacle correction.
Partial thickness keratoplasty
This involves only replacing the diseased layer of the cornea. Deep anterior lamellar keratoplasty (DALK) involves replacing the front layers of the cornea, leaving the back endothelial cell layer intact. This technique may be used in patients with keratoconus, where the endothelial cells remain healthy. The advantage of this technique over PK is that there is reduced risk of rejection.
Penetrating keratoplasty
Endothelial keratoplasty (EK) is used to replace only the diseased endothelial cell layer, in conditions such as Fuchs endothelial dystrophy. In this condition the endothelial cell layer does not work properly, and cannot pump fluid out of the cornea to keep it transparent. Endothelial cells do not regenerate if diseased or damaged and must be replaced by a corneal transplant. Endothelial keratoplasty has a number of potential advantages compared to a full-thickness transplant: healing is much faster and there is a lower chance of rejection.
Endothelial keratoplasty
Where does the donor tissue come from?
The donor corneal tissue comes from the Lions Eye Bank in WA, where the tissue is carefully screened with strict selection criteria. Thanks to the kindness of donors and their families, about 250 corneal transplants are performed in WA each year.
What are the risks of corneal transplantation?
There is a risk of rejection of the graft, as it is a transplant of living tissue. This can occur in up to 20% of grafts, but fortunately is usually reversible with treatment. Steroid eye drops are used for at least 2 years post-operatively to reduce the risk of inflammation and rejection.
There are also other potential risks such as glaucoma and infection.
The transplanted cornea does not last forever and the longevity depends on many factors such as the type of corneal transplant, the underlying condition, and the presence of co-morbid eye conditions such as glaucoma. If the graft fails then it can usually be replaced with another graft, but each subsequent graft may not survive as long as the previous one.