Corneal Transplant
After specialist ophthalmology training at Royal Victorian Eye and Ear Hospital, Dr Li completed two prestigious subspecialty fellowships in Cornea and Anterior Segment surgery at the Royal Perth Hospital and the Manchester Royal Eye Hospital.
What is the cornea?
The cornea is the clear window of our eye. It helps focus light and is needed to see. There are three main layers in the cornea:
Outer or epithelial layer. This layer needs to be smooth for good vision. This layer is damaged if you have a scratched cornea or corneal abrasion.
Middle or stromal layer. This layer makes up most of the thickness of your cornea. Damage to the cornea, infection or corneal swelling that lasts a long time can cause scarring in this layer. These problems can later cause cloudy or distorted vision.
Inner or endothelial layer. This layer has thousands of pump cells pushing fluid out of the cornea, helping to keep it clear. Cells in this layer can be damaged by age, injury, inflammation, other eye surgery, or a disorder such as Fuchs’ corneal dystrophy. These and other problems can cause poor vision if the cornea gets swollen and cloudy, which means you may need a corneal transplant to improve vision.
What is a corneal transplant?
A corneal transplant, also known as keratoplasty, is a surgical procedure that involves replacing a damaged or diseased cornea with a healthy donor cornea. During the surgery, Dr Li will remove the central portion of the damaged cornea and replace it with a clear donor cornea. The new cornea then gradually integrates with the surrounding tissue, ultimately restoring clarity and function to the patient's vision. After the procedure, patients require diligent post-operative care and regular follow-ups to monitor the healing process and ensure the success of the transplant.
What are the different types of corneal transplant?
1. Penetrating Keratoplasty (PK) is where the full thickness of the cornea is replaced by donor cornea. PK full-thickness corneal transplant surgery addresses the problems in all layers of the cornea. Rejection rates for PK are fairly low, about 15%. Usually, eye drops are used to treat rejection.
There are some disadvantages of PK. Recovery from PK surgery usually takes longer than other types of corneal transplants. Dr Li performs PK using 16 stitches to hold the new cornea in place and they are usually left in place for 12 months as the graft integrates with your cornea. Rarely, there can be problems with the stitches. For instance, if the stitches break or loosen, you could get an infection or rejection. Trauma may open up the wound. More than other forms of corneal transplant, PK surgery has higher chance of having post-operative astigmatism, although this can be corrected with glasses, contact lenses or further surgery.
2. Deep Anterior Lamellar Keratoplasty (DALK). The outer epithelium and middle stromal layer are replaced in DALK, but your inner endothelial layer is preserved.
The advantages of DALK include lower risks of rejection risks with DALK than PK as the inner endothelial layer is preserved. In addition, given the intact inner layer, this offers a potential advantages in terms of reduced risk of wound dehiscence after trauma compared to full thickness
Disadvantages of DALK is that it can take longer time than PK surgery. DALK is not suitable for patients with full thickness corneal issue or deep scar.
3. Descemet Stripping Automated Endothelial Keratoplasty (DSAEK). Only your inner endothelial layer is removed. This layer is replaced with a thin disc of donor endothelial cells plus a thin layer of corneal stromal tissue. This tissue is kept in place with an air bubble right after surgery. The air bubble is gradually reabsorbed by your body.
Advantages of DSAEK include:
· DSAEK surgery often takes less time than PK surgery.
· The ophthalmologist only needs to make a small opening in your eye.
· The wound tends to heal faster and is less likely to split open from trauma, compared to PK.
· Your vision is likely to improve more quickly than after a PK.
· There is less risk of astigmatism with DSAEK compared with PK.
· The rejection rate is lower (about 10%)
Disadvantages of DSAEK include:
· DSAEK does not address full thickness defect as in PK
· The DSAEK tissue may not stay in place, which may require more air inside your eye to reattach the tissue.
· You will need to lay flat on your back as much as possible for a few days after surgery.
4. DMEK (Descemet’s Membrane Endothelial Keratoplasty). This corneal transplant surgery is even newer than DSAEK. With this technique, Dr Li inserts an even thinner disc of tissue. This layer has only endothelial cells on a thin membrane. There is no stromal tissue.
Advantages of DMEK, compared to DSAEK, include:
· The DMEK surgical opening is often even smaller than with DSAEK.
· Your vision may return somewhat faster than with DSAEK.
· You might see somewhat better after this surgery than with DSAEK.
· There may be less rejection than with DSAEK (<1%)
Disadvantages of DMEK include:
· Because the donor tissue is so thin, there is a greater risk that the tissue will detach from your own cornea with DMEK compared to DSAEK. This could happen within days after surgery. You may need more surgery to reposition the donor tissue.
· As with DSAEK, DMEK does not remove large amounts of corneal scarring.
· You will be asked to lay flat on your back as much as possible for a few more days longer than with DSAEK.
What are the risks with corneal graft surgery?
As with all surgery, there are small risks with PK, DALK, DSAEK, and DMEK corneal transplant surgery. Possible risks can include haemorrhage (bleeding) in the eye, infection, retinal detachment, rejection of the graft or donor tissue or failure of the graft.
Where is the corneal donor tissue from?
In Western Australia corneal tissue is prepared by the Lions Eye Bank. All donor tissues undergo a stringent process to exclude transmissible infection and to ensure best patient outcome.