Penetrating Keratoplasty (PK) is a form of corneal transplant surgery in which the full thickness of the central cornea is replaced.
When is PK performed?
PK surgery is performed when the cornea has become scarred or damaged, either through disease or injury, or is leaking due to a very severe corneal ulcer.
What are the benefits of PK?
The first PK was performed over 120 years ago, so it is a well-understood operation. Because the damaged tissue is replaced with a clear graft there is usually a good improvement in vision. However, because the graft is stitched into the eye, there is usually some astigmatism and most patients need contact lenses or glasses to achieve the best possible vision.
What does the surgery involve?
PK is usually performed under general anaesthetic to reduce the risk of surgical complications, unless a patient has health problems that might make a general anaesthetic unsafe. During surgery the cornea is measured, a circular trephine is used to cut out a 7-8mm disc of damaged tissue, a matching disc is prepared from the donor cornea, and stitched in place with microscopic sutures.
What happens after surgery?
The pad can be removed the morning after surgery, and the skin around the eye gently bathed with cooled, boiled, water. The pad may be blood-stained or sticky – this is normal. It’s best not to swim for two weeks after surgery, and to keep the eye as dry as possible when showering or washing hair. The eye will be scratchy and sore for the first few days, but should slowly settle. Normal painkillers can be taken.
What are the potential complications?
As with all surgery, there is a risk of infection. Specific to PK surgery is the risk of expulsive haemorrhage, which can occur when the eye is ‘open’, before the new one is safely stitched in place. This very serious complication is fortunately very rare (around 1 in 200 cases), and is associated with raised blood pressure, fragile blood vessels, or coughing and straining during local anaesthetic surgery.
After the operation the eye is less strong, and direct blows to the eye may break the stitches and damage the graft. For this reason it is recommended to wear the clear plastic shield at night for the first couple of weeks after surgery.
What drops do I need afterwards?
A combination of steroid (Dexamethasone) and antibiotic (Chloramphenicol) drops are needed to prevent infection, promote healing, and reduce the risk of graft rejection:
- Dexamethasone 0.1% preservative-free
– 2-hourly for one week
– 6 times a day for one week
– 4 times a day for one month
– and then slowly tapered off over a year
- Chloramphenicol 0.5% preservative-free four times a day for one month.
As with all transplant operations there is a risk of the body rejecting the donor tissue. This can usually be controlled with eye-drops, but if you experience redness, pain, or reduced vision in the operated eye at any time after surgery it is very important to seek ophthalmic attention.