Penetrating keratoplasty (PKP) is a full-thickness corneal transplantation procedure where a damaged cornea is replaced by a healthy donated corneal tissue. It is the most common transplantation procedure performed with approximately 100,000 procedures performed annually worldwide.
A corneal transplant is done for a variety of conditions. These include corneal dystrophys, corneal scarring from infections and trauma, and keratoconus. Indications for corneal transplantation include the following:
- Optical: To improve visual acuity by replacing the patient’s diseased or injured opaque tissue with clear healthy donor tissue
- Tectonic/reconstructive: To preserve corneal anatomy and integrity in patients with corneal thinning or to reconstruct the anatomy of the eye, e.g. after corneal perforation.
- Therapeutic: To remove inflamed or infected corneal tissue unresponsive to treatment by antibiotics or anti-virals.
Procedure of Corneal Transplantation
The surgery is performed in an outpatient surgical center. Upon your arrival you will be given a brief physical examination by the surgical team and then taken to the operating room. In the OR, you will receive a sedative to help you relax followed by either local or general anesthesia.
With anesthesia induced, Dr. Silk and the OR team first prepare the donor cornea for transplantation. The surgical team then cleans the skin around the eye to be operated on and drapes the face around the eye. An eyelid speculum is placed to keep the lids open, and some lubrication is placed on the eye to prevent drying. A metal ring is then stitched to the sclera, which will provide additional stability for the eye during the surgery.
Dr. Silk carefully inspects the patient’s cornea and determines the size of the tissue to be transplanted. The diseased cornea is removed with a type of surgical blade called a trephine. Once this is completed the donor tissue is cut to the appropriate size and then brought to the surgical field where it is carefully sutured into place.
The metal ring is then removed and antibiotic eye drops are placed in the eye. The eye is then patched, and the patient is taken to a recovery area while the effects of the anesthesia wear off. The patient goes home following this and sees Dr. Silk the following day for the first post-operative appointment.
Prognosis of Corneal Transplantation
When the primary purpose of a cornea transplant is to improve visual acuity, the prognosis is dependent upon whether the rest of the eye is healthy. If it is, then it should be possible to recover normal vision. Full visual recovery can take 6 to 12 months and patients may need to use glasses or a hard contact lens to maximize their vision.
Risks of Corneal Transplantation
Traditional corneal transplant surgery has about a 90% success rate, and the rate of rejection is only about 8%. Rejection episodes can often be controlled with topical steroid drops. Graft failure can occur at any time after the cornea has been transplanted, even years or decades later. The causes can vary, though it is usually due to new injury or illness. Treatment can be either medical or surgical, depending on the individual case.
Occasionally, there are problems with sutures, which can come loose, cause infections, or cause astigmatism. The astigmatism after traditional corneal transplant surgery can be significant enough that eyeglasses alone won’t give adequate vision. These patients may ultimately require contact lenses or additional surgery to reduce or eliminate the astigmatism.
Because the wound is full-thickenss and 360 degrees, the corneal transplant wound is not as strong as normal. It is at risk to rupture or break open from mild or incidental trauma, even several years after the surgery.
There is also a slight risk of infection especially during the post operative recovery period. During this time topical antibiotics are used to minimize this risk.