Penetrating Keratoplasty (PK) or Full Thickness Cornea Transplant

The cornea is normally clear and compact, allowing light to pass through undisturbed.  Many problems including infection, inflammation, ectasia and scarring can cause the cornea to become cloudy or opaque.  If the cornea is cloudy, light becomes distorted as it passes through and will not focus clearly on the retina.  This leads to blurry vision.  If layers of the cornea become significantly scarred or cloudy, legal blindness may result.

Modern microsurgical techniques can be used to treat a scarred or cloudy cornea.  Remember that the cornea is composed of five layers.  If several of these layers are damaged, a full thickness cornea transplant, or penetrating keratoplasty (PK), can be performed to replace all layers of the cornea.  This type of surgery is done for problems involving multiple layers of the cornea, usually the stroma and endothelium.  If the corneal damage is limited to the front or back of the cornea, a lamellar or partial thickness cornea transplant may be better.  

What does a full thickness cornea transplant involve?

The technique for a PK involves removing a full thickness circular portion of the cornea.  Ideally, this circular portion would encompass all the damaged areas of the cornea and not be too close to the sclera (white part of the eye).  A donor cornea tissue (graft) of similar size and thickness is then transplanted into the same position where the damaged cornea was re
moved. This donor graft is sutured into position by multiple microscopic stitches. This is depicted in the upper image below, where the dotted circle is the transplanted full thickness corneal tissue and the separate lines represent sutures.  The lower image is a cross-sectional view of the cornea, with two dotted lines delineating the edge of the cornea transplant with two grey circular sutures.  

The procedure takes approximately 1 hour to perform and can be done in a hospital or outpatient surgical centre. A PK has a longer recovery time compared with some other types of cornea transplants.  The sutures are generally removed after 1 year, and it may take this long to achieve your best vision.  A PK also has a slightly higher risk or rejection compared with partial thickness cornea transplants.

Rejection can occur in any type of cornea transplant, and results from the body’s immune system attacking the transplanted corneal tissue.  This can typically be managed using topical or systemic anti-inflammatory eye drops or tablets.

If you have a damaged cornea or have poor vision due to corneal scarring or clouding please contact our Melbourne offices to schedule a consultation.  Dr MacIntyre will perform a comprehensive eye evaluation and discuss the possible treatment options available, including the risks, benefits and alternatives.