Penetrating Keratoplasty (PKP): The Foundational Approach to Corneal Transplantation

The cornea, the transparent front surface of the eye, is critical for focusing light and achieving clear vision. When its clarity or structural integrity is severely compromised by disease, injury, or previous surgical complications, vision can be drastically affected. In such cases, where the damage extends through multiple layers of the cornea, a full-thickness corneal transplant, known as Penetrating Keratoplasty (PKP), has long been the gold standard and remains a vital procedure.

While newer lamellar (partial-thickness) techniques have emerged for specific conditions, PKP offers a comprehensive solution when the entire corneal thickness is compromised.

Understanding Penetrating Keratoplasty (PKP)

Penetrating Keratoplasty involves the surgical removal of the patient’s entire central diseased or scarred cornea. This is typically done using a specialized circular blade called a trephine. A precisely matched full-thickness donor cornea (the “graft”), obtained from a human donor through an eye bank, is then carefully sutured into place with numerous, very fine stitches.

The goal is to replace the opaque or misshapen host cornea with a clear, healthy donor cornea, thereby restoring a smooth optical surface and allowing light to pass through unhindered to the retina.

When is PKP Indicated?

PKP is a versatile procedure indicated for a wide range of conditions affecting the full thickness of the cornea, including:

• Advanced Keratoconus: Where the cornea has become excessively thinned and cone-shaped, and other treatments are no longer effective.
• Significant Corneal Scarring: Resulting from infections (e.g., herpetic keratitis, bacterial or fungal ulcers), trauma, or chemical burns.
• Certain Corneal Dystrophies: Genetic conditions that affect multiple layers of the cornea and lead to clouding or structural instability.
• Corneal Perforation or Thinning: Where there’s a risk of rupture.
• Failed Previous Corneal Grafts: When a prior transplant (either PKP or lamellar) has not succeeded.
• Bullous Keratopathy: In severe cases where the entire cornea is swollen and opaque, and endothelial keratoplasty alone might not suffice.

The decision to proceed with PKP is made after a thorough evaluation, considering the nature and extent of the corneal pathology and the potential benefits versus risks for the individual patient.

The Surgical Process and Considerations

PKP is typically performed under general or local anesthesia. It is a meticulous procedure requiring precision in both removing the host cornea and suturing the donor tissue.

Key considerations associated with PKP include:

• Visual Recovery: This is generally a gradual process. While some improvement may be noted relatively soon, optimal vision often takes many months, sometimes a year or more, as the graft heals and sutures are managed or removed.
• Astigmatism: Due to the nature of a full-thickness graft and the presence of sutures, significant astigmatism (irregular corneal curvature) is common after PKP. This often requires correction with glasses, specialized contact lenses, or sometimes further refractive surgical procedures.
• Suture Management: The sutures typically remain in place for an extended period, often for a year or longer, and are selectively removed or adjusted by the surgeon to help shape the cornea and manage astigmatism.
• Graft Rejection: The body’s immune system can sometimes recognize the donor cornea as foreign and attempt to reject it. This is a risk with any transplant, and long-term use of topical steroid eye drops is usually necessary to minimize this risk. The risk is generally higher with PKP than with lamellar procedures.
• Structural Integrity: While the graft heals strongly, the eye may be somewhat more susceptible to injury after PKP.

The Enduring Role of PKP

Despite the advancements in lamellar keratoplasty techniques, PKP remains an indispensable tool in the corneal surgeon’s armamentarium. For many patients with severe, full-thickness corneal disease, it offers the best, and sometimes only, chance for significant visual restoration. It is a well-established procedure with a long history of success in treating complex corneal conditions.

While the recovery can be longer and more involved than with some newer techniques, the potential to restore sight for individuals with otherwise intractable corneal blindness makes PKP a cornerstone of ophthalmic surgery.