Keratoplasty

Keratoplasty is a surgical procedure in which the damaged, opaque corneal tissue at the front of the eye is replaced with a healthy, transparent donor cornea from a deceased donor.

Modern advances in penetrating (full-thickness) and lamellar (partial-thickness) keratoplasty have significantly improved surgical outcomes due to technological developments, improved medications, and enhanced tissue preservation techniques. The success of the surgery depends on several factors, including surgical technique, preoperative evaluation, and postoperative care.

LAMELLAR (Partial-Thickness) KERATOPLASTY

Lamellar keratoplasty is performed to treat corneal thinning or improve optical clarity using a partial-thickness donor cornea. It is classified into:

• Anterior lamellar keratoplasty
• Posterior lamellar keratoplasty

Since anterior lamellar keratoplasty does not involve donor endothelium, there is no risk of endothelial rejection. This method is suitable for anterior corneal pathologies, as the posterior cornea remains unaffected.

In posterior lamellar keratoplasty, only the endothelium is replaced, maintaining the anterior corneal structure, which results in a smoother and more precise surface.

Comparison with Penetrating Keratoplasty (PKP)

Advantages:
✔ Eliminates endothelial rejection risk
✔ Lower risk of intraocular infection (endoophthalmitis)
✔ Shorter recovery time compared to full-thickness keratoplasty

Disadvantages:
❌ Technically more challenging
❌ Potential donor-recipient interface haze and abnormal vascularization

Penetrating keratoplasty (PKP) offers better visual outcomes, but carries a higher risk of endothelial rejection and intraocular infections.

PENETRATING (FULL-THICKNESS) KERATOPLASTY (PKP)

Penetrating keratoplasty involves removing and replacing the entire thickness of the diseased cornea with a healthy donor cornea. It is performed to treat corneal thinning, perforation, or severe vision loss.

Indications for PKP:

• Keratoconus
• Bullous keratopathy
• Graft failure
• Fuchs’ endothelial dystrophy
• Corneal scars (opacity)
• Chemical burns
• Corneal ulcers
• Corneal dystrophies and degenerations
• Herpetic keratitis (eye herpes)
• Trauma-induced corneal failure

PKP has high success rates for keratoconus, bullous keratopathy, and Fuchs’ endothelial dystrophy. However, in cases with vascularized corneas due to recurrent infections or previous graft rejection, the success rate decreases.

Preoperative Considerations for PKP:

• Patients with retinal, optic nerve disorders, or amblyopia may not benefit visually.
• Preoperative control of intraocular pressure (IOP) is crucial to reduce excessive bleeding and prevent donor graft failure.
• Conditions affecting the eyelids or tear film, such as blepharitis, trichiasis, and eyelid malformations, can negatively impact surgical outcomes.
• Uveitis (ocular inflammation) must be controlled before surgery, as it increases the risk of graft failure.
• Previous herpetic keratitis, abnormal corneal vascularization, and inflammatory eye diseases lower the success rate.
• Autoimmune conditions (e.g., rheumatoid arthritis) can cause peripheral corneal thinning, complicating the procedure.

IMPORTANT FACTORS IN DONOR SELECTION

Donor corneas are not suitable for transplantation in cases of:

• Neurological diseases (e.g., Reye’s syndrome, rabies, Creutzfeldt-Jakob disease)
• Unknown cause of death
• Previous eye surgeries
• Infections (HIV, hepatitis, syphilis)
• Ocular tumors (e.g., retinoblastoma, anterior segment malignancies)

COMPLICATIONS OF KERATOPLASTY

Intraoperative Complications:

• Excessive bleeding
• Injury to ocular structures
• Improper graft positioning
• Expulsive hemorrhage (severe bleeding from the vascular layer)

Postoperative Complications:

🔹 Wound Leakage:

• Occurs due to broken sutures or weak wound healing.
• Requires resuturing to prevent complications.

🔹 Increased Intraocular Pressure (IOP):

• Caused by inflammation or retained viscoelastic materials used during surgery.
• Must be controlled to ensure graft survival.

🔹 Endophthalmitis (Intraocular Infection):

• May occur due to infected donor tissue or post-surgical contamination.
• Requires immediate antibiotic or antifungal treatment.

🔹 Persistent Epithelial Defect:

• Usually heals within the first week post-surgery.
• Delayed healing may occur in dry eye, blepharitis, diabetes, or rheumatoid arthritis.
• Treatment includes topical medications or eyelid surgery if necessary.

🔹 Primary Graft Failure:

• Occurs when the donor cornea fails to function within the first postoperative day.
• May result from donor endothelial damage during surgery.
• If corneal edema persists for several weeks, a repeat transplant is required.

🔹 Suture-Related Problems:

• Loose or infected sutures can cause vascularization and suture abscesses.
• Must be removed if complications arise.

🔹 Graft Rejection:

• Occurs in 21-25% of cases, making it the most common cause of graft failure.
• Symptoms include:
  • Eye pain
  • Light sensitivity
  • Redness
  • Decreased vision

🔹 Types of Graft Rejection:

1. Epithelial Rejection: Identified by a line where the donor epithelium replaces the recipient’s.
2. Subepithelial Rejection: Small inflammatory spots appear in the graft tissue.
3. Endothelial Rejection: Causes corneal edema, inflammatory cells, and iris inflammation.
   • Khodadoust lines (wavy lines on the graft endothelium) may be seen.

🔹 Treatment of Graft Rejection:

• Frequent corticosteroid eye drops
• Systemic corticosteroids for severe cases

🔹 Corneal Ulcers:

• Caused by suture abscesses or persistent epithelial defects.
• Must be treated immediately to prevent complications.

🔹 Disease Recurrence:

• Corneal dystrophies (e.g., lattice dystrophy) may return in the graft.
• Herpes simplex virus (HSV) infections often recur and must be distinguished from graft rejection for proper treatment.

Conclusion

Keratoplasty has become a highly successful procedure with advances in surgical techniques and donor preservation. Lamellar keratoplasty is a safer option with a shorter recovery time, while penetrating keratoplasty provides better visual outcomes but carries higher risks. Early detection and management of complications are essential for successful graft survival and long-term vision restoration.