Keratoplasty: Types, Indications, Procedure, and Postoperative Care

Keratoplasty: A Detailed Guide

Introduction

Keratoplasty, commonly referred to as corneal transplantation, is a surgical procedure where a damaged or diseased cornea is replaced with a donor cornea. The primary goal is to restore vision, improve the cornea's structural integrity, or alleviate pain caused by corneal conditions.

Types of Keratoplasty

Keratoplasty can be broadly classified into two categories based on the layers of the cornea being replaced:

1. Penetrating Keratoplasty (PK)

Definition: Full-thickness corneal transplantation where all layers of the cornea (epithelium, stroma, Descemet’s membrane, and endothelium) are replaced.

• Indications:
  • Advanced keratoconus
  • Full-thickness corneal scars
  • Severe corneal thinning or perforation
  • Infectious keratitis unresponsive to treatment
  • Pseudophakic bullous keratopathy
• Advantages: Treats conditions affecting all layers of the cornea.
• Disadvantages: Higher risk of graft rejection and prolonged visual recovery.

2. Lamellar Keratoplasty

Definition: Partial-thickness corneal transplantation where only specific layers of the cornea are replaced.

Subtypes:

• Anterior Lamellar Keratoplasty (ALK): Replaces the epithelium and stroma while leaving the endothelium intact. Commonly performed for superficial corneal scars or keratoconus.
• Deep Anterior Lamellar Keratoplasty (DALK): Removes the epithelium, stroma, and Descemet’s membrane while preserving the endothelium. Indicated for stromal pathologies like keratoconus without endothelial dysfunction.
• Endothelial Keratoplasty (EK): Targets the endothelium and Descemet’s membrane. Subtypes:
  • Descemet’s Stripping Endothelial Keratoplasty (DSEK): Partial replacement of the Descemet’s membrane and endothelium.
  • Descemet Membrane Endothelial Keratoplasty (DMEK): Transplantation of only the Descemet’s membrane and endothelium. Used for conditions like Fuchs' endothelial dystrophy and pseudophakic bullous keratopathy.

Indications for Keratoplasty

Keratoplasty is indicated in various corneal diseases, including:

• Structural abnormalities: Keratoconus, pellucid marginal degeneration.
• Infections and scars: Herpetic keratitis, bacterial or fungal keratitis leading to corneal scarring.
• Endothelial dysfunction: Fuchs' endothelial dystrophy, pseudophakic bullous keratopathy.
• Trauma: Corneal perforation or chemical burns.
• Congenital conditions: Congenital hereditary endothelial dystrophy.

Preoperative Assessment

• History and Examination: Detailed ocular and medical history, corneal examination using slit-lamp biomicroscopy, assessment of intraocular pressure (IOP), and anterior chamber depth.
• Investigations:
  • Corneal topography: To assess corneal curvature and thickness.
  • Specular microscopy: To evaluate endothelial cell density.
  • Ocular coherence tomography (OCT): For detailed corneal imaging.
  • Systemic workup: Rule out systemic infections or contraindications for surgery.

Surgical Procedure

1. Donor Cornea Preparation: The cornea is harvested from a deceased donor (usually within 12 hours postmortem). The donor tissue is evaluated for endothelial cell density, clarity, and the absence of infections.
2. Recipient Eye Preparation: Topical and systemic antibiotics to reduce infection risk. Marking of the diseased cornea for precise alignment of the graft.
3. Procedure: The damaged cornea is excised using a trephine. The donor cornea is sutured to the recipient's eye using fine sutures (10-0 nylon). Sutures may be interrupted or continuous depending on the surgeon’s preference.
4. Duration: The procedure takes approximately 1–2 hours under local or general anesthesia.

Postoperative Care

• Medications: Topical antibiotics, corticosteroids to prevent graft rejection, and lubricants to maintain corneal hydration.
• Follow-up: Regular follow-ups to monitor graft clarity, suture integrity, and rejection signs. Sutures may need to be removed after several months.
• Patient Education: Avoid rubbing the eyes, use protective eyewear, and report symptoms like redness, pain, or reduced vision immediately.

Complications

• Graft Rejection: Signs include redness, pain, photophobia, and decreased vision. Treatment involves intensive corticosteroid therapy.
• Infections: Bacterial or fungal infections can occur postoperatively.
• Astigmatism: Irregularities in the corneal surface can lead to visual distortion.
• Recurrence of Original Disease: Conditions like herpetic keratitis may recur in the graft.
• Endothelial Failure: Loss of endothelial cells can lead to corneal edema and graft failure.

Prognosis

Success rates depend on the underlying condition, surgical technique, and postoperative care. Graft survival rates are generally high for non-inflammatory conditions like keratoconus, while inflammatory diseases pose a higher risk of rejection.