DALK: A Conservative Approach to Anterior Corneal Disease

The cornea’s remarkable transparency and precise curvature are essential for clear vision. However, certain conditions, often affecting the outer and middle layers, can lead to opacities, structural instability, or irregular shape, severely impairing sight. When such issues necessitate a transplant, but the vital innermost layer – the endothelium – remains healthy, Deep Anterior Lamellar Keratoplasty (DALK) offers a highly selective and effective solution.

DALK represents a significant advancement from traditional full-thickness corneal transplantation (PKP), allowing for a more targeted approach when only the anterior and stromal layers of the cornea are diseased.

Understanding Deep Anterior Lamellar Keratoplasty (DALK)

DALK is a partial-thickness corneal transplant procedure designed to replace the diseased or scarred anterior layers of the cornea while preserving the patient’s own healthy Descemet’s membrane and endothelial cell layer. The surgical process involves carefully removing the affected corneal stroma, leaving behind a thin, smooth layer of the patient’s posterior cornea (Descemet’s membrane with its endothelium). A corresponding anterior lamellar donor graft, prepared from a donor cornea, is then precisely sutured into place.

The procedure often involves a technique known as the “big bubble,” where air or fluid is injected to meticulously separate the diseased stromal layers from Descemet’s membrane, creating an ideal plane for the transplant.

Key Indications for DALK

DALK is particularly well-suited for conditions where the primary pathology resides in the anterior cornea, and the endothelium is healthy and functional. Common indications include:

• Keratoconus: This progressive condition, characterized by corneal thinning and a cone-like protrusion, is the most frequent indication for DALK. When glasses or contact lenses no longer provide adequate vision, and the endothelium is intact, DALK offers a superior option to PKP.
• Corneal Scarring: From infections (e.g., bacterial, fungal, or viral keratitis), trauma, or prior surgeries, provided the scarring does not extend to or severely compromise the endothelium.
• Certain Corneal Dystrophies: Such as granular, lattice, or macular dystrophies, where the opacities are primarily stromal and the endothelium is preserved.

Advantages of DALK Over Full-Thickness PKP

DALK offers several compelling benefits, stemming primarily from the preservation of the patient’s own endothelium:

• Significantly Reduced Risk of Endothelial Rejection: As the patient’s own endothelial cells are retained, the most common and severe form of graft rejection is largely avoided. This often translates to less intensive long-term anti-rejection medication (steroid eye drops).
• Enhanced Structural Integrity: The patient’s intact Descemet’s membrane provides a strong, natural barrier. This results in a more structurally robust eye post-surgery, with a lower risk of rupture from future trauma compared to a full-thickness graft.
• Long-Term Graft Survival: By eliminating the risk of endothelial cell loss from rejection, DALK grafts have the potential for longer functional survival.
• Better Eye Bank Utilization: The anterior donor tissue can be used for DALK, and the posterior tissue might potentially be used for a DMEK procedure in another patient.

Surgical Considerations and Recovery

While the concept of DALK is elegant, the procedure is technically challenging, particularly the precise separation of the corneal layers. It requires significant surgical skill and experience.

Similar to PKP, the visual recovery after DALK is gradual. While some initial improvement may be noted, optimal vision often takes several months to a year as the graft integrates and sutures are managed or removed. Astigmatism can still be a factor, as sutures are used to secure the graft, but it may be more predictable than in PKP.

DALK has revolutionized the treatment of anterior corneal diseases, especially keratoconus. By offering a more conservative and biologically favorable approach, it allows patients to benefit from corneal transplantation while mitigating some of the significant long-term risks associated with full-thickness grafts. It stands as a testament to the ongoing evolution of corneal surgery, providing tailored solutions for complex visual challenges.