Penetrating & Anterior Lamellar Keratoplasty

Indications for Keratoplasty

Corneal transplantation is indicated once a cornea is irreversibly compromised in a way that medical therapy, contact lenses, or lesser surgery can't fix: endothelial failure with chronic corneal edema, advanced ectatic disease such as keratoconus with central scarring, scarring from infection or trauma, or a failed prior graft. Fuchs endothelial corneal dystrophy is currently the leading indication for corneal transplantation in the United States. The dominance of endothelial disease as a surgical indication has pushed the field away from full-thickness grafting and toward the layer-specific techniques below.

The central question in choosing a technique is which layer of the cornea is actually diseased. A cornea with healthy endothelium but diseased stroma, as in advanced keratoconus or stromal scarring, is a candidate for a lamellar procedure that leaves the endothelium alone. The reverse case, healthy stroma with failed endothelium, calls for an endothelial-only graft, covered separately on the Endothelial Keratoplasty & Graft Complications page. Full-thickness penetrating keratoplasty remains the right choice only when the whole cornea is compromised, or when a lamellar dissection plane can't be safely achieved.

Penetrating Keratoplasty

Penetrating keratoplasty (PK) replaces the full thickness of the cornea: every layer from epithelium through endothelium is removed by trephination and replaced with a matching donor button. Every lamellar technique, by contrast, replaces only some of the cornea's layers and leaves the rest of the patient's own tissue in place.

The donor button is cut slightly larger than the host trephination, typically 0.25 to 0.50 mm oversized. This compensates for tissue compression during trephination and helps limit postoperative myopic shift, without sacrificing apposition between donor and host wound edges.

Suturing and Postoperative Astigmatism

Suture technique has a direct, lasting effect on postoperative astigmatism. A running suture distributes tension evenly around the wound, and its tension can be redistributed after surgery to correct astigmatism as the eye heals. Interrupted sutures can't be adjusted this way once placed, which is the running suture's real advantage for astigmatism control.

Deep Anterior Lamellar Keratoplasty (DALK)

DALK removes diseased stroma down to the level of Descemet membrane, leaving the patient's own healthy Descemet membrane and endothelium in place. Endothelial rejection is the most serious form of graft rejection, and because DALK transplants no donor endothelium at all, that risk disappears entirely. That is DALK's central advantage over penetrating keratoplasty whenever the patient's own endothelium is healthy enough to preserve. Keratoconus, DALK's classic indication, is covered in depth on the Keratoconus & Ectatic Disease page.

The Big-Bubble Technique

DALK's defining technical challenge is separating diseased stroma from the paper-thin Descemet membrane without tearing it. Anwar's big-bubble technique solves this by injecting air deep into the stroma, creating a bubble that pneumatically separates stroma from Descemet membrane along a clean cleavage plane. A successful big bubble allows near-total removal of the diseased stroma in one piece, leaving a smooth Descemet surface behind. The result is a better optical interface and less postoperative haze than manual lamellar dissection without a bubble.

Intraoperative Complications

The technique's central risk is macroperforation of Descemet membrane during the big-bubble dissection. A macroperforation usually rules out safely continuing the lamellar dissection, and the standard salvage maneuver is intraoperative conversion to full-thickness penetrating keratoplasty rather than an attempt to patch and press on.

Boston Keratoprosthesis

Not every eye is a good candidate for a conventional graft, penetrating or lamellar. The Boston keratoprosthesis, an artificial corneal device, is reserved for eyes at high risk of failing a standard transplant: multiple prior graft failures or rejections, or severe ocular surface disease that would compromise a conventional graft's survival. It has no role as a first-line option for a straightforward case like isolated keratoconus or uncomplicated Fuchs dystrophy with a healthy surface; those stay firmly in DALK, PK, or endothelial-keratoplasty territory. The keratoprosthesis is for eyes that have already exhausted conventional options, or would be expected to fail them.

Donor Tissue

Donor corneal tissue must meet specific eligibility and preservation standards before it's suitable for transplantation. Eye banks generally require a minimum donor endothelial cell density around 2,000 cells/mm²: it's the endothelium's pump function that keeps a transplanted cornea clear long-term, so tissue below that density isn't reliable enough to use. Accepted corneas are then preserved in a hypothermic storage medium, typically Optisol-GS, a formulation containing chondroitin sulfate and dextran that extends the safe storage window while keeping the endothelial layer viable ahead of surgery.

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