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Penetrating Keratoplasty
Cornea
1. Introduction & Clinical Analogy
Clinical Analogy
- Think of PK as a full-thickness 'engine transplant' - unlike a partial replacement (DSAEK/DMEK replacing only the damaged cylinder), PK removes and replaces the entire corneal engine (all 5 layers). This gives maximum optical restoration but comes at the cost of a prolonged recovery, high astigmatism, and lifelong rejection risk - analogous to a heart transplant requiring perpetual immunosuppression versus a valve replacement (lamellar keratoplasty).
Definition
- Penetrating Keratoplasty (PK) is the surgical replacement of a full-thickness disc of diseased or opacified host corneal tissue with a corresponding full-thickness donor button, secured with interrupted or continuous sutures.
- It remains the gold standard for conditions where all corneal layers are diseased or where lamellar techniques are technically unfeasible.
Historical Landmarks
| Year | Event |
|---|---|
| 1905 | • Eduard Zirm - first successful human penetrating keratoplasty • Olomouc, Czech Republic |
| 1940s | • Paton - eye banking established • Corneal storage advances |
| 1960s–1970s | • Introduction of the operating microscope • Finer nylon sutures (10-0) |
| 1986 | • Collaborative Corneal Transplantation Studies (CCTS) launched |
| 2000s | • Femtosecond laser-assisted trephination introduced |
| 2000s | • Lamellar techniques challenge penetrating keratoplasty dominance • Descemet stripping automated endothelial keratoplasty (DSAEK) • Descemet membrane endothelial keratoplasty (DMEK) |
| 2000s–present | • Deep anterior lamellar keratoplasty (DALK) refinement |
| 2010s–present | • Crosslinked donor tissue |
| 2020s | • Bioengineered corneal tissue |
| Year | Event |
|---|---|
| 1905 | • Eduard Zirm - first successful human penetrating keratoplasty • Olomouc, Czech Republic |
| 1940s | • Paton - eye banking established • Corneal storage advances |
| 1960s–1970s | • Introduction of the operating microscope • Finer nylon sutures (10-0) |
| 1986 | • Collaborative Corneal Transplantation Studies (CCTS) launched |
| 2000s | • Femtosecond laser-assisted trephination introduced |
| 2000s | • Lamellar techniques challenge penetrating keratoplasty dominance • Descemet stripping automated endothelial keratoplasty (DSAEK) • Descemet membrane endothelial keratoplasty (DMEK) |
| 2000s–present | • Deep anterior lamellar keratoplasty (DALK) refinement |
| 2010s–present | • Crosslinked donor tissue |
| 2020s | • Bioengineered corneal tissue |
2. Indications for PK
Penetrating keratoplasty (PK) is indicated when the pathology involves all or most corneal layers, or when lamellar alternatives are unsuitable because of posterior corneal or endothelial involvement. The mnemonic A–F covers broad categories:
| Letter | Category | Key Conditions |
|---|---|---|
| A | Anterior/Full-thickness disease | • Advanced keratoconus • Corneal scars (full thickness) |
| B | Burns & Trauma | • Chemical burns with total stromal opacity • Perforations |
| C | Corneal dystrophies | • Macular, granular, lattice (advanced) • Congenital hereditary stromal dystrophy |
| D | Decompensation (endothelial) | • Bullous keratopathy (pseudophakic bullous keratopathy [PBK], aphakic bullous keratopathy [ABK]) • Descemet stripping automated endothelial keratoplasty (DSAEK) or Descemet membrane endothelial keratoplasty (DMEK) preferred |
| E | Ectasias | • Advanced pellucid marginal degeneration with poor visual acuity may require penetrating keratoplasty (PK). • Failure of nonsurgical management, including contact lenses, may require penetrating keratoplasty (PK). • Advanced keratoconus with persistent or visually significant sequelae of hydrops, such as visually significant corneal scarring, may require penetrating keratoplasty (PK). |
| F | Failed grafts | • Re-grafting for primary failure • Re-grafting for late endothelial failure |
| Letter | Category | Key Conditions |
|---|---|---|
| A | Anterior/Full-thickness disease | • Advanced keratoconus • Corneal scars (full thickness) |
| B | Burns & Trauma | • Chemical burns with total stromal opacity • Perforations |
| C | Corneal dystrophies | • Macular, granular, lattice (advanced) • Congenital hereditary stromal dystrophy |
| D | Decompensation (endothelial) | • Bullous keratopathy (pseudophakic bullous keratopathy [PBK], aphakic bullous keratopathy [ABK]) • Descemet stripping automated endothelial keratoplasty (DSAEK) or Descemet membrane endothelial keratoplasty (DMEK) preferred |
| E | Ectasias | • Advanced pellucid marginal degeneration with poor visual acuity may require penetrating keratoplasty (PK). • Failure of nonsurgical management, including contact lenses, may require penetrating keratoplasty (PK). • Advanced keratoconus with persistent or visually significant sequelae of hydrops, such as visually significant corneal scarring, may require penetrating keratoplasty (PK). |
| F | Failed grafts | • Re-grafting for primary failure • Re-grafting for late endothelial failure |
PK vs Lamellar - When to Choose PK?
| Condition | Preferred Procedure | Reason |
|---|---|---|
| Keratoconus | Deep anterior lamellar keratoplasty (DALK) when keratoplasty is required | • Healthy endothelium • Preserves host endothelium • Avoids endothelial graft rejection |
| Keratoconus + hydrops / failed deep anterior lamellar keratoplasty (DALK) | Penetrating keratoplasty (PK) in selected cases | • Significant Descemet membrane injury • Endothelial compromise • Dense scarring • Other full-thickness disease |
| Fuchs' dystrophy | Descemet membrane endothelial keratoplasty (DMEK); Descemet stripping automated endothelial keratoplasty (DSAEK) when Descemet membrane endothelial keratoplasty (DMEK) is unsuitable | • Isolated endothelial disease |
| Bullous keratopathy + stromal scar | Penetrating keratoplasty (PK) | • Stromal disease coexists |
| Full-thickness scar (post-trauma) | Penetrating keratoplasty (PK) when most or all layers are involved | • Replaces opaque, scarred full-thickness tissue |
| Macular corneal dystrophy | Penetrating keratoplasty (PK) when deep stromal, Descemet membrane or endothelial involvement is present | • Disease may extend beyond the layers removable by deep anterior lamellar keratoplasty (DALK) |
| Lattice (advanced) | Penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK) | • Deep anterior lamellar keratoplasty (DALK) if Descemet membrane and endothelium are spared • Penetrating keratoplasty (PK) for deeper disease or failed deep anterior lamellar keratoplasty (DALK) |
| Corneal perforation (acute) | Patch graft or tectonic penetrating keratoplasty (PK) when indicated | • Emergency tectonic management • Choice depends on defect size, depth, location, cause and tissue loss |
| Granular dystrophy Avellino variant | Deep anterior lamellar keratoplasty (DALK) may be preferred when disease is stromal and Descemet membrane/endothelium are healthy | • Preserves host endothelium • Avoids endothelial graft rejection • Recurrence can occur and is not established to be lower after lamellar surgery |
| Condition | Preferred Procedure | Reason |
|---|---|---|
| Keratoconus | Deep anterior lamellar keratoplasty (DALK) when keratoplasty is required | • Healthy endothelium • Preserves host endothelium • Avoids endothelial graft rejection |
| Keratoconus + hydrops / failed deep anterior lamellar keratoplasty (DALK) | Penetrating keratoplasty (PK) in selected cases | • Significant Descemet membrane injury • Endothelial compromise • Dense scarring • Other full-thickness disease |
| Fuchs' dystrophy | Descemet membrane endothelial keratoplasty (DMEK); Descemet stripping automated endothelial keratoplasty (DSAEK) when Descemet membrane endothelial keratoplasty (DMEK) is unsuitable | • Isolated endothelial disease |
| Bullous keratopathy + stromal scar | Penetrating keratoplasty (PK) | • Stromal disease coexists |
| Full-thickness scar (post-trauma) | Penetrating keratoplasty (PK) when most or all layers are involved | • Replaces opaque, scarred full-thickness tissue |
| Macular corneal dystrophy | Penetrating keratoplasty (PK) when deep stromal, Descemet membrane or endothelial involvement is present | • Disease may extend beyond the layers removable by deep anterior lamellar keratoplasty (DALK) |
| Lattice (advanced) | Penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK) | • Deep anterior lamellar keratoplasty (DALK) if Descemet membrane and endothelium are spared • Penetrating keratoplasty (PK) for deeper disease or failed deep anterior lamellar keratoplasty (DALK) |
| Corneal perforation (acute) | Patch graft or tectonic penetrating keratoplasty (PK) when indicated | • Emergency tectonic management • Choice depends on defect size, depth, location, cause and tissue loss |
| Granular dystrophy Avellino variant | Deep anterior lamellar keratoplasty (DALK) may be preferred when disease is stromal and Descemet membrane/endothelium are healthy | • Preserves host endothelium • Avoids endothelial graft rejection • Recurrence can occur and is not established to be lower after lamellar surgery |
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Keep reading Penetrating Keratoplasty
16 more sections are included with the Clinical plan.
- Preoperative Evaluation
- Surgical Technique - Step-By-Step
- Graft Size Selection - Decision Logic
- Postoperative Management
- Complications of PK
- Corneal Graft Rejection - In Depth