From our podcast yesterday, we explore the surgical pearls for preparing a Pre-Descemet’s Endothelial Keratoplasty (PDEK) graft using the refined technique pioneered by Dr. Dinh and Dr. Kalinnikov. While DMEK (originally described by the brilliant Dr Amar Agarwal) remains a great option, PDEK offers a more robust graft by including the Dua’s Layer, making it less prone to tearing and easier to handle in complex eyes. Plus we have a bonus video of a pinhole pupilloplasty with the pupil size gauge being used to be precise. This topic was also covered in the CataractCoach Podcast (the top podcast in all of ophthalmology).
Key steps for PDEK graft preparation:
1. . Mounting, stabilization, big bubble type 1 formation
- Place the scleral–corneal disc on a special PDEK base with the endothelium facing up
- Secure it with 4 needles and bend them for better stability
- Apply trypan blue to improve visualization
- Insert a 30G needle connected to 5 ml syringe with spring loaded plunger from the peripheral cornea toward the mid-center
- Position a ring fixator over the cornea
- Inject air to create a Type 1 big bubble (initially ~5.5 mm)
2. Bubble enlargement
- Inject conservative medium to expand the bubble to ~7–8 mm (desired graft size)
3. Staining and opening
- Puncture the bubble with a crescent knife
- Inject trypan blue inside the big bubble
4. Graft creation
- Cut along the bubble edge with scissors to isolate the PDEK graft
5. Final handling
- Transfer the prepared graft into a Geuder tube for further use
PDEK is an excellent option for younger donors or cases where the endothelium is fragile. Mastering this preparation technique is a vital skill for any modern cornea surgeon.
PDEK vs. DMEK: A Surgical Comparison
While both are endothelial keratoplasty techniques, they differ significantly in graft thickness and handling characteristics.
| Feature | DMEK: Descemet Membrane | PDEK: Pre-Descemet’s EK |
| Graft Composition | Descemet’s Membrane + Endothelium | Dua’s Layer + DM + Endothelium |
| Graft Thickness | Very thin (~10-15 microns) | Thicker (~25-30 microns) |
| Donor Age | Prefer older donors (easier peeling) | Can use very young donors |
| Ease of Handling | Prone to tight scrolling and tearing | More “memory”; easier to unfold |
| Preparation Method | Manual peeling | “Big Bubble” air dissection |
| Visual Outcomes | Excellent; near-perfect anatomy | Comparable to DMEK |
| Risk of Tearing | Higher during preparation | Lower due to Dua’s Layer strength |
