DALK, DSEK create different stromal cleavage planes, surgeon says

BARCELONA — The cleavage plane created when separating Descemet's membrane using the big bubble technique for deep anterior lamellar keratoplasty is different from the cleavage plane created during Descemet's stripping endothelial keratoplasty, which involves the use of a blade, according to a surgeon speaking here.

"In recent years, we have differentiated the lamellar techniques that should be used when the endothelium is unaffected and the stroma is opaque and disorganized, and those where the stroma is unaffected and the primary defect is in the endothelial layer. The former pathologies are increasingly managed by DALK (deep anterior lamellar keratoplasty) and the latter by DSEK (Descemet's stripping endothelial keratoplasty) or one of its variations," said Harminder Dua, MD, at the winter meeting of the European Society of Cataract and Refractive Surgeons.

These techniques have offered the ground for new research on the complex morphology of the endothelium-Descemet's-posterior stromal interface, with the aim of better understanding the anatomical impact of surgical maneuvers in this area.

"To find the exact location of the cleavage plane in these two techniques, we simulated the DALK and DSEK separations in cadaver eyes. Intraoperatively and postoperatively by light and electron microscopy, we examined the donor endothelium removed from donor DALK buttons, the recipient deep stroma stripped of its endothelium by big bubble technique, the donor eyes' endothelium and stroma mechanically separated, and the donor eyes' endothelium and stroma separated by big bubble," Dr. Dua said.

What appeared from these images was that a stroma separated with the big bubble technique appears different from the stroma separated with a crescent blade.

Dr. Dua proposed that, although variable, the Descemet's separation obtained with a big bubble technique leaves behind a thin layer of deep posterior stroma - the posterior stromal layer - with a distinct architecture. The posterior stromal layer binds the Descemet's to the stroma, is not populated with keratocytes and is attached to the more anterior stroma by fine strands of collagen.

"When we inject a big bubble, we separate behind the [posterior stromal layer] and not in front of it. But when we use a blade, we separate in front of it," Dr. Dua said.

The cornea, he said, "is like a book, which has two covers: the Bowman in the front and the posterior stromal layer in the back, which is fairly dense but thinner. In between, there are all these layers of collagen. The endothelium and the epithelium are the jacket, the soft cover of the book."