Enzyme-assisted deep anterior lamellar keratoplasty-a new method of lamellar dissection-a wetlab-based pilot study

To explore the safety of a new technique of lamellar dissection, using enzymatic digestion of the corneal stroma and extracellular matrix.

This was a wetlab-based pilot study of hyaluronidase and trypsin-assisted deep anterior lamellar keratoplasty (DALK) in cadaveric human corneal tissue. Enzyme-assisted DALK was performed on 17 tissues. These underwent histologic analysis using a pneumatic dissection specimen as control. Rates of perforation and Descemet membrane (DM) exposure were recorded by clinical observation and by optical coherence tomography in selected cases. Where possible, pre- and postsurgical endothelial cell counts were obtained via specular microscopy. Two tissues from the same donor were halved, with each half soaked in a different solution (Optisol, balanced salt solution, hyaluronidase, and trypsin) for 13.5 hours to observe maximal effect.

Successful exposure of DM was achieved in 8 specimens. In the remaining 9, manual dissection was possible to a residual depth of 25 to 90 μm where measured with optical coherence tomography. Three tissues had perforation of DM, all via manual maneuvers. No deleterious effects on residual host tissue were observed by light microscopy with no significant rates of endothelial cell loss in 8 tissues in which a predissection cell count was obtainable. The 2 enzymes had differing effects on soaked specimens that were reflected intraoperatively.

Preliminary results of this ex vivo study are encouraging that enzymolysis may represent an effective innovation in DALK surgery with an acceptable safety profile. Further studies are required to refine the technique and application of the enzymes in vivo.