Histologic evaluation of human posterior lamellar discs for femtosecond laser Descemet's stripping endothelial keratoplasty.

ABSTRACT

PURPOSE: To evaluate the histologic changes in corneal structure after femtosecond laser preparation of posterior lamellar discs, more specifically, the smoothness of the stromal bed and the accuracy of the predicted depth of the horizontal lamellar cut. MATERIALS AND METHODS: Nineteen human donor eyes unsuitable for transplantation were used. Femtosecond laser was used to prepare a horizontal lamellar cut in donor corneas at a depth of 400 microm. Transmission electron microscopy images were used to evaluate the changes in the corneal structure and to measure the damage zone. Scanning electron microscopy images were used to determine the relative depth of the horizontal lamellar cut, and the stromal bed was examined to determine the smoothness of the surface. RESULTS: Transmission electron microscopy images showed a mean damage zone of 6.8 +/- 3.1 microm, which consisted of irregularly oriented collagen fibrils and electron-dense granular material. The collagen lamellae, both anteriorly and posteriorly of the damaged zone, showed a regular parallel configuration. The relative depth of the horizontal lamellar cut as percentage of the total corneal thickness in the center and periphery was 70.4% +/- 4.5% and 55.6% +/- 5.9%. Scanning electron microscopy images of the stromal bed showed a relatively smooth surface. CONCLUSION: The femtosecond laser is effective to prepare a deep horizontal lamellar cut in a standardized method. The stromal bed is smooth and without extensive adjacent tissue damage. The is thinner in the center and thicker at the edges, which may produce a mild hyperopic shift after femtosecond laser-assisted Descemet's stripping endothelial keratoplasty.