Dual Laser-Assisted Lamellar Anterior Keratoplasty: A Laboratory Study in Eye Bank Eyes

Abstract

Purpose: : To develop a dual laser-assisted lamellar anterior keratoplasty (LALAK) technique, using excimer and femtosecond lasers to perform surgery on eye-bank eyes.

Methods: : First we compared interface surfaces produced by deep excimer ablation, femtosecond lamellar cuts, and manual lamellar dissection, and evaluated the effect of excimer smoothing with fluid masking on each surface. Masked observers graded scanning electron microscopy (SEM) images of each surface on a 5-point roughness scale.Then we performed a 6-mm diameter phototherapeutic keratectomy (PTK) ablation on eye-bank corneas to a residual thickness of 200µm, followed by excimer smoothing. We used the femtosecond laser to cut donor buttons in a modified top-hat design with a thin tapered brim, which fitted into a manually dissected circumferential pocket at the base of the recipient bed. Fourier-domain optical coherence tomography (OCT) was used to measure corneal pachymetry, plan ablation depth, and evaluate results.

Results: : Deep excimer ablation with smoothing (n=4) produced a significantly (p<0.05) smoother surface (grade=3.5) than deep excimer alone (n=4, grade=3.8) or manual dissection with (n=1, grade=3.8) and without smoothing (n=1, grade=4.8). Deep femtosecond stromal cuts (n=2) produced macroscopic concentric ridges on the stromal bed surface. Four recipients underwent deep excimer ablation and 4 donors were cut with the femtosecond laser. Good peripheral graft-host match and smooth anterior contour was observed on FD-OCT imaging.

Conclusions: : These preliminary studies show that the dual LALAK technique permits improvements in interface smoothness and graft edge matching. Clinical trials are needed to determine whether improved interface smoothness can translate to better visual outcomes.

Keywords: cornea: clinical science • laser • transplantation