Atomic Force Microscopy for the Evaluation of Corneal Surface Roughness after Femtosecond Laser Flap Creation and Excimer Ablation.

Abstract

Introduction: It is well known that the femtosecond laser lamellar cut has some degree of roughness. Nevertheless, as in femtosecond laser assisted LASIK (FS-LASIK), an excimer LASIK ablation is performed, the post-ablation stromal bed should show a marked decrease in roughness. We decided to compare, using atomic force microscopy (AFM), the roughness of the corneal stromal bed, after a Femtosecond lasers device (FS) flap was created with or without an excimer myopic ablation.Methods: Using 6 freshly enucleated porcine eyes, we created in every eye a flap using a femtosecond laser. Additionally in 3 eyes an excimer laser ablation to correct -3 diopters (D) was made. AFM imaging of the remaining corneal stroma was performed. Ten different square areas of 20μm x 20μm at the central area of the stroma of each corneal sample were studied. The roughness parameters used was the root-mean-square (RMS) deviation from a perfectly flap plane.Results: The RMS deviation were 360 ± 120 nm in femtosecond laser only, and 110 ± 20 nm in those cases where excimer is also involved (p<0.0001).Conclusions: Our results show that the roughness of the surface treated with excimer is clearly lower than in the group with no excimer ablation, thus the application of laser excimer after a flap creation by femtosecond laser flap creation may soften the nano-irregularities created by this technique.