Atomic Force Microscopy and Scanning Electron Microscopy for Characterization of Interface Surface Roughness After ELITA Femtosecond Laser Treatments.

Purpose: To characterize and compare the corneal interface surface roughness of the ELITA femtosecond laser flap and smooth incision lenticular keratomileusis (SILK) to the iFS femtosecond laser flap with atomic force microscopy (AFM) and scanning electron microscopy (SEM). Methods: The iFS flap with 700 nJ pulse energy, ELITA flap with 50 nJ, and ELITA SILK with 50 nJ were performed on a total of 12 ex vivo porcine eyes. After laser treatment and mechanical separation, the posterior surface of the laser-treated interface was trephined, fixated, and dehydrated. The corneal interface surface roughness was assessed with AFM in contact mode. For AFM, 15 eye locations (three eyes, 5 locations each) for each treatment were evaluated with a 20 × 20-µm scanning area and 512 × 512-pixel resolution. The root mean square (RMS) roughness for each treatment method was measured. With SEM, representative images were taken with 100× and 250× magnification. Results: The RMS roughness of the iFS flap, ELITA flap, and ELITA SILK was 236 ± 64 nm, 114 ± 33 nm, and 203 ± 84 nm, respectively. ELITA flap interface surface roughness was significantly less than that of the iFS flap (P < 0.001) and ELITA SILK (P < 0.001). Conclusions: The ELITA flap produced a smoother corneal interface surface compared to the iFS flap and ELITA SILK, while the iFS flap and ELITA SILK produced similar corneal interface surface roughness. Translational Relevance: This study suggests that the ELITA femtosecond laser's ability to create smoother corneal interfaces may enhance visual acuity recovery time.