Reshaping and customization of SMILE-derived biological lenticules for intrastromal implantation

Abstract

Purpose: To evaluate the feasibility of excimer laser reshaping of biological lenticules available after small incision lenticule extraction (SMILE). Methods: Fresh and cryopreserved SMILE-derived human lenticules underwent excimer laser ablation for stromal reshaping. The treatment effects in the lasered group were compared with the nonlasered group with respect to changes in surface functional groups (by Fourier transform infrared spectroscopy [FTIR]) and surface morphology (by scanning electron microscopy [SEM] and atomic force microscopy [AFM]). Ten SMILE-derived porcine lenticules, five nonlasered (107-μm thick, −6 diopter [D] spherical power) and five excimer lasered (50% thickness reduction), were implanted into a 120-μm stromal pocket of 10 porcine eyes. Corneal thickness and topography were assessed before and after implantation. Results: FTIR illustrated prominent changes in the lipid profile. The collagen structure was also affected by the laser treatment but to a lesser extent. SEM exhibited a more regular surface for the lasered lenticules, confirmed by the lower mean Rz value (290.1 ± 96.1 nm vs. 380.9 ± 92.6 nm, P = 0.045) on AFM. The lasered porcine lenticules were thinner than the nonlasered controls during overhydration (132 ± 26 μm vs. 233 ± 23 μm, P < 0.001) and after 5 hours in a moist chamber (46 ± 3 μm vs. 57 ± 3 μm, P < 0.001). After implantation, the nonlasered group showed a tendency toward a greater increase in axial keratometry (6.63 ± 2.17 D vs. 5.60 ± 3.79 D, P = 0.613) and elevation (18.6 ± 15.4 vs. 15.2 ± 5.5, P = 0.656) than the lasered group. Conclusions: Excimer laser ablation may be feasible for thinning and reshaping of SMILE-derived lenticules before reimplantation or allogenic transplantation. However, controlled lenticule dehydration before ablation is necessary in order to allow stromal thinning.