Study of stromal femtosecond laser ablation for deep corneal cut optimization

Abstract

AbstractPurpose Anterior and posterior stroma of human cornea present different biophysical characteristics, the later being more hydrated and collagen fibers less tightly packed. Our aim was to investigate interactions between femtosecond laser (FL) and stroma according to the depth of cut in order to optimize FL endothelial graft preparationMethods organ cultured human corneas were prepared with a mechanical microkeratome (Moria, France) by a lamellar cut from anterior side at two different depths: 50µm for the study of anterior stroma and 350µm for the study of posterior stroma. Grooves were then performed in the remaining anterior or posterior stroma with a 800nm, 150fs FL (Thales, France) with different processing configurations (Speed: 1900 to 10000µm/s; Power: 0.8 to 6mW). After treatment, corneas were observed by light and second harmonic generation (SHG) microscopy to compare ablation rates (AR) (in µm/pulse) and cut quality in anterior and posterior stromaResults Preliminary results (n=4 corneas) showed no significant differences between posterior stroma AR (1.97±0.91µm/pulse) and anterior stroma AR (1.73±0.50µm/pulse). Using SHG microscopy, two different cutting types (with or without disruption) occurred, depending on processing configurations and independently of depth in the stromaConclusion These results suggest that there is no significant difference of AR between anterior and posterior stroma. Consequently, difficulties usually encountered to cut endothelial grafts with FL may not directly depend on a particular ablation rate of the posterior human corneal stroma, but rather on the optical scattering when FL passes through the stromal layers, already identify as a limiting factor