Study of Stromal Femtosecond Laser Ablation for Deep Corneal Cut Optimization

International audienceFemtosecond laser (FL) has become a common tool in corneal surgery during the last years. The first clinical application of FL in ophthalmology was in refractive surgery for the cutting of superficial cornea flaps in transparent corneas. Recently, FL applications have been extended to penetrating and anterior or posterior lamellar corneal grafts. However, commercially available FL in ophthalmology have already shown limitations in these new applications, particularly in oedematous cornea (secondary to corneal diseases or occurring during storage by eye banks) that cause light scattering during stromal crossing. In order to improve these cuts, knowledge on the biological material, namely corneal stroma, is essential. Moreover, collagen organization of anterior corneal stroma is more compact compared to the posterior one, but the influence of these structural differences on the cut has never been studied. In this work, we compared ablation rates (ARs) in anterior and posterior human corneal stroma, isolated from the rest of the cornea by mechanical dissection in order to eliminate the scattering effect. ARs were quantified using Second Harmonic Generation microscopy. Results showed significantly higher ARs in posterior corneal stroma (+23±12% (mean±SD); P=0.0038). Previously reported limitations to cut the posterior stroma with FL can therefore not be explained by the difference in collagen organization but by the optical scattering during stromal crossing