title: Cell viability and shock wave amplitudes in the endothelium of porcine cornea exposed to ultrashort laser pulses.
abstract: OBJECTIVE
  Some forms of keratoplasty assisted by ultrashort-pulse lasers require performing laser cuts close to the endothelium, which requires the knowledge of "safe" values concerning incision depth and pulse energy preserving endothelial cell viability. Our study aims to determine the thresholds for cell death in porcine corneas exposed to ultrashort laser pulses, in terms of laser pulse energy and nearness of the impacts to the endothelium.
  
  
  METHODS
  Using a laboratory laser set-up, lamellar cuts were induced while varying pulse energies and distances from the endothelium. A fluorescent staining protocol was used to determine the percentage of surviving endothelial cells. Numerical simulations of the Euler equations for compressible fluids provided pressure level and axial and radial pressure gradient estimates at the endothelium.
  
  
  RESULTS
  Ninety percent of the endothelial cells survived when using 16.5 μJ pulses no closer than 200 μm to the endothelium, or pulses not exceeding 2 μJ at a distance of 50 μm. The comparison of the observed percentage of surviving cells with the estimates of the shock wave amplitudes and gradients generated by the laser pulses yielded cell death thresholds at amplitudes in the megapascal range, or gradients of the order of 108Pa/m.
  
  
  CONCLUSIONS
  Our results provide limits in terms of pulse energy and distance of the incision from the endothelium within which endothelial cell viability is preserved. Current forms of corneal laser surgery are compatible with these limits. However, these limits will need to be considered for the development of future laser routines working in close proximity to the endothelium.
authors.affiliation: LOA, ENSTA-ParisTech, École Polytechnique, CNRS, Université Paris-Saclay, 828 bd des Maréchaux, F-91762, Palaiseau, France.
authors.forename: Syed Asad
authors.initials: SA
authors.lastname: Hussain
authors.affiliation: Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay, F-91128, Palaiseau, France.
authors.forename: Carles
authors.initials: C
authors.lastname: Milián
authors.affiliation: LOA, ENSTA-ParisTech, École Polytechnique, CNRS, Université Paris-Saclay, 828 bd des Maréchaux, F-91762, Palaiseau, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Crotti
authors.affiliation: LOA, ENSTA-ParisTech, École Polytechnique, CNRS, Université Paris-Saclay, 828 bd des Maréchaux, F-91762, Palaiseau, France.
authors.forename: Laura
authors.initials: L
authors.lastname: Kowalczuk
authors.affiliation: LOA, ENSTA-ParisTech, École Polytechnique, CNRS, Université Paris-Saclay, 828 bd des Maréchaux, F-91762, Palaiseau, France.
authors.forename: Fatima
authors.initials: F
authors.lastname: Alahyane
authors.affiliation: LOA, ENSTA-ParisTech, École Polytechnique, CNRS, Université Paris-Saclay, 828 bd des Maréchaux, F-91762, Palaiseau, France.
authors.forename: Zacaria
authors.initials: Z
authors.lastname: Essaïdi
authors.affiliation: Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay, F-91128, Palaiseau, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Couairon
authors.affiliation: LOB, École polytechnique, CNRS, Inserm 1182, Université Paris-Saclay, F-91128, Palaiseau, France.
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Schanne-Klein
authors.affiliation: LOA, ENSTA-ParisTech, École Polytechnique, CNRS, Université Paris-Saclay, 828 bd des Maréchaux, F-91762, Palaiseau, France. Karsten.Plamann@ensta-paristech.fr.
authors.forename: Karsten
authors.identifier: http://orcid.org/0000-0002-8254-2158
authors.initials: K
authors.lastname: Plamann
mesh_terms: D000818:Animals; D016923:Cell Death; D002470:Cell Survival; D048988:Corneal Surgery, Laser / Q000379:methods*; D004728:Endothelium, Corneal / Q000601:surgery / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D023421:Models, Animal; D013552:Swine; D041623:Tomography, Optical Coherence
keywords: Cell viability; Cornea; Endothelium; Keratoplasty; Laser surgery; Ultrashort pulse