title: Finite element analysis of blunt foreign body impact on the cornea after PRK and LASIK.
abstract: OBJECTIVE
  To investigate the effect of blunt foreign body impact on a human cornea after photorefractive keratectomy (PRK) and LASIK using a simulation model.
  
  
  METHODS
  Computational simulations were performed using a finite element analysis program (LS-Dyna, Livermore Software Technology Corp). The blunt foreign body was set to impact at the center of the corneal surface models (after PRK and LASIK) with thicknesses of 500, 450, 400, 350, and 300 μm. Corneal rupture was assumed to occur at a peak stress of 9.45 MPa and at a strain of 18%. The foreign body projectile was blunt in shape, made from aluminum, contained plastic-kinematic properties, and had a density of 2700 kg/m(3).
  
  
  RESULTS
  The projectile was launched at the center of the cornea with velocities ranging from 20 to 60 m/s. The threshold of impact velocities creating rupture in corneal thicknesses of 500, 450, 400, 350, and 300 μm were 33, 32.8, 30.7, 27.9, and 22.8 m/s, respectively, in the PRK model. In the LASIK model, the thresholds creating rupture in the stromal bed of the corneas with thicknesses of 500, 450, 400, 350, and 300 μm were 40, 38.1, 35.6, 31.5, and 26.7 m/s, respectively. The 110-μm corneal flap in the LASIK model ruptured at all velocities.
  
  
  CONCLUSIONS
  Ruptures occurred at lower velocities in the PRK cornea model than in the corneal stromal bed of the LASIK model following blunt foreign body impact.
authors.affiliation: Vanak Eye Surgery Center, Tehran, Iran.
authors.forename: Seyed Jamaleddin
authors.initials: SJ
authors.lastname: Mousavi
authors.forename: Nariman
authors.initials: N
authors.lastname: Nassiri
authors.forename: Nafiseh
authors.initials: N
authors.lastname: Masoumi
authors.forename: Nader
authors.initials: N
authors.lastname: Nassiri
authors.forename: Mercede
authors.initials: M
authors.lastname: Majdi-N
authors.forename: Solmaz
authors.initials: S
authors.lastname: Farzaneh
authors.forename: Ali R
authors.initials: AR
authors.lastname: Djalilian
authors.forename: Gholam A
authors.initials: GA
authors.lastname: Peyman
mesh_terms: D003198:Computer Simulation; D003315:Cornea / Q000601:surgery; D065306:Corneal Injuries; D005131:Eye Injuries / Q000209:etiology*; D020342:Finite Element Analysis; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use; D018903:Photorefractive Keratectomy; D012421:Rupture; D013524:Surgical Flaps; D013529:Surgical Wound Dehiscence / Q000209:etiology*; D014949:Wounds, Nonpenetrating / Q000209:etiology*