title: Comparison of biomechanical effects of small-incision lenticule extraction and laser in situ keratomileusis: finite-element analysis.
abstract: OBJECTIVE
  To theoretically compare the corneal stress distribution of laser in situ keratomileusis (LASIK) with the stress distribution of small-incision lenticule extraction.
  
  
  METHODS
  Cleveland Clinic Cole Institute, Cleveland, and The Ohio State University, Columbus, Ohio, USA.
  
  
  METHODS
  Computational modeling study.
  
  
  METHODS
  A finite-element anisotropic collagen fiber-dependent model of myopic surgery using patient-specific corneal geometry was constructed for LASIK, small-incision lenticule extraction, and a geometry analog model with unaltered material properties from preoperative but with postoperative geometry including thickness. Surgical parameters, magnitude of myopic correction, LASIK flap thickness, and lenticule depth in small-incision lenticule extraction were varied. Two sets of models, 1 with uniform and 1 with depth-dependent material properties, were constructed.
  
  
  RESULTS
  Stress distribution between small-incision lenticule extraction simulations and the geometry analog model were similar. In contrast, LASIK consistently reduced stress in the flap and increased stress in the residual stromal bed (RSB) compared with the geometry analog model. An increase in flap thickness or lenticule depth resulted in a greater increase in RSB stress in the LASIK model than in the small-incision lenticule extraction model.
  
  
  CONCLUSIONS
  Small-incision lenticule extraction may present less biomechanical risk to the residual bed of susceptible corneas than comparable corrections involving LASIK flaps. Deeper corrections in the stroma may be possible in small-incision lenticule extraction without added risk for ectasia.
  
  
  BACKGROUND
  Proprietary or commercial disclosures are listed after the references.
authors.affiliation: From the Cole Eye Institute (Sinha Roy, Dupps), Cleveland Clinic Foundation, the Department of Biomedical Engineering (Dupps), Lerner Research Institute, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, and the Departments of Ophthalmology and Biomedical Engineering (Roberts), The Ohio State University, Columbus, Ohio, USA.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Sinha Roy
authors.affiliation: From the Cole Eye Institute (Sinha Roy, Dupps), Cleveland Clinic Foundation, the Department of Biomedical Engineering (Dupps), Lerner Research Institute, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, and the Departments of Ophthalmology and Biomedical Engineering (Roberts), The Ohio State University, Columbus, Ohio, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Dupps
authors.affiliation: From the Cole Eye Institute (Sinha Roy, Dupps), Cleveland Clinic Foundation, the Department of Biomedical Engineering (Dupps), Lerner Research Institute, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, and the Departments of Ophthalmology and Biomedical Engineering (Roberts), The Ohio State University, Columbus, Ohio, USA. Electronic address: roberts.8@osu.edu.
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Roberts
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D003319:Corneal Stroma / Q000503:physiopathology* / Q000601:surgery; D019781:Corneal Topography; D004548:Elasticity / Q000502:physiology*; D020342:Finite Element Analysis; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008962:Models, Theoretical; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D013314:Stress, Mechanical; D013524:Surgical Flaps