title: Changes in custom biomechanical variables after femtosecond laser in situ keratomileusis and photorefractive keratectomy for myopia.
abstract: To analyze changes in new biomechanical descriptors with myopic femtosecond laser-assisted laser in situ keratomileusis (LASIK), compare them with the biomechanical response after photorefractive keratectomy (PRK) with similar levels of myopic ablation, and evaluate correlations between changes in custom variables and biomechanically relevant variables.
  
  
  
  Cleveland Clinic, Cleveland, Ohio, USA.
  
  
  
  Cohort study.
  
  
  
  Custom biomechanical variables from the Optical Response Analyzer were assessed preoperatively and 1 and 3 months postoperatively. Differences between preoperative values and postoperative values were determined. Intraindividual change (preoperative value minus postoperative value) was calculated and compared with changes after PRK. The correlation of the change in each custom biomechanical variable with the preoperative central corneal thickness, residual stromal bed tissue ablated, and percentage of tissue depth altered was also studied.
  
  
  
  The study enrolled 156 eyes of 156 consecutive patients. Fifteen variables changed significantly after femtosecond myopic LASIK and were stable postoperatively because no significant difference was shown between 1-month values and 3-month values. Comparison of the changes in biomechanical variables between LASIK and PRK eyes showed no significant differences. Surgical changes in several custom biomechanical variables correlated with the percentage of tissue depth altered.
  
  
  
  The results provide the first reference values for a more comprehensive panel of indicators of the biomechanical response to myopic LASIK and PRK. Changes in custom variables reflected a consistent decrease in corneal biomechanical resistance to deformation after myopic femtosecond LASIK and PRK. For comparable attempted corrections, biomechanical changes were comparable between femtosecond laser-assisted LASIK and PRK.
  
  
  
  Proprietary or commercial disclosures are listed after the references.
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil. Electronic address: marconysanthiago@hotmail.com.
authors.forename: Marcony R
authors.initials: MR
authors.lastname: Santhiago
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Wilson
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: Katie M
authors.initials: KM
authors.lastname: Hallahan
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: David
authors.initials: D
authors.lastname: Smadja
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: Michelle
authors.initials: M
authors.lastname: Lin
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: Renato
authors.initials: R
authors.lastname: Ambrosio
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: Vivek
authors.initials: V
authors.lastname: Singh
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: Abhjit
authors.initials: A
authors.lastname: Sinha Roy
authors.affiliation: From Cole Eye Institute (Santhiago, Wilson, Hallahan, Smadja, Lin, Singh, Roy, Dupps) and the Department of Biomedical Engineering (Dupps), Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA; the Departments of Ophthalmology, University São Paulo (Santhiago), Sao Paulo, Federal University of São Paulo (Ambrosio), São Paulo, and the Federal University of Rio de Janeiro (Santhiago), Rio de Janeiro, Brazil.
authors.forename: William J
authors.initials: WJ
authors.lastname: Dupps
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D003315:Cornea / Q000503:physiopathology*; D063171:Corneal Pachymetry; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011446:Prospective Studies
references.citation: J Refract Surg. 2008 Jan;24(1):S85-9
references.pmid: 18269156
references.citation: J Cataract Refract Surg. 2005 Jan;31(1):156-62
references.pmid: 15721708
references.citation: Invest Ophthalmol Vis Sci. 2007 Jul;48(7):3026-31
references.pmid: 17591868
references.citation: J Refract Surg. 2001 Nov-Dec;17(6):658-69
references.pmid: 11758984
references.citation: J Cataract Refract Surg. 2008 Dec;34(12):2049-56
references.pmid: 19027558
references.citation: Cornea. 2012 Feb;31(2):198-205
references.pmid: 22157568
references.citation: Am J Ophthalmol. 2009 Jun;147(6):966-72, 972.e1
references.pmid: 19327748
references.citation: J Refract Surg. 2006 Nov;22(9):861-70
references.pmid: 17124880
references.citation: Prog Retin Eye Res. 2001 Sep;20(5):625-37
references.pmid: 11470453
references.citation: J Refract Surg. 2006 Nov;22(9):851-60
references.pmid: 17124879
references.citation: J Refract Surg. 2007 Nov;23(9):880-7
references.pmid: 18041240
references.citation: J Cataract Refract Surg. 2008 Nov;34(11):1886-91
references.pmid: 19006734
references.citation: J Cataract Refract Surg. 2010 Jun;36(6):947-53
references.pmid: 20494766
references.citation: Ophthalmology. 2010 Apr;117(4):673-9
references.pmid: 20138369
references.citation: Invest Ophthalmol Vis Sci. 2010 May;51(5):2403-10
references.pmid: 19907025
references.citation: J Biomech Eng. 2011 Jan;133(1):011002
references.pmid: 21186892
references.citation: Invest Ophthalmol Vis Sci. 1991 Jul;32(8):2244-58
references.pmid: 2071337
references.citation: Exp Eye Res. 2006 Oct;83(4):709-20
references.pmid: 16720023
references.citation: J Cataract Refract Surg. 2008 Mar;34(3):510-3
references.pmid: 18299080
references.citation: J Refract Surg. 2009 Oct;25(10):875-87
references.pmid: 19835328
references.citation: J Cataract Refract Surg. 2009 Oct;35(10):1774-88
references.pmid: 19781475
references.citation: Ophthalmology. 2014 Feb;121(2):459-68
references.pmid: 24289916