title: Spatially heterogeneous corneal mechanical responses before and after riboflavin-ultraviolet-A crosslinking.
abstract: OBJECTIVE
  To determine the heterogeneous through-thickness strains in the cornea at physiologic intraocular pressures before and after corneal collagen crosslinking (CXL) using noninvasive ultrasound.
  
  
  METHODS
  Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Sixteen paired canine corneoscleral shells were divided into 2 groups. The CXL group completed a standard CXL protocol using riboflavin-ultraviolet-A (UVA) irradiation. The control group was given an identical treatment except UVA irradiation. Ultrasound scans (at 55 MHz) of the cornea were obtained before and after treatment as the corneoscleral shell was inflated from 5 mm Hg to 45 mm Hg to calculate the distributive through-thickness strains in the cornea. The mean radial and tangential strains of the whole cornea layer, as well as those of the anterior, middle, and posterior thirds of the cornea, were compared before and after treatment in the control group and CXL group using linear mixed models with repeated measures.
  
  
  RESULTS
  Significant reductions in tangential and radial strains occurred in the CXL group (P=.003 and P=.0025, respectively) but not the control group (P=.08 and P=.63, respectively). The anterior third had the smallest strains in all pretreated corneas (P<.001) and posttreated corneas (CXL group, P=.023; control group, P=.01).
  
  
  CONCLUSIONS
  Ultrasound speckle tracking showed heterogeneous strain distributions through the cornea and confirmed that CXL results in a stiffer corneal response (ie, smaller strains during physiologic loadings). This technique may provide a clinical tool to quantify the biomechanical effects of CXL.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the College of Medicine (Palko), the Department of Biomedical Engineering (Tang, Perez, Liu), the Center for Biostatistics (Pan), and the Department of Ophthalmology (Liu), Ohio State University, Columbus, Ohio, USA.
authors.forename: Joel R
authors.initials: JR
authors.lastname: Palko
authors.affiliation: From the College of Medicine (Palko), the Department of Biomedical Engineering (Tang, Perez, Liu), the Center for Biostatistics (Pan), and the Department of Ophthalmology (Liu), Ohio State University, Columbus, Ohio, USA.
authors.forename: Junhua
authors.initials: J
authors.lastname: Tang
authors.affiliation: From the College of Medicine (Palko), the Department of Biomedical Engineering (Tang, Perez, Liu), the Center for Biostatistics (Pan), and the Department of Ophthalmology (Liu), Ohio State University, Columbus, Ohio, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Cruz Perez
authors.affiliation: From the College of Medicine (Palko), the Department of Biomedical Engineering (Tang, Perez, Liu), the Center for Biostatistics (Pan), and the Department of Ophthalmology (Liu), Ohio State University, Columbus, Ohio, USA.
authors.forename: Xueliang
authors.initials: X
authors.lastname: Pan
authors.affiliation: From the College of Medicine (Palko), the Department of Biomedical Engineering (Tang, Perez, Liu), the Center for Biostatistics (Pan), and the Department of Ophthalmology (Liu), Ohio State University, Columbus, Ohio, USA. Electronic address: liu.314@osu.edu.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
mesh_terms: D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology*; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004285:Dogs; D004548:Elasticity / Q000502:physiology; D007429:Intraocular Pressure / Q000502:physiology; D033401:Microscopy, Acoustic; D017319:Photosensitizing Agents / Q000494:pharmacology*; D012256:Riboflavin / Q000494:pharmacology*; D013314:Stress, Mechanical; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin
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