title: An applet to estimate the IOP-induced stress and strain within the optic nerve head.
abstract: OBJECTIVE
  The ability to predict the biomechanical response of the optic nerve head (ONH) to intraocular pressure (IOP) elevation holds great promise, yet remains elusive. The objective of this work was to introduce an approach to model ONH biomechanics that combines the ease of use and speed of analytical models with the flexibility and power of numerical models.
  
  
  METHODS
  Models representing a variety of ONHs were produced, and finite element (FE) techniques used to predict the stresses (forces) and strains (relative deformations) induced on each of the models by IOP elevations (up to 10 mm Hg). Multivariate regression was used to parameterize each biomechanical response as an analytical function. These functions were encoded into a Flash-based applet. Applet utility was demonstrated by investigating hypotheses concerning ONH biomechanics posited in the literature.
  
  
  RESULTS
  All responses were parameterized well by polynomials (R² values between 0.985 and 0.999), demonstrating the effectiveness of our fitting approach. Previously published univariate results were reproduced with the applet in seconds. A few minutes allowed for multivariate analysis, with which it was predicted that often, but not always, larger eyes experience higher levels of stress and strain than smaller ones, even at the same IOP.
  
  
  CONCLUSIONS
  An applet has been presented with which it is simple to make rapid estimates of IOP-related ONH biomechanics. The applet represents a step toward bringing the power of FE modeling beyond the specialized laboratory and can thus help develop more refined biomechanics-based hypotheses. The applet is available for use at www.ocularbiomechanics.com.
authors.affiliation: Ocular Biomechanics Laboratory, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. sigalia@upmc.edu
authors.forename: Ian A
authors.initials: IA
authors.lastname: Sigal
mesh_terms: D001696:Biomechanical Phenomena; D019295:Computational Biology; D020342:Finite Element Analysis; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008954:Models, Biological; D009798:Ocular Hypertension / Q000503:physiopathology; D009898:Optic Disk / Q000503:physiopathology*; D009901:Optic Nerve Diseases / Q000503:physiopathology*; D012590:Sclera / Q000503:physiopathology