June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
Scleral anisotropy and its effects on the optic nerve head biomechanics
Author Affiliations & Notes
  • Thao Nguyen
    Mechanical Engineering, The Johns Hopkins University, Baltimore, MD
  • Baptiste Coudrillier
    Mechanical Engineering, The Johns Hopkins University, Baltimore, MD
  • Harry Quigley
    Wilmer Ophthalmological Institute, The Johns Hopkins University, School of Medicine, Baltimore, MD
  • Craig Boote
    Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
  • Footnotes
    Commercial Relationships Thao Nguyen, None; Baptiste Coudrillier, None; Harry Quigley, Sensimed (C), Genetech (C), Merck (C), Sucampo (C); Craig Boote, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 55. doi:https://doi.org/
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Thao Nguyen, Baptiste Coudrillier, Harry Quigley, Craig Boote; Scleral anisotropy and its effects on the optic nerve head biomechanics. Invest. Ophthalmol. Vis. Sci. 2013;54(15):55. doi: https://doi.org/.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract
 
Purpose
 

To determine the effects of the collagen fiber structure of the sclera on the mechanical response of the sclera and the optic nerve head (ONH)

 
Methods
 

Specimen-specific inverse finite element models were developed to calculate the material properties of two normal human sclera (age 67, 71) subjected to inflation testing. A distributed fiber model incorporating wide-angle X-ray scattering (WAXS) measurements of the collagen structure was applied to describe the anisotropic elastic behavior of the sclera. The material parameters were used for micromechanical studies of the mechanical anisotropy at various length scales (0.5, 2, and 4 mm). The effects of the sclera fiber structure on the ONH mechanical response were evaluated by progressively filtering out local anisotropic features (Fig. 2).

 
Results
 

The collagen structure of the midposterior sclera (MPS) showed large variations in the preferred fiber direction and degree of fiber alignment. The mechanical anisotropy of the MPS decreased with increasing length scale (Fig. 1). At the 4 mm length scale, the MPS was nearly isotropic. The anisotropy of the MPS had little effect on the mechanical response of the ONH. Modeling 71% of the MPS as isotropic caused minimal changes (< 1%) to the scleral canal expansion and posterior lamina bowing (Fig. 2, second row). In the peripapillary sclera (PPS), collagen fibers were circumferentially aligned with spatially heterogeneous degree of alignment. The deformation of the ONH was acutely sensitive to the spatially heterogeneous anisotropy of the PPS.

 
Conclusions
 

Alterations in the degree of fiber alignment within the PPS observed in glaucoma eyes (Pijanka et al., IOVS, 2012) may significantly impact the biomechanical environment of the ONH.

 
 
Map of the anisotropic ratio at the 0.5 mm (a) and the 2 mm (b) length scale. The anisotropic ratio (AR) was calculated in finite element (FE) simulations of the strain response to an applied 21 kPa equibiaxial tension for a model of square section. AR=1 for an isotropic tissue.
 
Map of the anisotropic ratio at the 0.5 mm (a) and the 2 mm (b) length scale. The anisotropic ratio (AR) was calculated in finite element (FE) simulations of the strain response to an applied 21 kPa equibiaxial tension for a model of square section. AR=1 for an isotropic tissue.
 
 
First row: A white square represents a WAXS measurement for which the anisotropic ratio was below the threshold indicated on top of the figure. The corresponding area of the sclera was modeled as isotropic in the FE model of an inflation at 30 mmHg. Second row: Evolution of the posterior deformation of the LC and scleral canal expansion as the sclera becomes more isotropic. The star corresponds to the isotropic model.
 
First row: A white square represents a WAXS measurement for which the anisotropic ratio was below the threshold indicated on top of the figure. The corresponding area of the sclera was modeled as isotropic in the FE model of an inflation at 30 mmHg. Second row: Evolution of the posterior deformation of the LC and scleral canal expansion as the sclera becomes more isotropic. The star corresponds to the isotropic model.
 
Keywords: 708 sclera • 568 intraocular pressure  
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×