March 2012
Volume 53, Issue 14
ARVO Annual Meeting Abstract  |   March 2012
Loss of Elasticity in the Aging Human Sclera
Author Affiliations & Notes
  • Rafael Grytz
    Devers Eye Institute, Portland, Oregon
  • Massimo A. Fazio
    Devers Eye Institute, Portland, Oregon
  • Michael J. Girard
    Bioengineering, Imperial College London, London, United Kingdom
  • Vincent Libertiaux
    Devers Eye Institute, Portland, Oregon
  • Luigi Bruno
    Mechanical Engineering, University of Calabria, Calabria, Italy
  • Stuart Gardiner
    Devers Eye Institute, Portland, Oregon
  • Christopher A. Girkin
    Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama
  • J. Crawford Downs
    Devers Eye Institute, Portland, Oregon
  • Footnotes
    Commercial Relationships  Rafael Grytz, None; Massimo A. Fazio, None; Michael J. Girard, None; Vincent Libertiaux, None; Luigi Bruno, None; Stuart Gardiner, None; Christopher A. Girkin, None; J. Crawford Downs, None
  • Footnotes
    Support  NIH Grants R01-EY18926, R01-EY19333; Legacy Good Samaritan Foundation; EyeSight Foundation of Alabama; Research to Prevent Blindness Physician-Scientist Award
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 2800. doi:
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      Rafael Grytz, Massimo A. Fazio, Michael J. Girard, Vincent Libertiaux, Luigi Bruno, Stuart Gardiner, Christopher A. Girkin, J. Crawford Downs; Loss of Elasticity in the Aging Human Sclera. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2800.

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

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To determine the age-related alterations in the elastic response of 30 posterior scleral shells from human donors, 27-90 years old.


Posterior scleral shells were subjected to IOP elevations from 5 to 45 mmHg and the resulting full-field displacements were recorded using laser speckle interferometry. Eye-specific finite element models were generated based on experimentally measured scleral shell surface geometry and thickness. The elastic response of each scleral shell was fitted using a microstructure-based constitutive formulation, incorporating the anisotropic architecture and crimp form of scleral collagen fibrils (JMBBM 2(5):522-533, 2009). Inverse numerical analyses were performed to identify the intrinsic material and micro-structural parameters for each eye by matching model deformation predictions to experimental measurements (IOVS 50(11):5226-5237, 2009). Generalized Estimating Equation models were constructed to determine whether there was a significant effect of age on the fitted material and microstructural parameters while accounting for intra-donor correlations. The biomechanical effects of aging were predicted for a 27-year-old donor eye using the statistically derived parameters.


The scleral shear modulus (the stiffness of the ground substance) increased significantly and the collagen fibril crimp angle decreased significantly with age (p<0.001). The overall IOP-dependent collagen network strain also decreased with age in the modelled example eye (Figure).


The age-related loss of scleral elasticity is due to both a stiffer ground substance and the decreasing stretch at which the collagen fibrils uncrimp and stiffen. These changes may be due to increased collagen cross-linking and loss of the elastin-driven recoil. The loss of elasticity should lead to larger high frequency IOP fluctuations (e.g. ocular pulse amplitude) in the elderly.  

Keywords: sclera • intraocular pressure • aging 

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