The effects of diabetes on the collagen structure and material properties of the sclera are unknown but may be important to elucidate whether diabetes is a risk factor for major ocular diseases such as glaucoma. This study provides a quantitative assessment of the changes in scleral stiffness and collagen fiber alignment associated with diabetes. Posterior scleral shells from five diabetic donors and seven non-diabetic donors were pressurized to 30 mm Hg. Three-dimensional surface displacements were calculated during inflation testing using digital image correlation (DIC). After testing, each specimen was subjected to wide-angle X-ray scattering (WAXS) measurements of its collagen organization. Specimen-specific finite element models of the posterior scleras were generated from the experimentally measured geometry. An inverse finite element analysis was developed to determine the material properties of the specimens, i.e., matrix and fiber stiffness, by matching DIC-measured and finite element predicted displacement fields. Effects of age and diabetes on the degree of fiber alignment, matrix and collagen fiber stiffness, and mechanical anisotropy were estimated using mixed effects models accounting for spatial autocorrelation. Older age was associated with a lower degree of fiber alignment and larger matrix stiffness for both diabetic and non-diabetic scleras. However, the age-related increase in matrix stiffness was 87% larger in diabetic specimens compared to non-diabetic controls and diabetic scleras had a significantly larger matrix stiffness (p = 0.01). Older age was associated with a nearly significant increase in collagen fiber stiffness for diabetic specimens only (p = 0.06), as well as a decrease in mechanical anisotropy for non-diabetic scleras only (p = 0.04). The interaction between age and diabetes was not significant for all outcomes. This study suggests that the age-related increase in scleral stiffness is accelerated in eyes with diabetes, which may have important implications in glaucoma.
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July 2015
Research-Article
Effects of Age and Diabetes on Scleral Stiffness
Baptiste Coudrillier,
Baptiste Coudrillier
Department of Biomedical Engineering,
e-mail: baptiste.coudrillier@bme.gatech.edu
Georgia Institute of Technology
,Atlanta, GA 30332
e-mail: baptiste.coudrillier@bme.gatech.edu
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Jacek Pijanka,
Jacek Pijanka
Structural Biophysics Group,
School of Optometry and Vision Sciences,
School of Optometry and Vision Sciences,
Cardiff University
,Cardiff CF24 4HQ, Wales
, UK
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Joan Jefferys,
Joan Jefferys
Glaucoma Center of Excellence,
Wilmer Ophthalmological Institute,
Wilmer Ophthalmological Institute,
Johns Hopkins University School of Medicine
,Baltimore, MD 21287
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Thomas Sorensen,
Thomas Sorensen
Diamond Light Source
,Didcot
,Oxfordshire OX11 0DE
, UK
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Harry A. Quigley,
Harry A. Quigley
Glaucoma Center of Excellence,
Wilmer Ophthalmological Institute,
Wilmer Ophthalmological Institute,
Johns Hopkins University School of Medicine
,Baltimore, MD 21287
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Craig Boote,
Craig Boote
Structural Biophysics Group,
School of Optometry and Vision Sciences,
School of Optometry and Vision Sciences,
Cardiff University
,Cardiff CF24 4HQ, Wales
, UK
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Thao D. Nguyen
Thao D. Nguyen
Department of Mechanical Engineering,
e-mail: vicky.nguyen@jhu.edu
Johns Hopkins University
,Baltimore, MD 21218
e-mail: vicky.nguyen@jhu.edu
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Baptiste Coudrillier
Department of Biomedical Engineering,
e-mail: baptiste.coudrillier@bme.gatech.edu
Georgia Institute of Technology
,Atlanta, GA 30332
e-mail: baptiste.coudrillier@bme.gatech.edu
Jacek Pijanka
Structural Biophysics Group,
School of Optometry and Vision Sciences,
School of Optometry and Vision Sciences,
Cardiff University
,Cardiff CF24 4HQ, Wales
, UK
Joan Jefferys
Glaucoma Center of Excellence,
Wilmer Ophthalmological Institute,
Wilmer Ophthalmological Institute,
Johns Hopkins University School of Medicine
,Baltimore, MD 21287
Thomas Sorensen
Diamond Light Source
,Didcot
,Oxfordshire OX11 0DE
, UK
Harry A. Quigley
Glaucoma Center of Excellence,
Wilmer Ophthalmological Institute,
Wilmer Ophthalmological Institute,
Johns Hopkins University School of Medicine
,Baltimore, MD 21287
Craig Boote
Structural Biophysics Group,
School of Optometry and Vision Sciences,
School of Optometry and Vision Sciences,
Cardiff University
,Cardiff CF24 4HQ, Wales
, UK
Thao D. Nguyen
Department of Mechanical Engineering,
e-mail: vicky.nguyen@jhu.edu
Johns Hopkins University
,Baltimore, MD 21218
e-mail: vicky.nguyen@jhu.edu
Manuscript received November 16, 2014; final manuscript received February 24, 2015; published online June 2, 2015. Assoc. Editor: Pasquale Vena.
J Biomech Eng. Jul 2015, 137(7): 071007 (10 pages)
Published Online: July 1, 2015
Article history
Received:
November 16, 2014
Revision Received:
February 24, 2015
Online:
June 2, 2015
Citation
Coudrillier, B., Pijanka, J., Jefferys, J., Sorensen, T., Quigley, H. A., Boote, C., and Nguyen, T. D. (July 1, 2015). "Effects of Age and Diabetes on Scleral Stiffness." ASME. J Biomech Eng. July 2015; 137(7): 071007. https://doi.org/10.1115/1.4029986
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