The biomechanical model of glaucoma considers intraocular pressure-related stress and resultant strain on load bearing connective tissues of the optic nerve and surrounding peripapillary sclera as one major causative influence that effects cellular, vascular, and axonal components of the optic nerve. By this reasoning, the quantification of variations in the microstructural architecture and macromechanical response of scleral shells in glaucomatous compared to healthy populations provides an insight into any variations that exist between patient populations. While scleral shells have been tested mechanically in planar and pressure-inflation scenarios the link between the macroscopic biomechanical response and the underlying microstructure has not been determined to date. A potential roadblock to determining how the microstructure changes based on pressure is the ability to mount the spherical scleral shells in a method that does not induce unwanted stresses to the samples (for instance, in the flattening of the spherical specimens), and then capturing macroscopic and microscopic changes under pressure. Often what is done is a macroscopic test followed by sample fixation and then imaging to determine microstructural organization. We introduce a novel device and method, which allows spherical samples to be pressurized and macroscopic and microstructural behavior quantified on fully hydrated ocular specimens. The samples are pressurized and a series of markers on the surface of the sclera imaged from several different perspectives and reconstructed between pressure points to allow for mapping of nonhomogenous strain. Pictures are taken from different perspectives through the use of mounting the pressurization scheme in a gimbal that allows for positioning the sample in several different spherical coordinate system configurations. This ability to move the sclera in space about the center of the globe, coupled with an upright multiphoton microscope, allows for collecting collagen, and elastin signal in a rapid automated fashion so the entire globe can be imaged.

References

1.
Quigley
,
H. A.
, and
Broman
,
A. T.
, 2006, “
The Number of People With Glaucoma worldwide in 2010 and 2020
,”
Br. J. Ophthamol.
,
90
(
3
), pp.
262
267
.
2.
Burgoyne
,
C. F.
, and
Morrison
,
J. C.
, 2001, “
The Anatomy and Pathophysiology of the Optic Nerve Head in Glaucoma
,”
J. Glaucoma
,
10
(5 Suppl 1), pp.
S16
18
.
3.
Burgoyne
,
C. F.
,
Downs
,
J. C.
,
Bellezza
,
A. J.
,
Suh
,
J. K.
, and
Hart
,
R. T.
, 2005, “
The Optic Nerve Head as a Biomechanical Structure: A New Paradigm for Understanding the Role of IOP-Related Stress and Strain in the Pathophysiology of Glaucomatous Optic Nerve Head Damage
,”
Prog. Retin. Eye Res.
,
24
(
1
), pp.
39
73
.
4.
Ethier
,
C. R.
,
Johnson
,
M.
, and
Ruberti
,
J.
, 2004, “
Ocular Biomechanics and Biotransport
,”
Annu. Rev. Biomed. Eng.
,
6
, pp.
249
273
.
5.
Quigley
,
H. A.
,
Addicks
,
E. M.
,
Green
,
W. R.
, and
Maumenee
,
A. E.
, 1981, “
Optic Nerve Damage in Human Glaucoma. II. The Site of Injury and Susceptibility to Damage
,”
Arch. Ophthalmol. (Chicago)
,
99
(
4
), pp.
635
649
.
6.
Battaglioli
,
J. L.
, and
Kamm
,
R. D.
, 1984, “
Measurements of the Compressive Properties of Scleral Tissue
,”
Invest. Ophthalmol. Visual Sci.
,
25
(
1
), pp.
59
65
.
7.
Downs
,
J. C.
,
Suh
,
J. K.
,
Thomas
,
K. A.
,
Bellezza
,
A. J.
,
Hart
,
R. T.
, and
Burgoyne
,
C. F.
, 2005, “
Viscoelastic Material Properties of the Peripapillary Sclera in Normal and Early-Glaucoma Monkey Eyes
,”
Invest. Ophthalmol. Visual Sci.
,
46
(
2
), pp.
540
546
.
8.
Girard
,
M. J.
,
Downs
,
J. C.
,
Bottlang
,
M.
,
Burgoyne
,
C. F.
, and
Suh
,
J. K.
, 2009, “
Peripapillary and Posterior Scleral Mechanics—Part II: Experimental and Inverse Finite Element Characterization
,”
ASME J. Biomech. Eng.
,
131
(
5
), p.
051012
.
9.
Girard
,
M. J.
,
Downs
,
J. C.
,
Burgoyne
,
C. F.
, and
Suh
,
J. K.
, 2008, “
Experimental Surface Strain Mapping of Porcine Peripapillary Sclera Due to Elevations of Intraocular Pressure
,”
ASME J. Biomech. Eng.
,
130
(
4
), p.
041017
.
10.
Girard
,
M. J.
,
Suh
,
J. K.
,
Bottlang
,
M.
,
Burgoyne
,
C. F.
, and
Downs
,
J. C.
, 2009, “
Scleral Biomechanics in the Aging Monkey Eye
,”
Invest. Ophthalmol. Visual Sci.
,
50
(
11
), pp.
5226
5237
.
11.
Mortazavi
,
A. M.
,
Simon
,
B. R.
,
Stamer
,
W. D.
, and
Vande Geest
,
J. P.
, 2009, “
Drained Secant Modulus for Human and Porcine Peripapillary Sclera Using Unconfined Compression Testing
,”
Exp. Eye Res.
,
89
(
6
), pp.
892
897
.
12.
Bellezza
,
A. J.
,
Hart
,
R. T.
, and
Burgoyne
,
C. F.
, 2000, “
The Optic Nerve Head as a Biomechanical Structure: Initial Finite Element Modeling
,”
Invest. Ophthalmol. Visual Sci.
,
41
(
10
), pp.
2991
3000
.
13.
Norman
,
R. E.
,
Flanagan
,
J. G.
,
Sigal
,
I. A.
,
Rausch
,
S. M.
,
Tertinegg
,
I.
, and
Ethier
,
C. R.
, 2011, “
Finite Element Modeling of the Human Sclera: Influence on Optic Nerve Head Biomechanics and Connections With Glaucoma
,”
Exp. Eye Res
,
93
, pp.
4
12
.
14.
Edwards
,
M. E.
, and
Good
,
T. A.
, 2001, “
Use of a Mathematical Model to Estimate Stress and Strain During Elevated Pressure Induced Lamina Cribrosa Deformation
,”
Curr. Eye Res.
,
23
(
3
), pp.
215
225
.
15.
Johnson
,
D. H.
, 1996, “
Human Trabecular Meshwork Cell Survival is Dependent on Perfusion Rate
,”
Invest. Ophthalmol. Visual Sci.
,
37
(
6
), pp.
1204
1208
.
16.
Ramos
,
R. F.
, and
Stamer
,
W. D.
, 2008, “
Effects of Cyclic Intraocular Pressure on Conventional Outflow Facility
,”
Invest. Ophthalmol. Visual Sci.
,
49
(
1
), pp.
275
281
.
17.
Amabili
,
M.
, 2008,
Nonlinear Vibrations and Stability of Shells and Plates
,
Cambridge University Press
,
Cambridge
.
18.
Eberl
,
C.
, and
Thompson
,
D. S. G., R.
, 2006, “
matlab Central. In File ID: 12413
.”
19.
Keyes
,
J. T.
,
Borowicz
,
S. M.
,
Rader
,
J. H.
,
Utzinger
,
U.
,
Azhar
,
M.
, and
Vande Geest
,
J. P.
, “
Design and Demonstration of a Microbiaxial Optomechanical Device for Multiscale Characterization of Soft Biological Tissues With Two-Photon Microscopy
,”
Microsc. Microanal.
,
17
(
2
), pp.
167
175
.
20.
Lei
,
Y.
,
Overby
,
D. R.
,
Boussommier-Calleja
,
A.
,
Stamer
,
W. D.
, and
Ethier
,
C. R.
, “
Outflow Physiology of the Mouse Eye: Pressure Dependence and Washout
,”
Invest. Ophthalmol. Visual Sci.
,
52
(
3
), pp.
1865
1871
.
21.
Boyce
,
B. L.
,
Grazier
,
J. M.
,
Jones
,
R. E.
, and
Nguyen
,
T. D.
, 2008, “
Full-Field Deformation of Bovine Cornea Under Constrained Inflation Conditions
,”
Biomaterials
,
29
(
28
), pp.
3896
3904
.
22.
Myers
,
K. M.
,
Cone
,
F. E.
,
Quigley
,
H. A.
,
Gelman
,
S.
,
Pease
,
M. E.
, and
Nguyen
,
T. D.
, “
The In Vitro Inflation Response of Mouse Sclera
,”
Exp. Eye Res.
,
91
(
6
), pp.
866
875
.
23.
Winkler
,
M.
,
Jester
,
B.
,
Nien-Shy
,
C.
,
Massei
,
S.
,
Minckler
,
D. S.
,
Jester
,
J. V.
, and
Brown
,
D. J.
, “
High Resolution Three-Dimensional Reconstruction of the Collagenous Matrix of the Human Optic Nerve Head
,”
Brain Res. Bull.
,
81
(
2–3
), pp.
339
348
.
24.
Agopov
,
M.
,
Lomb
,
L.
,
La Schiazza
,
O.
, and
Bille
,
J. F.
, 2009, “
Second Harmonic Generation Imaging of the Pig Lamina Cribrosa Using a Scanning Laser Ophthalmoscope-Based Microscope
,”
Lasers Med. Sci.
,
24
(
5
), pp.
787
792
.
25.
Brown
,
D. J.
,
Morishige
,
N.
,
Neekhra
,
A.
,
Minckler
,
D. S.
, and
Jester
,
J. V.
, 2007, “
Application of Second Harmonic Imaging Microscopy to Assess Structural Changes in Optic Nerve Head Structure Ex Vivo
,”
J. Biomed. Opt.
,
12
(
2
), p.
024029
.
26.
Yan
,
D.
,
McPheeters
,
S.
,
Johnson
,
G.
,
Utzinger
,
U.
, and
Vande Geest
,
J. P.
, “
Microstructural Differences in the Human Posterior Sclera as a Function of Age and Race
,”
Invest. Ophthalmol. Visual Sci.
,
52
(
2
), pp.
821
829
.
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