Racioethnic Differences in Human Posterior Scleral and Optic Nerve Stump Deformation

Tamimi, Ehab; Pyne, Jeffrey D.; Muli, Dominic K.; Axman, Katelyn F.; Howerton, Stephen J.; Davis, Matthew; Girkin, Christopher A.; Geest, Jonathan P. Vande

doi:10.1167/iovs.17-22141

Cited by 11 publications

(7 citation statements)

References 50 publications

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“… 32 Fourth, the subjects in the present study were all Koreans, and it is well-known that the biomechanical properties of the ONH can differ by race; thus, the present findings cannot be generalized to other ethnicities. 33 , 34 Last, the present study included only healthy childhood eyes, and so its findings cannot be extrapolated to glaucoma pathogenesis. To understand the role of myopic ONH changes in glaucoma development, more extensive studies involving patients with myopic glaucoma are needed.…”

Section: Discussionmentioning

confidence: 99%

Longitudinal Observation of Border Tissue Configuration During Axial Elongation in Childhood

Kim

Choi

Girard

et al. 2021

Invest. Ophthalmol. Vis. Sci.

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Purpose To investigate the change of border tissue configuration during axial elongation in childhood. Methods Fifty-four subjects (108 eyes; age range, 29.3–132.5 months) who had undergone a series of swept-source optical coherence tomography scans at intervals of 6 months or longer were classified into stable axial length (AXL) eyes ( n = 55; AXL change of ≤0.36 mm) and elongating AXL eyes ( n = 53; AXL change of >0.36 mm). The angle between the Bruch's membrane opening (BMO) reference plane and the border tissue of Elschnig was defined as the border tissue angle (BTA). The border tissue angle, BMO distance (BMOD) and minimum rim width (MRW) were measured in the temporal and nasal regions. Results During 15.6 ± 7.2 months of follow-up, the AXL significantly increased from 22.8 ± 1.3 mm to 23.3 ± 1.4 mm ( P < 0.001). Changes of border tissue angle and AXL showed a significant correlation only in the temporal region of elongating AXL eyes ( r = –0.409; P = 0.002), but not in stable AXL eyes. Both BMOD and nasal MRW significantly increased from 1482.5 ± 153.0 to 1506.1 ± 154.6 µm and from 310.6 ± 83.2 to 324.6 ± 95.6 µm, respectively (all P s < 0.001). The changes of BMOD and nasal MRW showed a significant positive correlation with changes of AXL in elongating AXL eyes but not in stable AXL eyes. Conclusions During the axial elongation in childhood, temporal border tissue configuration change, BMO enlargement, and nasal peripapillary tissue elevation showed a significant correlation with changes in the AXL.

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Section: Discussionmentioning

confidence: 99%

Longitudinal Observation of Border Tissue Configuration During Axial Elongation in Childhood

Kim

Choi

Girard

et al. 2021

Invest. Ophthalmol. Vis. Sci.

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“… 20 , 21 These pressures were chosen because the normal pressure in control pig eyes is reported 15.2 ± 2.1 mm Hg 22 and the LC showed the greatest displacement at these pressures in our previous study. 20 , 21 , 23 With this setup, we imaged the microstructural organization and mechanical response of the LC using an excitation wavelength of 780 nm, collecting collagen (collection 377/50 nm) and elastin (collection 460/80 nm) simultaneously. Image datasets from sequential levels of pressure at 5 and 15 mm Hg were de-noised, processed to measure anterior-posterior displacement of the LC, and normalized to the displacement of the same eye before decellularization.…”

Section: Methodsmentioning

confidence: 99%

“…Three-dimensional (3D) images from an anterior viewpoint were taken using two-photon microscopy at 5 mm Hg and again at 15 mm Hg. 20,21 These pressures were chosen because the normal pressure in control pig eyes is reported 15.2 ± 2.1 mm Hg 22 and the LC showed the greatest displacement at these pressures in our previous study. 20,21,23 With this setup, we imaged the microstructural organization and mechanical response of the LC using an excitation wavelength of 780 nm, collecting collagen (collection 377/50 nm) and elastin (collection 460/80 nm) simultaneously.…”

Section: Pressurization and Lc Displacementmentioning

confidence: 99%

Decellularizing the Porcine Optic Nerve Head: Toward a Model to Study the Mechanobiology of Glaucoma

Liou

Drewry

Sweeney

et al. 2020

Trans. Vis. Sci. Tech.

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Studying the extracellular matrix (ECM) remodeling of the lamina cribrosa in vivo can be extremely challenging and costly. There exist very few options for studying optic nerve head (ONH) mechanobiology in vitro that are able to reproduce the complex anatomic and biomechanical environment of the ONH. Herein, we have developed a decellularization procedure that will enable more anatomically relevant and costefficient future studies of ECM remodeling of the ONH. Methods: Porcine posterior poles were decellularized using a detergent and enzymebased decellularization protocol. DNA quantification and histology were used to investigate the effectiveness of the protocol. We subsequently investigated the ability of a polyethylene glycol (PEG)-based hydrogel to restore the ONH's ability to hold pressure following decellularization. Anterior-posterior displacement of the decellularized and PEG treated ONH in a pressure bioreactor was used to evaluate the biomechanical response of the ONH. Results: DNA quantification and histology confirmed decellularization using Triton X-100 at low concentration for 48 hours successfully reduced the cellular content of the tissue by 94.9% compared with native tissue while preserving the ECM microstructure and basal lamina of the matrix. Infiltrating the decellularized tissues with PEG 6000 and PEG 10,000 hydrogel restored their ability to hold pressure, producing displacements similar to those measured for the non-decellularized control samples. Conclusions: Our decellularized ONH model is capable of producing scaffolds that are cell-free and maintain the native ECM microstructure. Translational Relevance: This model represents a platform to study the mechanobiology in the ONH and potentially for glaucoma drug testing.

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“…The S-DIC approach was used to track the position of speckles in each sweep at each pressure state. The 3D point cloud from each of the four sweeps for a given pressure were then combined to assemble the scleral and ONH geometry (Tamimi et al, 2017). The ONH was removed and the cross-sections of the points on the sclera at different segments were created in the sagittal view.…”

Section: Methodsmentioning

confidence: 99%

“…E was used to calculate first principal strains for each element. Additional details of the approach can be found in (Pyne et al, 2014; Tamimi et al, 2017). The intermediary pressure set measurements (15 and 30 mmHg) were utilized for the Finite element simulation and optimization.…”

Section: Methodsmentioning

confidence: 99%

A Subdomain Method for Mapping the Heterogeneous Mechanical Properties of the Human Posterior Sclera

Kollech

Ayyalasomayajula

Behkam

et al. 2019

Front. Bioeng. Biotechnol.

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Although strongly correlated with elevated intraocular pressure, primary open-angle glaucoma (POAG) occurs in normotensive eyes. Mechanical properties of the sclera around the optic nerve head (ONH) may play a role in this disparity. The purpose of this study is to present an automated inverse mechanics based approach to determine the distribution of heterogeneous mechanical properties of the human sclera as derived from its surface deformations arising from pressure inflation experiments. The scleral shell of a 78 year old European Descent male donor eye was utilized to demonstrate the method; the sclera was coated with a speckle pattern on the outer surface and was subjected to inflation pressures of 5, 15, 30, and 45 mmHg. The speckle pattern was imaged at each pressure, and a displacement field was calculated for each pressure step using a previously described sequential digital image correlation (S-DIC) technique. The fiber splay and fiber orientation of the sclera collagen were determined experimentally, and the thickness across the scleral globe was determined using micro CT images. The displacement field from the inflation test was used to calculate the strain and also used as an input for inverse mechanics to determine the heterogeneity of material properties. The scleral geometry was divided into subdomains using the first principal strain. The Holzapfel anisotropic material parameters of matrix and fiber stiffness were estimated within each individual subdomain using an inverse mechanics approach by minimizing the sum of the square of the residuals between the computational and experimental displacement fields. The mean and maximum error in displacement across all subdomains were 8.9 ± 3.0 μm and 13.2 μm, respectively. The full pressure-inflation forward mechanics experiment was done using subdomain-specific mechanical properties on the entire scleral surface. The proposed approach is effective in determining the distribution of heterogeneous mechanical properties of the human sclera in a user-independent manner. Our research group is currently utilizing this approach to better elucidate how scleral stiffness influences those at high risk for POAG.

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Racioethnic Differences in Human Posterior Scleral and Optic Nerve Stump Deformation

Cited by 11 publications

References 50 publications

Longitudinal Observation of Border Tissue Configuration During Axial Elongation in Childhood

Longitudinal Observation of Border Tissue Configuration During Axial Elongation in Childhood

Decellularizing the Porcine Optic Nerve Head: Toward a Model to Study the Mechanobiology of Glaucoma

A Subdomain Method for Mapping the Heterogeneous Mechanical Properties of the Human Posterior Sclera

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