Scleral structure and biomechanics

Boote, Craig; Sigal, Ian A.; Grytz, Rafael; Hua, Yi; Nguyen, Thao D.; Girard, M

doi:10.1016/j.preteyeres.2019.100773

Cited by 204 publications

(199 citation statements)

References 286 publications

(412 reference statements)

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“…Other techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were also used to increase our understanding of scleral architecture on the nanoscale level. 6 …”

Section: Introductionmentioning

confidence: 99%

“…There is a clear need for a micrometer-resolution technique, which can quickly and quantitatively assess scleral collagen fiber organization in vivo that can contribute to a better understanding of glaucoma and high myopia pathophysiology, and can aid in their diagnosis and management. 6 This technique should provide a high depth resolution to assess how the observed structural differences contribute to disease. 1 WAXS, SALS, and PLM are only available in 2D, and the only way to create 3D images is by slicing the tissue.…”

Section: Introductionmentioning

confidence: 99%

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In Vivo 3D Determination of Peripapillary Scleral and Retinal Layer Architecture Using Polarization-Sensitive Optical Coherence Tomography

Willemse

Gräfe

Verbraak

et al. 2020

Trans. Vis. Sci. Tech.

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Purpose The purpose of this paper was to determine the architecture of the collagen fibers of the peripapillary sclera, the retinal nerve fiber layer (RNFL), and Henle's fiber layer in vivo in 3D using polarization-sensitive optical coherence tomography (PS-OCT). Methods Seven healthy volunteers were imaged with our in-house built PS-OCT system. PS-OCT imaging included intensity, local phase retardation, relative optic axis, and optic axis uniformity (OAxU). Differential Mueller matrix calculus was used for the first time in ocular tissues to visualize local orientations that varied with depth, incorporating a correction method for the fiber orientation in preceding layers. Results Scleral collagen fiber orientation images clearly showed an inner layer with an orientation parallel to the RNFL orientation, and a deeper layer where the collagen was circularly oriented. RNFL orientation images visualized the nerve fibers leaving the optic nerve head (ONH) in a radial pattern. The phase retardation and orientation of Henle's fiber layer were visualized locally for the first time. Conclusions PS-OCT successfully showed the orientation of the retinal nerve fibers, sclera, and Henle's fiber layer, and is to the extent of our knowledge the only technique able to do so in 3D in vivo. Translational Relevance In vivo 3D imaging of scleral collagen architecture and the retinal neural fibrous structures can improve our understanding of retinal biomechanics and structural alterations in different disease stages of myopia and glaucoma.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In Vivo 3D Determination of Peripapillary Scleral and Retinal Layer Architecture Using Polarization-Sensitive Optical Coherence Tomography

Willemse

Gräfe

Verbraak

et al. 2020

Trans. Vis. Sci. Tech.

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“…Porcine and mouse samples were taken approximately 5mm and 0.5mm away from the optic nerve head, respectively. This location was chosen to avoid excessive circumferential alignment of collagen around the optic nerve head while remaining primarily in the posterior sclera [2]. Graphite powder was applied to scleral samples to reduce friction between samples and compression platens.…”

Section: Sample Preparationmentioning

confidence: 99%

“…Specifically, the sclera resists the stresses imposed on the eye wall by the intraocular pressure, making its structure and biomechanical properties critical to overall ocular shape and size [1]. Scleral biomechanics also directly impact the biomechanical loading imposed on the other more delicate tissues of the eye, including the retina and optic nerve head [2][3][4]. Pathological remodeling and altered material properties of the sclera have been implicated in a number of ocular pathologies, including myopia and glaucoma [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…A similar matrix has been found to impart complex triphasic biomechanics to articular cartilage by influencing hydration and ion distributions throughout the tissue [8], and it is likely to generally function in a similar capacity within the sclera. The proteoglycan-collagen matrix imbibes a large amount of fluid, making sclera ~70% water by weight [2]. Scleral fibroblasts actively maintain this proteoglycan and collagen matrix; however, a subset of these cells have also been shown to have contractile abilities, allowing them to interface with and actively influence biomechanics [9].…”

Section: Introductionmentioning

confidence: 99%

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A Biphasic Approach for Characterizing Tensile, Compressive, and Hydraulic Properties of the Sclera

Brown

Pardue

Ethier

2020

Preprint

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Measuring the biomechanical properties of the mouse sclera is of great interest, since altered scleral properties are features of many common ocular pathologies, and the mouse is a powerful species for studying genetic factors in disease. Here, a poroelastic material model is used to analyze data from unconfined compression testing of both pig and mouse sclera, and the tensile modulus, compressive modulus, and permeability of the sclera are obtained at three levels of compressive strain. Values for all three properties measured simultaneously by unconfined compression of pig sclera were comparable to previously reported values measured by tests specific for each property, i.e., compression tests, biaxial tensile tests, and falling-head permeability assays. The repeatability of the approach was evaluated using test-retest experimental paradigm on pig sclera. Repeatability was low for measured compressive stiffness, indicating permanent changes to the samples occurring after the first test. However, reasonable repeatability for tensile stiffness and permeability was observed. The intrinsic material properties of the mouse sclera were measured for the first time. Tensile stiffness and permeability of the sclera in both species were seen to be dependent on the state of compressive strain. We conclude that unconfined compression testing of sclera, when analyzed with poroelastic theory, can be used as a powerful tool to phenotype mouse scleral changes in future genotype-phenotype association studies. Statement of SignificanceOcular biomechanics is strongly influenced by the sclera, the outermost white coat of the eye. Many ocular diseases are believed to be influenced by pathological changes to scleral microstructure and biomechanics, making intrinsic biomechanical properties an important outcome measure in many studies. However, the small mouse eye precludes the use of most traditional biomechanical characterization techniques. Here, we show that unconfined compression testing analyzed with poroelastic theory can produce measurements of biomechanical properties in the pig sclera comparable to those measured by other traditional techniques. Importantly, this technique can be successfully applied to the mouse sclera, enabling more widespread use of the species as a model for ocular disease.

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Assessment of Ocular Deformation in Pathologic Myopia Using 3-Dimensional Magnetic Resonance Imaging

et al. 2023

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IMPORTANCEOcular deformation in pathologic myopia can affect the entire globe. However, few studies have investigated the equatorial pattern of ocular shape. In addition, the correlation between equatorial and posterior morphology needs to be further explored.OBJECTIVETo assess global ocular deformation in pathologic myopia.DESIGN, SETTING, AND PARTICIPANTSThis hospital-based, cross-sectional study included 180 pathologic myopic eyes with atrophic maculopathy grading C2 (diffuse chorioretinal atrophy) or more from 180 participants who underwent comprehensive ophthalmic examination, including high-resolution 3-dimensional magnetic resonance imaging. In addition, 10 nonpathologic myopic eyes of 10 participants were set as the control group.Main Outcomes and MeasuresAccording to the cross-sectional view of equator, equatorial shape was classified as round, rectangular, pyriform (noncircular and more protruded in 1 direction), vertical-elliptical, or horizontal-elliptical; according to the nasal and inferior views, the posterior shape was categorized as spheroidal, conical, bulb-shaped, ellipsoidal, multidistorted, and barrel-shaped. Equatorial circularity and ocular sphericity were used to quantitatively assess the morphological variability of the equatorial and posterior regions, respectively. The association between ocular morphology and ocular parameters and myopic maculopathy was also investigated.ResultsThe mean (SD) age of 180 participants with pathologic myopia was 55.14 (10.74) years, 127 were female (70.6%), and the mean (SD) axial length of studied eyes was 30.22 (2.25) mm. The predominant equatorial shape was pyriform (66 eyes [36.7%]), followed by round (45 eyes [25.0%]). The predominant posterior shape was bulb-shaped (97 eyes [52.2%]), followed by multidistorted (46 eyes [24.7%]). Equatorial circularity and equatorial shapes were correlated (r = −0.469; 95% CI, −0.584 to −0.346; P &lt; .001) and ocular sphericity was correlated with posterior shapes (r = −0.533; 95% CI, −0.627 to −0.427; P &lt; .001). In eyes with a vertical-elliptical equator, equatorial circularity and ocular sphericity were positively linearly correlated (R2 = 0.246; 95% CI, 0.050-0.496; P = .002) and the prevalence of inferior staphyloma was higher (27.8%; P = .04). Eyes with a horizontal-elliptical equator have the most horizontally oriented axis of corneal flat keratometry (median, 43.55 [interquartile range, 43.84] degrees; P = .01) and tended to present with multidistorted posterior shape (21.7%; P = .04).Conclusions and RelevanceThese findings suggest ocular deformation is common in pathologic myopia and can affect the entire eye, including the equatorial and posterior regions. The morphological classification may enhance the understanding of the diverse patterns of ocular shape in pathologic myopia.

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Scleral structure and biomechanics

Cited by 204 publications

References 286 publications

In Vivo 3D Determination of Peripapillary Scleral and Retinal Layer Architecture Using Polarization-Sensitive Optical Coherence Tomography

In Vivo 3D Determination of Peripapillary Scleral and Retinal Layer Architecture Using Polarization-Sensitive Optical Coherence Tomography

A Biphasic Approach for Characterizing Tensile, Compressive, and Hydraulic Properties of the Sclera

Assessment of Ocular Deformation in Pathologic Myopia Using 3-Dimensional Magnetic Resonance Imaging

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