GLORIA

GEOMAR Library Ocean Research Information Access

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Material
Language
  • 1
    In: Journal of Biomechanical Engineering, ASME International, Vol. 131, No. 5 ( 2009-05-01)
    Abstract: The posterior sclera likely plays an important role in the development of glaucoma, and accurate characterization of its mechanical properties is needed to understand its impact on the more delicate optic nerve head—the primary site of damage in the disease. The posterior scleral shells from both eyes of one rhesus monkey were individually mounted on a custom-built pressurization apparatus. Intraocular pressure was incrementally increased from 5 mm Hg to 45 mm Hg, and the 3D displacements were measured using electronic speckle pattern interferometry. Finite element meshes of each posterior scleral shell were reconstructed from data generated by a 3D digitizer arm (shape) and a 20 MHz ultrasound transducer (thickness). An anisotropic hyperelastic constitutive model described in a companion paper (Girard, Downs, Burgoyne, and Suh, 2009, “Peripapillary and Posterior Scleral Mechanics—Part I: Development of an Anisotropic Hyperelastic Constitutive Model,” ASME J. Biomech. Eng., 131, p. 051011), which includes stretch-induced stiffening and multidirectional alignment of the collagen fibers, was applied to each reconstructed mesh. Surface node displacements of each model were fitted to the experimental displacements using an inverse finite element method, which estimated a unique set of 13 model parameters. The predictions of the proposed constitutive model matched the 3D experimental displacements well. In both eyes, the tangent modulus increased dramatically with IOP, which indicates that the sclera is mechanically nonlinear. The sclera adjacent to the optic nerve head, known as the peripapillary sclera, was thickest and exhibited the lowest tangent modulus, which might have contributed to the uniform distribution of the structural stiffness for each entire scleral shell. Posterior scleral deformation following acute IOP elevations appears to be nonlinear and governed by the underlying scleral collagen microstructure as predicted by finite element modeling. The method is currently being used to characterize posterior scleral mechanics in normal (young and old), early, and moderately glaucomatous monkey eyes.
    Type of Medium: Online Resource
    ISSN: 0148-0731 , 1528-8951
    Language: English
    Publisher: ASME International
    Publication Date: 2009
    SSG: 31
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Online Resource
    Online Resource
    Association for Research in Vision and Ophthalmology (ARVO) ; 2015
    In:  Investigative Opthalmology & Visual Science Vol. 56, No. 3 ( 2015-03-31), p. 1872-
    In: Investigative Opthalmology & Visual Science, Association for Research in Vision and Ophthalmology (ARVO), Vol. 56, No. 3 ( 2015-03-31), p. 1872-
    Type of Medium: Online Resource
    ISSN: 1552-5783
    Language: English
    Publisher: Association for Research in Vision and Ophthalmology (ARVO)
    Publication Date: 2015
    detail.hit.zdb_id: 2009858-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    Online Resource
    Online Resource
    Association for Research in Vision and Ophthalmology (ARVO) ; 2011
    In:  Investigative Opthalmology & Visual Science Vol. 52, No. 8 ( 2011-07-28), p. 5656-
    In: Investigative Opthalmology & Visual Science, Association for Research in Vision and Ophthalmology (ARVO), Vol. 52, No. 8 ( 2011-07-28), p. 5656-
    Type of Medium: Online Resource
    ISSN: 1552-5783
    Language: English
    Publisher: Association for Research in Vision and Ophthalmology (ARVO)
    Publication Date: 2011
    detail.hit.zdb_id: 2009858-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 4
    Online Resource
    Online Resource
    Association for Research in Vision and Ophthalmology (ARVO) ; 2009
    In:  Investigative Opthalmology & Visual Science Vol. 50, No. 11 ( 2009-11-01), p. 5226-
    In: Investigative Opthalmology & Visual Science, Association for Research in Vision and Ophthalmology (ARVO), Vol. 50, No. 11 ( 2009-11-01), p. 5226-
    Type of Medium: Online Resource
    ISSN: 1552-5783
    Language: English
    Publisher: Association for Research in Vision and Ophthalmology (ARVO)
    Publication Date: 2009
    detail.hit.zdb_id: 2009858-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 5
    In: Current Eye Research, Informa UK Limited, Vol. 40, No. 1 ( 2015-01-02), p. 1-18
    Type of Medium: Online Resource
    ISSN: 0271-3683 , 1460-2202
    RVK:
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2015
    detail.hit.zdb_id: 1483048-6
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 6
    Online Resource
    Online Resource
    Association for Research in Vision and Ophthalmology (ARVO) ; 2012
    In:  Investigative Opthalmology & Visual Science Vol. 53, No. 9 ( 2012-08-09), p. 5326-
    In: Investigative Opthalmology & Visual Science, Association for Research in Vision and Ophthalmology (ARVO), Vol. 53, No. 9 ( 2012-08-09), p. 5326-
    Type of Medium: Online Resource
    ISSN: 1552-5783
    Language: English
    Publisher: Association for Research in Vision and Ophthalmology (ARVO)
    Publication Date: 2012
    detail.hit.zdb_id: 2009858-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 7
    Online Resource
    Online Resource
    Association for Research in Vision and Ophthalmology (ARVO) ; 2019
    In:  Investigative Opthalmology & Visual Science Vol. 60, No. 13 ( 2019-10-09), p. 4141-
    In: Investigative Opthalmology & Visual Science, Association for Research in Vision and Ophthalmology (ARVO), Vol. 60, No. 13 ( 2019-10-09), p. 4141-
    Type of Medium: Online Resource
    ISSN: 1552-5783
    Language: English
    Publisher: Association for Research in Vision and Ophthalmology (ARVO)
    Publication Date: 2019
    detail.hit.zdb_id: 2009858-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 8
    In: JAMA Ophthalmology, American Medical Association (AMA), Vol. 141, No. 9 ( 2023-09-01), p. 882-
    Abstract: The 3-dimensional (3-D) structural phenotype of glaucoma as a function of severity was thoroughly described and analyzed, enhancing understanding of its intricate pathology beyond current clinical knowledge. Objective To describe the 3-D structural differences in both connective and neural tissues of the optic nerve head (ONH) between different glaucoma stages using traditional and artificial intelligence–driven approaches. Design, Setting, and Participants This cross-sectional, clinic-based study recruited 541 Chinese individuals receiving standard clinical care at Singapore National Eye Centre, Singapore, and 112 White participants of a prospective observational study at Vilnius University Hospital Santaros Klinikos, Vilnius, Lithuania. The study was conducted from May 2022 to January 2023. All participants had their ONH imaged using spectral-domain optical coherence tomography and had their visual field assessed by standard automated perimetry. Main Outcomes and Measures (1) Clinician-defined 3-D structural parameters of the ONH and (2) 3-D structural landmarks identified by geometric deep learning that differentiated ONHs among 4 groups: no glaucoma, mild glaucoma (mean deviation [MD], ≥−6.00 dB), moderate glaucoma (MD, −6.01 to −12.00 dB), and advanced glaucoma (MD, & amp;lt;−12.00 dB). Results Study participants included 213 individuals without glaucoma (mean age, 63.4 years; 95% CI, 62.5-64.3 years; 126 females [59.2%]; 213 Chinese [100%] and 0 White individuals), 204 with mild glaucoma (mean age, 66.9 years; 95% CI, 66.0-67.8 years; 91 females [44.6%]; 178 Chinese [87.3%] and 26 White [12.7%] individuals), 118 with moderate glaucoma (mean age, 68.1 years; 95% CI, 66.8-69.4 years; 49 females [41.5%] ; 97 Chinese [82.2%] and 21 White [17.8%] individuals), and 118 with advanced glaucoma (mean age, 68.5 years; 95% CI, 67.1-69.9 years; 43 females [36.4%]; 53 Chinese [44.9%] and 65 White [55.1%] individuals). The majority of ONH structural differences occurred in the early glaucoma stage, followed by a plateau effect in the later stages. Using a deep neural network, 3-D ONH structural differences were found to be present in both neural and connective tissues. Specifically, a mean of 57.4% (95% CI, 54.9%-59.9%, for no to mild glaucoma), 38.7% (95% CI, 36.9%-40.5%, for mild to moderate glaucoma), and 53.1 (95% CI, 50.8%-55.4%, for moderate to advanced glaucoma) of ONH landmarks that showed major structural differences were located in neural tissues with the remaining located in connective tissues. Conclusions and Relevance This study uncovered complex 3-D structural differences of the ONH in both neural and connective tissues as a function of glaucoma severity. Future longitudinal studies should seek to establish a connection between specific 3-D ONH structural changes and fast visual field deterioration and aim to improve the early detection of patients with rapid visual field loss in routine clinical care.
    Type of Medium: Online Resource
    ISSN: 2168-6165
    Language: English
    Publisher: American Medical Association (AMA)
    Publication Date: 2023
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 9
    Online Resource
    Online Resource
    ASME International ; 2008
    In:  Journal of Biomechanical Engineering Vol. 130, No. 4 ( 2008-08-01)
    In: Journal of Biomechanical Engineering, ASME International, Vol. 130, No. 4 ( 2008-08-01)
    Abstract: To experimentally characterize 2D surface mapping of the deformation pattern of porcine peripapillary sclera following acute elevations of intraocular pressure (IOP) from 5mmHgto45mmHg. Four porcine eyes were obtained within 48h postmortem and dissected to the sclera. After the anterior chamber was removed, each posterior scleral shell was individually mounted at the equator on a custom-built pressurization device, which internally pressurized the scleral samples with isotonic saline at 22°C. Black polystyrene microspheres (10μm in diameter) were randomly scattered and attached to the scleral surface. IOP was incrementally increased from 5mmHgto45mmHg(±0.15mmHg), and the surface deformation of the peripapillary sclera immediately adjacent to the dural insertion was optically tracked at a resolution of 2μm∕pixel one quadrant at a time, for each of four quadrants (superior, nasal, inferior, and temporal). The 2D displacement data of the microsphere markers were extracted using the optical flow equation, smoothed by weighting function interpolation, and converted to the corresponding Lagrangian finite surface strain. In all four quadrants of each eye, the principal strain was highest and primarily circumferential immediately adjacent to the scleral canal. Average maximum Lagrangian strain across all quadrants for all eyes was 0.013±0.005 from 5mmHgto10mmHg, 0.014±0.004 from 10mmHgto30mmHg and 0.004±0.001 from 30mmHgto45mmHg, demonstrating the nonlinearity in the IOP-strain relationship. For each scleral shell, the observed surface strain mapping implied that the scleral stiffness was relatively low between 5mmHg and 10mmHg, but dramatically increased for each IOP elevation increment beyond 10mmHg. Peripapillary deformation following an acute IOP elevation may be governed by the underlying scleral collagen microstructure and is likely in the high-stiffness region of the scleral stress-strain curve when IOP is above 10mmHg.
    Type of Medium: Online Resource
    ISSN: 0148-0731 , 1528-8951
    Language: English
    Publisher: ASME International
    Publication Date: 2008
    SSG: 31
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 10
    Online Resource
    Online Resource
    ASME International ; 2009
    In:  Journal of Biomechanical Engineering Vol. 131, No. 5 ( 2009-05-01)
    In: Journal of Biomechanical Engineering, ASME International, Vol. 131, No. 5 ( 2009-05-01)
    Abstract: The sclera is the white outer shell and principal load-bearing tissue of the eye as it sustains the intraocular pressure. We have hypothesized that the mechanical properties of the posterior sclera play a significant role in and are altered by the development of glaucoma—an ocular disease manifested by structural damage to the optic nerve head. An anisotropic hyperelastic constitutive model is presented to simulate the mechanical behavior of the posterior sclera under acute elevations of intraocular pressure. The constitutive model is derived from fiber-reinforced composite theory, and incorporates stretch-induced stiffening of the reinforcing collagen fibers. Collagen fiber alignment was assumed to be multidirectional at local material points, confined within the plane tangent to the scleral surface, and described by the semicircular von Mises distribution. The introduction of a model parameter, namely, the fiber concentration factor, was used to control collagen fiber alignment along a preferred fiber orientation. To investigate the effects of scleral collagen fiber alignment on the overall behaviors of the posterior sclera and optic nerve head, finite element simulations of an idealized eye were performed. The four output quantities analyzed were the scleral canal expansion, the scleral canal twist, the posterior scleral canal deformation, and the posterior laminar deformation. A circumferential fiber organization in the sclera restrained scleral canal expansion but created posterior laminar deformation, whereas the opposite was observed with a meridional fiber organization. Additionally, the fiber concentration factor acted as an amplifying parameter on the considered outputs. The present model simulation suggests that the posterior sclera has a large impact on the overall behavior of the optic nerve head. It is therefore primordial to provide accurate mechanical properties for this tissue. In a companion paper (Girard, Downs, Bottlang, Burgoyne, and Suh, 2009, “Peripapillary and Posterior Scleral Mechanics—Part II: Experimental and Inverse Finite Element Characterization,” ASME J. Biomech. Eng., 131, p. 051012), we present a method to measure the 3D deformations of monkey posterior sclera and extract mechanical properties based on the proposed constitutive model with an inverse finite element method.
    Type of Medium: Online Resource
    ISSN: 0148-0731 , 1528-8951
    Language: English
    Publisher: ASME International
    Publication Date: 2009
    SSG: 31
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...