Biomechanical properties of retina and choroid: a comprehensive review of techniques and translational relevance

Ferrara, Mariantonia; Lugano, Gaia; Sandinha, Teresa; Kearns, Victoria; Geraghty, Brendan; Steel, David

doi:10.1038/s41433-021-01437-w

Cited by 41 publications

(34 citation statements)

References 95 publications

(216 reference statements)

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“…The choroid is a vascular layer situated between the sclera and the retina. It is composed of several layers: the choriocapillaris, 10 µm-thick capillary network; the Sattler’s layer, composed of arterioles, small arteries, and veins; Haller’s layer, composed of larger blood vessels; the suprachoroid, which is non-vascular, composed of melanocytes, fibroblasts and collagen; and the lamina fusca, separating the choroid from the sclera [ 22 ]. It is a highly vascularized space, as the flow per perfused volume is the highest of any other human tissue [ 23 ].…”

Section: Discussionmentioning

confidence: 99%

Effect of SCUBA Diving on Ophthalmic Parameters

et al. 2022

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Background and Objective: Several cases of central serous chorioretinopathy (CSC) in divers have been reported in our medical retina center over the past few years. This study was designed to evaluate possible changes induced by SCUBA diving in ophthalmic parameters and especially subfoveal choroidal thickness (SFCT), since the choroid seems to play a crucial role in physiopathology of CSC. Materials and Methods: Intraocular pressure (IOP), SFCT, pachymetry, flow-mediated dilation (FMD), blood pressure, and heart rate were measured in 15 healthy volunteer divers before diving, 30 and 60 min after a standard deep dive of 25 m depth for 25 min in a dedicated diving pool (NEMO 33). Results: SFCT reduces significantly to 96.63 ± 13.89% of pre-dive values (p = 0.016) 30 min after diving. It recovers after 60 min reaching control values. IOP decreases to 88.05 ± 10.04% of pre-dive value at 30 min, then increases to 91.42 ± 10.35% of its pre-dive value (both p < 0.0001). Pachymetry shows a slight variation, but is significantly increased to 101.63 ± 1.01% (p = 0.0159) of the pre-dive value, and returns to control level after 60 min. FMD pre-dive was 107 ± 6.7% (p < 0.0001), but post-dive showed a diminished increase to 103 ± 6.5% (p = 0.0132). The pre-post difference was significant (p = 0.03). Conclusion: Endothelial dysfunction leading to arterial stiffness after diving may explain the reduced SFCT observed, but SCUBA diving seems to have miscellaneous consequences on eye parameters. Despite this clear influence on SFCT, no clear relationship between CSC and SCUBA diving can be drawn.

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Section: Discussionmentioning

confidence: 99%

Effect of SCUBA Diving on Ophthalmic Parameters

et al. 2022

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“…[194] By contrast, under tension, the retina had mechanical properties between 13 and 19 kPa. [195] The retina exhibits a tan(δ) ≈ 0.4, [196] while the sclera has tan(δ) ≈ 0.15, with a half-time for stress relaxation ≈82 s. [197]…”

Section: Properties Of the Cnsmentioning

confidence: 99%

Materials for Implantable Surface Electrode Arrays: Current Status and Future Directions

Tringides

Mooney

2022

Advanced Materials

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with the outermost layer of biological tissues, often spanning a significant surface area. Devices typically have multiple electrodes that aim to monitor and modulate cells and tissues in a minimally invasive manner, using biomaterials designed to evoke minimal inflammatory responses. Applications of Surface Electrode Arrays RecordingBecause surface electrode arrays can record a "snapshot" of the electrical activity at distinct locations, these arrays are useful to monitor the function of a tissue. Though the recordings are typically local field potentials, with electrodes that are small enough to modulate as little of a location as possible while still maintaining a sufficiently high conductivity, single units from individual cells have been reported. Clinically, these recordings are used to map the epicardial surface to identify instances, and potentially mechanisms, of chronic atrial fibrillation, [1] dysfunction of ventricular tachycardia caused by congenital defects, [2] and other abnormal conduction conditions in the cardiac system. Clinical electrocorticogram (ECoG) is used to identify similar functional changes on the cortical surface of the brain, most commonly to identify epileptic focal center(s), or detect seizure activity. [3][4][5][6][7] Other functional uses of ECoG include intraoperative monitoring during tumor resection. [8] A surgeon can ask a patient to perform an activity such as a speech and then identify and avoid the active cortical regions during surgery, to avoid major disruptions to the patient quality of life. StimulationInstead of passively monitoring electrical activity, multielectrode surface arrays can provide electrical current to the underlying tissue and induce a desired excitatory or inhibitory response. The applications for stimulating surface electrode arrays are often therapeutic and include implantable pacemakers, which restore a normal cardiac rhythm by providing external and overriding cues to the cardiomyocytes responsible for establishing a sinus rhythm. [9] Pulses delivered to specific regions of the spinal cord are used to manage chronic pain, [10][11][12] and more recently as a therapy to promote neuronal plasticity in Surface electrode arrays are mainly fabricated from rigid or elastic materials, and precisely manipulated ductile metal films, which offer limited stretchability. However, the living tissues to which they are applied are nonlinear viscoelastic materials, which can undergo significant mechanical deformation in dynamic biological environments. Further, the same arrays and compositions are often repurposed for vastly different tissues rather than optimizing the materials and mechanical properties of the implant for the target application. By first characterizing the desired biological environment, and then designing a technology for a particular organ, surface electrode arrays may be more conformable, and offer better interfaces to tissues while causing less damage. Here, the various materials used in each component of a surface electrode array are first r...

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“…Therefore, it is vital that the biomechanical properties and computational models of the eye soft tissues are developed with the view to understand the mechanisms of various diseases of the eye. Biomechanical properties of eye soft tissues are vital in improving insight into how eye diseases progress [11].…”

Section: Introductionmentioning

confidence: 99%

Biaxial Estimation of Biomechanical Constitutive Parameters of Passive Porcine Sclera Soft Tissue

Ndlovu

Desai

Pandelani

et al. 2022

Applied Bionics and Biomechanics

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This study assesses the modelling capabilities of four constitutive hyperelastic material models to fit the experimental data of the porcine sclera soft tissue. It further estimates the material parameters and discusses their applicability to a finite element model by examining the statistical dispersion measured through the standard deviation. Fifteen sclera tissues were harvested from porcine’ slaughtered at an abattoir and were subjected to equi-biaxial testing. The results show that all the four material models yielded very good correlations at correlations above 96%. The polynomial (anisotropic) model gave the best correlation of 98%. However, the estimated material parameters varied widely from one test to another such that there would be need to normalise the test data to avoid long optimisation processes after applying the average material parameters to finite element models. However, for application of the estimated material parameters to finite element models, there would be need to consider normalising the test data to reduce the search region for the optimisation algorithms. Although the polynomial (anisotropic) model yielded the best correlation, it was found that the Choi-Vito had the least variation in the estimated material parameters, thereby making it an easier option for application of its material parameters to a finite element model and requiring minimum effort in the optimisation procedure. For the porcine sclera tissue, it was found that the anisotropy was more influenced by the fiber-related properties than the background material matrix-related properties.

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Biomechanical properties of retina and choroid: a comprehensive review of techniques and translational relevance

Cited by 41 publications

References 95 publications

Effect of SCUBA Diving on Ophthalmic Parameters

Effect of SCUBA Diving on Ophthalmic Parameters

Materials for Implantable Surface Electrode Arrays: Current Status and Future Directions

Biaxial Estimation of Biomechanical Constitutive Parameters of Passive Porcine Sclera Soft Tissue

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