Ocular biomechanics due to ground blast reinforcement

Karimi, Alireza; Razaghi, Reza; Girkin, Christopher A.; Downs, J. Crawford

doi:10.1016/j.cmpb.2021.106425

Cited by 13 publications

(5 citation statements)

References 70 publications

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“…Idealized µm-sized pores were distributed in the SC inner wall [ 74 ] with a pore density and diameter of 835 pores/mm 2 [ 30 ] and 1.3 µm [ 75 ], respectively ( Figure 1 a inset). Element quality assessment was conducted using Ansys (Ansys Inc., Pittsburgh, PA, USA) [ 52 , 73 , 76 , 77 , 78 ] to make sure the Jacobian ratio, aspect ratio, warping factor, and skewness were within the acceptable ranges for a good quality element (Ansys Inc.). Mesh density analyses were performed for the FE model described in our prior publications [ 53 , 60 ].…”

Section: Methodsmentioning

confidence: 99%

The Effect of Intraocular Pressure Load Boundary on the Biomechanics of the Human Conventional Aqueous Outflow Pathway

et al. 2022

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Background: Aqueous humor outflow resistance in the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and Schlemm’s canal (SC) endothelium of the conventional outflow pathway actively contribute to intraocular pressure (IOP) regulation. Outflow resistance is actively affected by the dynamic outflow pressure gradient across the TM, JCT, and SC inner wall tissues. The resistance effect implies the presence of a fluid–structure interaction (FSI) coupling between the outflow tissues and the aqueous humor. However, the biomechanical interactions between viscoelastic outflow tissues and aqueous humor dynamics are largely unknown. Methods: A 3D microstructural finite element (FE) model of a healthy human eye TM/JCT/SC complex was constructed with elastic and viscoelastic material properties for the bulk extracellular matrix and embedded elastic cable elements. The FE models were subjected to both idealized and a physiologic IOP load boundary using the FSI method. Results: The elastic material model for both the idealized and physiologic IOP load boundary at equal IOPs showed similar stresses and strains in the outflow tissues as well as pressure in the aqueous humor. However, outflow tissues with viscoelastic material properties were sensitive to the IOP load rate, resulting in different mechanical and hydrodynamic responses in the tissues and aqueous humor. Conclusions: Transient IOP fluctuations may cause a relatively large IOP difference of ~20 mmHg in a very short time frame of ~0.1 s, resulting in a rate stiffening in the outflow tissues. Rate stiffening reduces strains and causes a rate-dependent pressure gradient across the outflow tissues. Thus, the results suggest it is necessary to use a viscoelastic material model in outflow tissues that includes the important role of IOP load rate.

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Section: Methodsmentioning

confidence: 99%

The Effect of Intraocular Pressure Load Boundary on the Biomechanics of the Human Conventional Aqueous Outflow Pathway

et al. 2022

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“…The maximum IOP during an explosion can reach a peak of 0.29 MPa (2175 mmHg) at 1.63 ms, which is two times larger than the physiological IOP in healthy eyes [ 22 ]. Karimi et al [ 23 ] suggested that IOP could reach as high as 15,000–17,000 mmHg if ground blast reinforcement effects were considered in their three-dimensional (3D) finite element model of ocular blast injury. Blunt force crushing the eye can lead to contusion (a type of CGI) followed by rupture (a type of OGI) of the eyeball when its pressure limit is exceeded.…”

Section: Discussionmentioning

confidence: 99%

Explosive eye injuries: characteristics, traumatic mechanisms, and prognostic factors for poor visual outcomes

Zhang

Kang

et al. 2023

Military Med Res

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Background Explosions can produce blast waves, high-speed medium, thermal radiation, and chemical spatter, leading to complex and compound eye injuries. However, few studies have comprehensively investigated the clinical features of different eye injury types or possible risk factors for poor prognosis. Methods We retrospectively reviewed all consecutive records of explosive eye injuries (1449 eyes in 1115 inpatients) in 14 tertiary referral hospitals in China over 12 years (between January 2008 and December 2019). Data on demographics, eye injury types, ocular findings, treatments, and factors affecting visual prognosis were extracted from a standardized database of eye injuries and statistically analyzed. Results Mechanical ocular trauma accounted for 94.00% of explosion-related eye injuries, among which intraocular foreign bodies (IOFBs) resulted in 55.17% of open globe injuries (OGIs) and contusion caused 60.22% of close globe injuries (CGIs). Proliferative vitreous retinopathy (PVR) was more common in perforating (47.06%) and IOFB (26.84%) than in penetrating (8.79%) injuries, and more common with laceration (24.25%) than rupture (9.22%, P < 0.01). However, no difference was observed between rupture and contusion. Ultimately, 9.59% of eyes were removed and the final vision was ≤ 4/200 in 45.82% of patients. Poor presenting vision [odds ratio (OR) = 5.789], full-thickness laceration of the eyeball ≥ 5 mm (OR = 3.665), vitreous hemorrhage (OR = 3.474), IOFB (OR = 3.510), non-mechanical eye injury (NMEI, OR = 2.622, P < 0.001), rupture (OR = 2.362), traumatic optic neuropathy (OR = 2.102), retinal detachment (RD, OR = 2.033), endophthalmitis (OR = 3.281, P < 0.01), contusion (OR = 1.679), ciliary body detachment (OR = 6.592), zone III OGI (OR = 1.940), and PVR (OR = 1.615, P < 0.05) were significant negative predictors for poor visual outcomes. Conclusions Explosion ocular trauma has complex mechanisms, with multiple eyes involved and poor prognosis. In lethal level I explosion injuries, eyeball rupture is a serious condition, whereas contusion is more likely to improve. In level II injuries, IOFBs are more harmful than penetrating injuries, and level IV represents burn-related eye injuries. PVR is more associated with penetrating mechanisms than with OGI. Identifying the risk predictors for visual prognosis can guide clinicians in the evaluation and treatment of ocular blast injuries.

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“…The models were meshed with 8-noded hexahedral elements [ 59 ], including 348,861 elements and 433,636 nodes, and the element edge length of ~0.5–1 μm. Element quality assessment and time-step analysis were carried out using LS-DYNA (Ansys/LS-DYNA, Pennsylvania, US) [ 48 , 54 , 60 , 61 , 62 ]. Mesh density analyses were conducted for the FE model as described in our previous publications [ 46 , 47 , 49 , 50 ].…”

Section: Methodsmentioning

confidence: 99%

Modeling the Endothelial Glycocalyx Layer in the Human Conventional Aqueous Outflow Pathway

Karimi

Halabian

Razaghi

et al. 2022

Cells

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A layer of proteoglycans and glycoproteins known as glycocalyx covers the surface of the trabecular meshwork (TM), juxtacanalicular tissue (JCT), and Schlemm’s canal (SC) inner wall of the conventional aqueous outflow pathway in the eye. This has been shown to play a role in the mechanotransduction of fluid shear stress and in the regulation of the outflow resistance. The outflow resistance in the conventional outflow pathway is the main determinant of the intraocular pressure (IOP) through an active, two-way, fluid–structure interaction coupling between the outflow tissues and aqueous humor. A 3D microstructural finite element (FE) model of a healthy human eye TM/JCT/SC complex with interspersed aqueous humor was constructed. A very thin charged double layer that represents the endothelial glycocalyx layer covered the surface of the elastic outflow tissues. The aqueous humor was modeled as electroosmotic flow that is charged when it is in contact with the outflow tissues. The electrical–fluid–structure interaction (EFSI) method was used to couple the charged double layer (glycocalyx), fluid (aqueous humor), and solid (outflow tissues). When the IOP was elevated to 15 mmHg, the maximum aqueous humor velocity in the EFSI model was decreased by 2.35 mm/s (9%) compared to the fluid–structure interaction (FSI) model. The charge or electricity in the living human conventional outflow pathway generated by the charged endothelial glycocalyx layer plays a minor biomechanical role in the resultant stresses and strains as well as the hydrodynamics of the aqueous humor.

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Ocular biomechanics due to ground blast reinforcement

Cited by 13 publications

References 70 publications

The Effect of Intraocular Pressure Load Boundary on the Biomechanics of the Human Conventional Aqueous Outflow Pathway

The Effect of Intraocular Pressure Load Boundary on the Biomechanics of the Human Conventional Aqueous Outflow Pathway

Explosive eye injuries: characteristics, traumatic mechanisms, and prognostic factors for poor visual outcomes

Modeling the Endothelial Glycocalyx Layer in the Human Conventional Aqueous Outflow Pathway

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