Bioengineering

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16 pages, 5703 KiB

Open AccessArticle

Biomechanical Analysis and Clinical Study of Augmented Versus Conventional Endoscopic Orbital Decompression for Dysthyroid Optic Neuropathy

by Pengsen Wu, Yiheng Wu, Jing Rao, Shenglan Yang, Hongyi Yao, Qingjiang Liu, Yuqing Wu, Shengli Mi and Guiqin Liu

Bioengineering 2025, 12(6), 618; https://doi.org/10.3390/bioengineering12060618 - 5 Jun 2025

Viewed by 479

Abstract

Dysthyroid optic neuropathy (DON) represents a severe ocular complication in thyroid eye disease (TED) that can lead to vision loss. Although surgical decompression is a well-established treatment modality, the optimal decompression area remains controversial in orbital decompression surgery. Purpose: This study aims to [...] Read more.

Dysthyroid optic neuropathy (DON) represents a severe ocular complication in thyroid eye disease (TED) that can lead to vision loss. Although surgical decompression is a well-established treatment modality, the optimal decompression area remains controversial in orbital decompression surgery. Purpose: This study aims to develop and validate a finite element analysis (FEA) model of DON to compare the biomechanical behavior between patients undergoing conventional or augmented orbital decompression surgery, with potential clinical implications for surgical planning. Methods: FEA models were established using magnetic resonance imaging data from patients with myopathic TED. Pre-disease, preoperative, and postoperative FEA models were developed for both the conventional orbital decompression group and the augmented group, in which the posteromedial floor and the orbital process of the palatine bone were additionally removed to analyze the stress distribution and displacement of the optic nerve, eyeball, and orbital wall. A retrospective analysis was performed to validate the biomechanical analysis results. Results: The FEA results reveal that DON patients experience higher stress on the optic nerve, eyeball, and orbital wall than healthy individuals, mainly concentrated at the orbital apex. Postoperatively, the stress on the optic nerve was significantly reduced in both groups. In addition, postoperative stress on the optic nerve was significantly lower in the augmented group than in the conventional group. The clinical results demonstrate that patients in the augmented group experienced significantly faster and more pronounced improvements in visual acuity and visual field. Conclusions: FEA shows that augmented orbital decompression surgery can alleviate stress more effectively, especially for the optic nerve, which was validated by clinical analysis. This developed FEA model of DON may facilitate determining the appropriate surgical procedure for orbital decompression. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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17 pages, 9597 KiB

Open AccessArticle

Finite Element Model of the Effect of Optic Nerve Sheath Anisotropy on Ocular Loading During Horizontal Duction

by Somaye Jafari, Shengqiang Cai and Joseph L. Demer

Bioengineering 2025, 12(6), 587; https://doi.org/10.3390/bioengineering12060587 - 29 May 2025

Viewed by 529

Abstract

Previous models of extraocular mechanics have often assumed isotropic properties for ocular tissues, despite evidence indicating anisotropy in the optic nerve sheath (ONS). To investigate this further, we developed a finite element model (FEM) of horizontal eye rotation using MRI data from a [...] Read more.

Previous models of extraocular mechanics have often assumed isotropic properties for ocular tissues, despite evidence indicating anisotropy in the optic nerve sheath (ONS). To investigate this further, we developed a finite element model (FEM) of horizontal eye rotation using MRI data from a living subject with normal tension glaucoma. Mechanical properties were derived from tensile tests on 17 post-mortem human eyes, revealing previously unrecognized anisotropic characteristics in the ONS. We simulated ±32° horizontal eye rotations and compared isotropic versus anisotropic ONS properties using the Holzapfel model. Strain distributions in the optic nerve (ON) were analyzed using ABAQUS 2024 software. During 32° adduction, stress and strain were concentrated at the ONS-sclera junction, reaching 8 MPa and 40% with isotropic properties, and 15 MPa and 30% with anisotropic properties. In contrast, during 32° abduction, stress was lower and strain was higher in the isotropic case (6 MPa and 30%) compared to the anisotropic case (12 MPa and 25%). Increased intraocular and intracranial pressures had minimal impact on the mechanical responses. These findings suggest that the anisotropic properties of the ONS increase stress concentration at the optic disc while reducing strain during eye movements, offering new insights into ocular biomechanics. A novel phenomenon emerged from the simulations: during larger ductions, the peripapillary Bruch’s membrane is predicted to wrinkle, forming undulations with an approximately 20 μm amplitude and 100 μm wavelength at its interface with the retina and choroid. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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16 pages, 1719 KiB

Open AccessArticle

Finite Element Analysis of Ocular Impact Forces and Potential Complications in Pickleball-Related Eye Injuries

by Cezary Rydz, Jose A. Colmenarez, Kourosh Shahraki, Pengfei Dong, Linxia Gu and Donny W. Suh

Bioengineering 2025, 12(6), 570; https://doi.org/10.3390/bioengineering12060570 - 26 May 2025

Viewed by 476

Abstract

Purpose: Pickleball, the fastest-growing sport in the United States, has seen a rapid increase in participation across all age groups, particularly among older adults. However, the sport introduces specific risks for ocular injuries due to the unique dynamics of gameplay and the physical [...] Read more.

Purpose: Pickleball, the fastest-growing sport in the United States, has seen a rapid increase in participation across all age groups, particularly among older adults. However, the sport introduces specific risks for ocular injuries due to the unique dynamics of gameplay and the physical properties of the pickleball. This study aims to explore the mechanisms of pickleball-related eye injuries, utilizing finite element modeling (FEM) to simulate ocular trauma and better understand injury mechanisms. Methods: A multi-modal approach was employed to investigate pickleball-related ocular injuries. Finite element modeling (FEM) was used to simulate blunt trauma to the eye caused by a pickleball. The FEM incorporated detailed anatomical models of the periorbital structures, cornea, sclera, and vitreous body, using hyperelastic material properties derived from experimental data. The simulations evaluated various impact scenarios, including changes in ball velocity, angle of impact, and material stiffness, to determine the stress distribution, peak strain, and deformation in ocular structures. The FEM outputs were correlated with clinical findings to validate the injury mechanisms. Results: The FE analysis revealed that the rigid, hard-plastic construction of a pickleball results in concentrated stress and strain transfer to ocular structures upon impact. At velocities exceeding 30 mph, simulations showed significant corneal deformation, with peak stresses localized at the limbus and anterior sclera. Moreover, our results show a significant stress applied to lens zonules (as high as 0.35 MPa), leading to potential lens dislocation. Posterior segment deformation was also observed, with high strain levels in the retina and vitreous, consistent with clinical observations of retinal tears and vitreous hemorrhage. Validation against reported injuries confirmed the model’s accuracy in predicting both mild injuries (e.g., corneal abrasions) and severe outcomes (e.g., hyphema, globe rupture). Conclusions: Finite element analysis provides critical insights into the biomechanical mechanisms underlying pickleball-related ocular injuries. The findings underscore the need for preventive measures, particularly among older adults, who exhibit age-related vulnerabilities. Education on the importance of wearing protective eyewear and optimizing game rules to minimize high-risk scenarios, such as close-range volleys, is essential. Further refinement of the FEM, including parametric studies and integration of protective eyewear, can guide the development of safety standards and reduce the socio-economic burden of these injuries. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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11 pages, 1076 KiB

Open AccessArticle

Influence of Dextran Solution and Corneal Collagen Crosslinking on Corneal Biomechanical Parameters Evaluated by Corvis ST In Vitro

by Xiao Qin, Bi Hu, Lili Guo, Haixia Zhang, Lin Li, Ying Jie and Lei Tian

Bioengineering 2024, 11(11), 1156; https://doi.org/10.3390/bioengineering11111156 - 17 Nov 2024

Viewed by 1067

Abstract

Purpose: To analyze the influence of dextran solution and corneal collagen crosslinking (CXL) on corneal biomechanical parameters in vitro, evaluated by Corneal Visualization Scheimpflug Technology (Corvis ST). Materials and Methods: Forty porcine eyes were included in this study. Twenty porcine eyes were instilled [...] Read more.

Purpose: To analyze the influence of dextran solution and corneal collagen crosslinking (CXL) on corneal biomechanical parameters in vitro, evaluated by Corneal Visualization Scheimpflug Technology (Corvis ST). Materials and Methods: Forty porcine eyes were included in this study. Twenty porcine eyes were instilled with dextran solution for 30 min (10 eyes in 2% dextran solution and 10 eyes in 20% dextran solution). CXL treatment was performed in 10 porcine eyes; the other 10 porcine eyes were regarded as the control group. Each eye was fixed on an experimental inflation platform to carry out Corvis measurements at different IOPs. Corneal biomechanical parameters were calculated based on Corvis measurement. Statistical analysis was used to analyze the influence of dextran solution and CXL on corneal biomechanical parameters based on Corvis parameters. Results: The corneal energy-absorbed area (A_absorbed) decreased after being instilled with dextran solution under IOP of 15 mmHg (p < 0.001); the elastic modulus (E) of the cornea instilled with 20% dextran solution was significantly higher than that instilled with 2% dextran solution (p < 0.001), since it decreased after being instilled with 20% dextran solution (p = 0.030); the stiffness parameter at the first applanation (SP-A1) increased after CXL (p < 0.001). Conclusions: Both dextran solution and CXL can change corneal biomechanical properties; the concentration of dextran solution can influence the corneal biomechanical properties, which may, in turn, affect the effectiveness of CXL. SP-A1 may be used as an effective parameter for the evaluation of CXL. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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18 pages, 4984 KiB

Open AccessArticle

Effects of Genipin Crosslinking of Porcine Perilimbal Sclera on Mechanical Properties and Intraocular Pressure

by John Riesterer, Alexus Warchock, Erik Krawczyk, Linyu Ni, Wonsuk Kim, Sayoko E. Moroi, Guan Xu and Alan Argento

Bioengineering 2024, 11(10), 996; https://doi.org/10.3390/bioengineering11100996 - 2 Oct 2024

Viewed by 1517

Abstract

The mechanical properties of sclera play an important role in ocular functions, protection, and disease. Modulating the sclera’s properties by exogenous crosslinking offers a way to expand the tissue’s range of properties for study of the possible influences on the eye’s behavior and [...] Read more.

The mechanical properties of sclera play an important role in ocular functions, protection, and disease. Modulating the sclera’s properties by exogenous crosslinking offers a way to expand the tissue’s range of properties for study of the possible influences on the eye’s behavior and diseases such as glaucoma and myopia. The focus of this work was to evaluate the effects of genipin crosslinking targeting the porcine perilimbal sclera (PLS) since the stiffness of this tissue was previously found in a number of studies to influence the eye’s intraocular pressure (IOP). The work includes experiments on tensile test specimens and whole globes. The specimen tests showed decreased strain-rate dependence and increased relaxation stress due to the cross-linker. Whole globe perfusion experiments demonstrated that eyes treated with genipin in the perilimbal region had increased IOPs compared to the control globes. Migration of the cross-linker from the target tissue to other tissues is a confounding factor in whole globe, biomechanical measurements, with crosslinking. A novel quantitative genipin assay of the trabecular meshwork (TM) was developed to exclude globes where the TM was inadvertently crosslinked. The perfusion study, therefore, suggests that elevated stiffness of the PLS can significantly increase IOP apart from effects of the TM in the porcine eye. These results demonstrate the importance of PLS biomechanics in aqueous outflow regulation and support additional investigations into the distal outflow pathways as a key source of outflow resistance. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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28 pages, 42483 KiB

Open AccessArticle

Influence of Contact Lens Parameters on Cornea: Biomechanical Analysis

by Darshan Ramasubramanian, José Luis Hernández-Verdejo and José Manuel López-Alonso

Bioengineering 2024, 11(10), 966; https://doi.org/10.3390/bioengineering11100966 - 27 Sep 2024

Cited by 2 | Viewed by 2433

Abstract

This study presents a finite element analysis to model ocular biomechanics and the interactions between the human eye and contact lenses in the closed-eye condition. The closed-eye state, where the eyelids are fully shut, presents challenges for experimental measurements due to the invasive [...] Read more.

This study presents a finite element analysis to model ocular biomechanics and the interactions between the human eye and contact lenses in the closed-eye condition. The closed-eye state, where the eyelids are fully shut, presents challenges for experimental measurements due to the invasive nature of accessing and analysing the contact lens and corneal interface, making simulation tools valuable for accurate characterisation. The primary objective of this study was to examine how CLs fold and twist and their impact on the cornea when the eye is closed. The secondary aim of this study was to assess how crucial contact lens parameters (Young’s modulus, base curve, and diameter) influence corneal stress distribution and the overall fit of the lens on the eye. The findings show that increasing Young’s modulus significantly reduces corneal stress and promotes uniform stress distribution, making it the most influential factor for wearer comfort and safety. While base curve and diameter variations primarily affect contact area, their impact on stress distribution is minimal. This research provides insights for improving contact lens design and enhancing safety for contact lens wearers. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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20 pages, 4815 KiB

Open AccessArticle

Postmortem Digital Image Correlation and Finite Element Modeling Demonstrate Posterior Scleral Deformations during Optic Nerve Adduction Tethering

by Seongjin Lim, Changzoo Kim, Somaye Jafari, Joseph Park, Stephanie S. Garcia and Joseph L. Demer

Bioengineering 2024, 11(5), 452; https://doi.org/10.3390/bioengineering11050452 - 2 May 2024

Cited by 2 | Viewed by 2009

Abstract

Postmortem human eyes were subjected to optic nerve (ON) traction in adduction and elevated intraocular pressure (IOP) to investigate scleral surface deformations. We incrementally adducted 11 eyes (age 74.1 ± 9.3 years, standard deviation) from 26° to 32° under normal IOP, during imaging [...] Read more.

Postmortem human eyes were subjected to optic nerve (ON) traction in adduction and elevated intraocular pressure (IOP) to investigate scleral surface deformations. We incrementally adducted 11 eyes (age 74.1 ± 9.3 years, standard deviation) from 26° to 32° under normal IOP, during imaging of the posterior globe, for analysis by three-dimensional digital image correlation (3D-DIC). In the same eyes, we performed uniaxial tensile testing in multiple regions of the sclera, ON, and ON sheath. Based on individual measurements, we analyzed eye-specific finite element models (FEMs) simulating adduction and IOP loading. Analysis of 3D-DIC showed that the nasal sclera up to 1 mm from the sheath border was significantly compressed during adduction. IOP elevation from 15 to 30 mmHg induced strains less than did adduction. Tensile testing demonstrated ON sheath stiffening above 3.4% strain, which was incorporated in FEMs of adduction tethering that was quantitatively consistent with changes in scleral deformation from 3D-DIC. Simulated IOP elevation to 30 mmHg did not induce scleral surface strains outside the ON sheath. ON tethering in incremental adduction from 26° to 32° compressed the nasal and stretched the temporal sclera adjacent to the ON sheath, more so than IOP elevation. The effect of ON tethering is influenced by strain stiffening of the ON sheath. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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13 pages, 2004 KiB

Open AccessArticle

Optic Nerve Head Pulsatile Displacement in Open-Angle Glaucoma after Intraocular Pressure Reduction Measured by Optical Coherence Tomography: A Pilot Study

by Marissé Masís Solano, Emmanuelle Richer, Santiago Costantino and Mark R. Lesk

Bioengineering 2024, 11(5), 411; https://doi.org/10.3390/bioengineering11050411 - 23 Apr 2024

Cited by 1 | Viewed by 1519

Abstract

This study investigated the effect of intraocular pressure (IOP) reduction on pulsatile displacement within the optic nerve head (ONH) in primary open-angle glaucoma (POAG) patients with and without axial myopia. Forty-one POAG patients (19 without myopia, 9 with axial myopia and 13 glaucoma [...] Read more.

This study investigated the effect of intraocular pressure (IOP) reduction on pulsatile displacement within the optic nerve head (ONH) in primary open-angle glaucoma (POAG) patients with and without axial myopia. Forty-one POAG patients (19 without myopia, 9 with axial myopia and 13 glaucoma with no intervention) participated. Swept-source optical coherence tomography (OCT) videos of the ONH were obtained before and after IOP-lowering treatment (medical or surgical) achieving a minimum IOP drop of 3 mmHg. A demons registration-based algorithm measured local pulsatile displacement maps within the ONH. Results demonstrated a significant 14% decrease in pulsatile tissue displacement in the non-myopic glaucoma cohort after intervention (p = 0.03). However, glaucoma patients with axial myopia exhibited no statistically significant change. There were no significant changes in the pulsatile ONH deformation in the control group. These findings suggest a potential link between IOP reduction and reduced pulsatile displacement within the ONH in POAG patients without myopia, offering new insights into the disease’s pathophysiology and warranting further investigation into underlying mechanisms and clinical implications. Full article

(This article belongs to the Special Issue Biomechanics Studies in Ophthalmology)

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