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Villegas L, Zvietcovich F, Marcos S, Birkenfeld JS. Revealing regional variations in scleral shear modulus in a rabbit eye model using multi-directional ultrasound optical coherence elastography. Sci Rep 2024; 14:21010. [PMID: 39251655 DOI: 10.1038/s41598-024-71343-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2024] [Accepted: 08/27/2024] [Indexed: 09/11/2024] Open
Abstract
The mechanical properties of the sclera play a critical role in supporting the ocular structure and maintaining its shape. However, non-invasive measurements to quantify scleral biomechanics remain challenging. Recently introduced multi-directional optical coherence elastography (OCE) combined with an air-coupled ultrasound transducer for excitation of elastic surface waves was used to estimate phase speed and shear modulus in ex vivo rabbit globes (n = 7). The scleral phase speed (12.1 ± 3.2 m/s) was directional-dependent and higher than for corneal tissue (5.9 ± 1.4 m/s). In the tested locations, the sclera proved to be more anisotropic than the cornea by a factor of 11 in the maximum of modified planar anisotropy coefficient. The scleral shear moduli, estimated using a modified Rayleigh-Lamb wave model, showed significantly higher values in the circumferential direction (65.4 ± 31.9 kPa) than in meridional (22.5 ± 7.2 kPa); and in the anterior zone (27.3 ± 9.3 kPa) than in the posterior zone (17.8 ± 7.4 kPa). The multi-directional scanning approach allowed both quantification and radial mapping of estimated parameters within a single measurement. The results indicate that multi-directional OCE provides a valuable non-invasive assessment of scleral tissue properties that may be useful in the development of improved ocular models, the evaluation of potential myopia treatment strategies, and disease characterization and monitoring.
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Affiliation(s)
- Lupe Villegas
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
| | - Fernando Zvietcovich
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Department of Engineering, Pontificia Universidad Católica del Peru, Lima, Peru
| | - Susana Marcos
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- The Center for Visual Science, The Institute of Optics, Flaum Eye Institute, University of Rochester, Rochester, NY, USA
| | - Judith S Birkenfeld
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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Sun Y, Guo Y, Pang R, Peng J, Cao K, Wang N. Corneal biomechanical properties and potential influencing factors in varying degrees of myopia. Sci Rep 2024; 14:20626. [PMID: 39232107 PMCID: PMC11374800 DOI: 10.1038/s41598-024-71676-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2024] [Accepted: 08/29/2024] [Indexed: 09/06/2024] Open
Abstract
To compare the corneal biomechanical parameters measured by Corvis ST in subjects with varying degrees of myopia. And the factors that may affect corneal biomechanical properties were also investigated. Participants in this prospective cross-sectional study were classified into three groups according to spherical equivalent (SE) and axial length (AL): Non-myopia (NM, SE > - 0.50 D and AL < 26 mm), Mild-to-moderate myopia (MM, - 6.00 D < SE ≤ - 0.50 D and AL < 26 mm), high myopia (HM, SE ≤ - 6.00 D or AL ≥ 26 mm). Ten corneal biomechanical parameters were finally included. Linear mixed-effects model accounting for using both eyes in the same participant was carried out to evaluate how the corneal biomechanical parameter was influenced by varying degrees of myopia after adjusting for biomechanically corrected intraocular pressure (bIOP) and central corneal thickness (CCT). Further, multiple linear regression was performed to explore the correlation between corneal biomechanical parameter and SE, AL, bIOP or CCT. A total of 304 eyes from 224 healthy myopic subjects were recorded. There were 95 eyes with NM, 122 eyes with MM, and 87 eyes with HM. After adjusting for bIOP and CCT, eyes with high myopia showed shorter highest concavity time (HC-time, p = 0.025), greater peak distance (PD, p = 0.001), greater deflection amplitude (DA-Max, p = 0.002), smaller whole eye movement (WEM-Max, p < 0.001) and reduced stiffness parameter (SP-A1, p < 0.001). Multiple regression analysis showed that five parameters (HC-time, p < 0.001; PD, p < 0.001; DA-Max, p = 0.001; WEM-Max, p < 0.001; and SP-A1, p < 0.001) of Corvis ST were significantly correlated with AL, and one parameter (Corvis biomechanical index, p = 0.016) has significant relationship with SE. With the increase of myopia, significant changes in several corneal biomechanical parameters indicated a progressive decrease in corneal stiffness, independent of bIOP and CCT. Corneal biomechanical parameters may be predictors of scleral mechanical strength in high myopia, which has certain application value in clinical management of myopia.
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Affiliation(s)
- Yunxiao Sun
- Beijing Ophthalmology and Visual Sciences Key Lab, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, No. 1 Dongjiaominxiang Street, Dongcheng District, Beijing, 100730, China
| | - Yiqin Guo
- Beijing Ophthalmology and Visual Sciences Key Lab, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, No. 1 Dongjiaominxiang Street, Dongcheng District, Beijing, 100730, China
| | - Ruiqi Pang
- Beijing Ophthalmology and Visual Sciences Key Lab, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, No. 1 Dongjiaominxiang Street, Dongcheng District, Beijing, 100730, China
| | - Jieting Peng
- Eye College of Chengdu University of TCM, Chengdu, Sichuan, China
| | - Kai Cao
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Ningli Wang
- Beijing Ophthalmology and Visual Sciences Key Lab, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, No. 1 Dongjiaominxiang Street, Dongcheng District, Beijing, 100730, China.
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
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Wang P, Jiang J, Kong K, Fang X, Song Y, Lin F, Jiang J, Zeng J, Chen S, Zhang X. Construction of glaucoma model and comparing eyeball enlargement with myopia in Guinea pig. Exp Eye Res 2024; 246:110010. [PMID: 39069000 DOI: 10.1016/j.exer.2024.110010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 07/09/2024] [Accepted: 07/22/2024] [Indexed: 07/30/2024]
Abstract
This study aimed to develop and evaluate a guinea pig model for glaucoma, comparing resultant eyeball enlargement with an existing myopia model. Thirty guinea pigs underwent intracameral injection of magnetic microspheres to induce chronic ocular hypertension (COH). Intraocular pressure (IOP) was systematically monitored, revealing a successful induction of COH in 73.33% of the guinea pigs. The mean IOP increased from a baseline of 18.04 ± 1.33 mmHg, reaching a peak at week 3 (36.31 ± 6.13 mmHg) and remaining elevated for at least 7 weeks. All data are presented as mean ± standard deviation of the mean. Subsequently, detailed assessments were conducted to validate the established glaucoma model. Immunofluorescent staining demonstrated a significant decrease in the density of retinal ganglion cells (RGC) in the glaucoma group. Optic disc excavation and notable thinning of the lamina cribrosa (LC) were observed. The quantity of optic nerve ax·ons in glaucoma group gradually decreased from baseline (44553 ± 3608/mm2) to week 4 (28687 ± 2071/mm2) and week 8 (17977 ± 3697/mm2). Moreover, regarding the global enlargement of eyeballs, both the transverse and longitudinal axis in glaucomatous eyes were found to be significantly larger than that in myopic eyes, particularly in the anterior chamber depth (1.758 ± 0.113 mm vs. 1.151 ± 0.046 mm). These findings indicate distinct patterns of structural changes associated with glaucoma and myopia in the guinea pig model. This guinea pig model holds promise for future research aimed at exploring biomechanical mechanisms, therapeutic interventions, and advancing our understanding of the relationship between glaucoma and myopia.
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Affiliation(s)
- Peiyuan Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Jiaxuan Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Kangjie Kong
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Xiuli Fang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Yunhe Song
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Fengbin Lin
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Jingwen Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Junwen Zeng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China.
| | - Shida Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China.
| | - Xiulan Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China.
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Okon MD, Ma Y, Nguyen-Rudy BA, Roberts CJ. A New Biomechanical Deformation Response Parameter: Change in Central Corneal Thickness During Air Puff Induced Corneal Deformation. Curr Eye Res 2024; 49:798-802. [PMID: 38629736 PMCID: PMC11254558 DOI: 10.1080/02713683.2024.2338228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/28/2024] [Indexed: 07/18/2024]
Abstract
PURPOSE To investigate the percent change in central corneal thickness (%ΔCCT) during air-puff-induced deformation as an indicator of corneal biomechanical response. METHODS Forty ex vivo human eyes from forty donors were imaged using the CorVis ST at experimentally controlled intraocular pressure (IOP) of 10, 20, 30, and 40 mmHg, followed by uniaxial strip testing to calculate tensile modulus. The CorVis ST research software tracked the anterior and posterior cornea edges and determined the dynamic corneal response (DCR) parameters. Eyes were excluded if image quality or posterior tracking issues were present. Custom algorithms were used to calculate CCT during deformation using a ray-tracing method to correct for Scheimpflug and optical distortion within each image. Correlation and stepwise regression analyses between the shape-related DCR parameters and %ΔCCT were conducted. A mixed model analysis was performed to test the effect of IOP and the strongest significant predictors of the stepwise regression on %ΔCCT. The significance threshold was set to p < 0.05. RESULTS Thirty eyes were ultimately analyzed and CCT increased significantly from the pre-deformation state to the highest concavity state at each IOP level (p < 0.001). IOP and multiple shape DCRs were found to be significantly related to %ΔCCT (p < 0.0001). The strongest predictor of %ΔCCT was integrated inverse radius (IIR) (p < 0.0001; partial R2 = 0.4772) with no other parameter having a partial R2 value greater than 0.04. The mixed model analysis showed that IIR was the sole predictor (p = 0.0098) and IOP was no longer significant as a single predictor. However, the interaction of IIR with IOP (p = 0.0023) had a significant effect on %ΔCCT. CONCLUSION Percent change in CCT is influenced by corneal stiffness as indicated by the significant relationship with IIR. The %ΔCCT may be a potential biomarker for determining differences in corneal deformation response with corneal diseases.
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Affiliation(s)
- Monica D. Okon
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Yanhui Ma
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
| | | | - Cynthia J. Roberts
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
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De La Hoz A, Villegas L, Marcos S, Birkenfeld JS. A simple computational model for scleral stiffness assessments via air-puff deformation OCT. Front Bioeng Biotechnol 2024; 12:1426060. [PMID: 39144479 PMCID: PMC11323745 DOI: 10.3389/fbioe.2024.1426060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Accepted: 07/16/2024] [Indexed: 08/16/2024] Open
Abstract
Introduction: The mechanical properties of the sclera are related to its structural function, and changes to these properties are believed to contribute to pathologies such as myopia. Air-puff deformation imaging is a tool that uses an imaging system coupled with an air-puff excitation source to induce and measure deformation in a tissue in vivo. Typically used for the study of the cornea's mechanical properties and IOP, this tool has been proposed as a method to evaluate scleral stiffness. Methods: In this work, we present a computational model of the rabbit eye to assess scleral deformation under air-puff. Parametric studies were conducted to evaluate the effects of material properties, intraocular pressure, and other parameters on the deformation response. Output from the model was also compared to experimental measurements of air-puff deformation in rabbit eyes under varying IOP. Results: Central deformation response was found to be most influenced by material properties of the sclera (at site of air-puff and posterior), thickness, and IOP, whereas deformation profile was most influenced by material properties. Experimental and simulated IOP dependence were found to be similar (RMSE = 0.13 mm). Discussion: Scleral APDI could be a useful tool for quick in vivo assessment of scleral stiffness.
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Affiliation(s)
- Andres De La Hoz
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Lupe Villegas
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Susana Marcos
- Center for Visual Science, The Institute of Optics, Flaum Eye Institute, University of Rochester, Rochester, NY, United States
| | - Judith S. Birkenfeld
- Instituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
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Yii F, Strang N, Bernabeu MO, Dhillon B, MacGillivray T. Corneal biomechanics are not exclusively compromised in high myopia. Ophthalmic Physiol Opt 2024; 44:977-986. [PMID: 38563586 DOI: 10.1111/opo.13313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 03/15/2024] [Accepted: 03/22/2024] [Indexed: 04/04/2024]
Abstract
INTRODUCTION Research assuming linearity has concluded that corneal biomechanics are compromised in high myopia. We investigated whether this assumption was appropriate and re-examined these associations across different levels of myopia. METHODS Myopic (spherical equivalent refraction, SER ≤ -0.50 D) eyes of 10,488 adults aged 40-69 years without any history of systemic and ocular conditions were identified in the UK Biobank. Ordinary least squares (OLS) regression was employed to test the linear association between corneal hysteresis (CH) or corneal resistance factor (CRF), separately, and SER while controlling for age, sex, corneal radius and intraocular pressure. Quantile regression (QR) was used to test the same set of associations across 49 equally spaced conditional quantiles of SER. RESULTS In OLS regression, each standard deviation (SD) decrease in CH and CRF was associated with 0.08 D (95% CI: 0.04-0.12; p < 0.001) and 0.10 D (95% CI: 0.04-0.15; p < 0.001) higher myopia, respectively. However, residual analysis indicated that the linearity assumption was violated. QR revealed no evidence of a significant association between CH/CRF and SER in low myopia, but a significant (p < 0.05) positive association became evident from -2.78 D (0.06 and 0.08 D higher myopia per SD decrease in CH and CRF). The magnitude of association increased exponentially with increasing myopia: in the -5.03 D quantile, every SD decrease in CH and CRF was associated with 0.17 D (95% CI: 0.08-0.25; p < 0.001) and 0.21 D (95% CI: 0.10-0.31; p < 0.001) higher myopia. In the -8.63 D quantile, this further increased to 0.54 D (95% CI: 0.33-0.76; p < 0.001) and 0.67 D (95% CI: 0.41-0.93; p < 0.001) higher myopia per SD decrease in CH and CRF. CONCLUSIONS Corneal biomechanics appeared compromised from around -3.00 D. These changes were observed to be exponential with increasing myopia.
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Affiliation(s)
- Fabian Yii
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK
- Curle Ophthalmology Laboratory, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
| | - Niall Strang
- Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Miguel O Bernabeu
- Centre for Medical Informatics, Usher Institute, The University of Edinburgh, Edinburgh, UK
- The Bayes Centre, The University of Edinburgh, Edinburgh, UK
| | - Baljean Dhillon
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK
- Curle Ophthalmology Laboratory, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
- Princess Alexandra Eye Pavilion, NHS Lothian, Edinburgh, UK
| | - Tom MacGillivray
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK
- Curle Ophthalmology Laboratory, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
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Aoki S, Asaoka R, Azuma K, Kitamoto K, Ueda K, Inoue T, Obata R. Biomechanical properties measured with dynamic Scheimpflug analyzer in central serous chorioretinopathy. Graefes Arch Clin Exp Ophthalmol 2024; 262:1795-1803. [PMID: 38285248 PMCID: PMC11106119 DOI: 10.1007/s00417-024-06378-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 01/09/2024] [Accepted: 01/16/2024] [Indexed: 01/30/2024] Open
Abstract
PURPOSE Recent evidence suggests that venous congestion at the vortex vein significantly contributes to the development of central serous chorioretinopathy (CSCR), and sclera is observed to be thicker in affected eyes. This study aims to investigate whether eyes with CSCR exhibit stiff corneas, measured using Corneal Visualization Scheimflug Technology (Corvis ST), which may serve as an indicator of scleral stiffness. METHODS This retrospective case-control study comprises 52 eyes from 33 patients diagnosed with CSCR and 52 eyes from 32 normal controls without CSCR. We compared biomechanical parameters measured with Corvis ST and anterior scleral thickness measured using anterior segment swept-source optical coherence tomography between the two groups. RESULTS Age, sex, axial length, intraocular pressure, and central corneal thickness showed no significant differences between the two groups (p > 0.05, linear mixed model). Three biomechanical parameters-peak distance, maximum deflection amplitude, and integrated inverse radius-indicated less deformability in CSCR eyes compared to control eyes. The stress-strain index (SSI), a measure of stiffness, and anterior scleral thickness (AST) at temporal and nasal points were significantly higher in the CSCR eyes. SSI and AST were not correlated, yet both were significantly and independently associated with CSCR in a multivariate logistic regression model. CONCLUSIONS Eyes affected by CSCR have stiffer corneas, irrespective of thicker scleral thickness. This suggests that stiffer sclera may play a role in the pathogenesis of CSCR.
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Grants
- 19H01114 Ministry of Education, Culture, Sports, Science and Technology
- 18KK0253 the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 20K09784 the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 21K16870 the Ministry of Education, Culture, Sports, Science and Technology of Japan
- The University of Tokyo
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Affiliation(s)
- Shuichiro Aoki
- The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8655, Japan.
| | - Ryo Asaoka
- Seirei Christopher University, Hamamatsu, Japan
| | - Keiko Azuma
- The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8655, Japan
| | - Kohdai Kitamoto
- The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8655, Japan
| | - Kohei Ueda
- The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8655, Japan
| | | | - Ryo Obata
- The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8655, Japan
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Harvey DH, Roberts CJ, Mahmoud AM, Nuñez FM, Ma Y, Fleming GP. Biomechanical and Vascular Metrics Between Eyes of Patients With Asymmetric Glaucoma and Symmetric Glaucoma. J Glaucoma 2024; 33:334-339. [PMID: 38194297 PMCID: PMC11052687 DOI: 10.1097/ijg.0000000000002363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 11/25/2023] [Indexed: 01/10/2024]
Abstract
PRCIS Corneal hysteresis (CH) and pulsatile ocular blood volume (POBV) were significantly lower in the eye with greater damage in asymmetric glaucoma, without a difference in intraocular pressure (IOP) or central corneal thickness (CCT), and no difference in elastic parameters. OBJECTIVE To compare biomechanical and vascular metrics between the eyes of patients with asymmetric glaucoma (ASYMM) and those with symmetric glaucoma (SYMM). PATIENTS AND METHODS Forty-five patients were prospectively recruited and divided into ASYMM, defined as cup-to-disc (C/D) ratio difference >0.1 between eyes and SYMM, with C/D difference ≤0.1. For ASYMM, the smaller C/D was defined as the best eye ("best") and the fellow eye was defined as the worst eye ("worse"). All metrics were subtracted as "worse" minus "best," including the viscoelastic parameter CH, and elastic parameters from the Corvis ST, including stiffness parameter at first applanation, stiffness parameter at highest concavity, integrated inverse radius, deformation amplitude ratio, IOP, CCT, mean deviation (MD), ganglion cell complex (GCC), and POBV were included. Paired t tests were performed between eyes in both groups. Statistical analyses were performed with SAS using a significance threshold of P <0.05. RESULTS For ASYMM (16 patients), "worse" showed significantly lower CH (-0.76 ± 1.22), POBV (-0.38 ± 0.305), MD (-3.66 ± 6.55), and GCC (-7.9 ± 12.2) compared with "best." No other parameters were significantly different. For SYMM (29 patients), there were no significantly different metrics between eyes. CONCLUSIONS Lower CH, POBV, GCC, and worse MD were associated with greater glaucomatous damage in asymmetric glaucoma without a difference in IOP or CCT. Lower CH and GCC are consistent with previous studies. POBV, a new clinical parameter that may indicate reduced blood flow, is also associated with greater damage.
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Affiliation(s)
| | - Cynthia J Roberts
- Ophthalmology and Visual Sciences, The Ohio State University
- Biomedical Engineering, The Ohio State University
| | - Ashraf M Mahmoud
- Ophthalmology and Visual Sciences, The Ohio State University
- Biomedical Engineering, The Ohio State University
| | | | - Yanhui Ma
- Ophthalmology and Visual Sciences, The Ohio State University
| | - Gloria P Fleming
- Ophthalmology and Visual Sciences, The Ohio State University
- Biomedical Engineering, The Ohio State University
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Yii FS, He M, Chappell F, Bernabeu MO, MacGillivray T, Dhillon B, Tatham A, Strang N. Higher intraocular pressure is associated with slower axial growth in children with non-pathological high myopia. Eye (Lond) 2024; 38:1208-1214. [PMID: 38081936 PMCID: PMC11009290 DOI: 10.1038/s41433-023-02872-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 11/21/2023] [Accepted: 11/23/2023] [Indexed: 04/13/2024] Open
Abstract
OBJECTIVES To investigate the association between intraocular pressure (IOP) and axial elongation rate in highly myopic children from the ZOC-BHVI High Myopia Cohort Study. METHODS 162 eyes of 81 healthy children (baseline spherical equivalent: -6.25 D to -15.50 D) aged 7-12 years with non-pathological high myopia were studied over five biennial visits. The mean (SD) follow-up duration was 5.2 (3.3) years. A linear mixed-effects model (LMM) was used to assess the association between IOP (at time point t-1) and axial elongation rate (annual rate of change in AL from t-1 to t), controlling for a pre-defined set of covariates including sex, age, central corneal thickness, anterior chamber depth and lens thickness (at t-1). LMM was also used to assess the contemporaneous association between IOP and axial length (AL) at t, controlling for the same set of covariates (at t) as before. RESULTS Higher IOP was associated with slower axial growth (β = -0.01, 95% CI -0.02 to -0.005, p = 0.001). There was a positive contemporaneous association between IOP and AL (β = 0.03, 95% CI 0.01-0.05, p = 0.004), but this association became progressively less positive with increasing age, as indicated by a negative interaction effect between IOP and age on AL (β = -0.01, 95% CI -0.01 to -0.003, p = 0.001). CONCLUSIONS Higher IOP is associated with slower rather than faster axial growth in children with non-pathological high myopia, an association plausibly confounded by the increased influence of ocular compliance on IOP.
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Affiliation(s)
- Fabian Sl Yii
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK.
- Curle Ophthalmology Laboratory, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK.
| | - Mingguang He
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
- Centre for Eye Research Australia, The University of Melbourne, Melbourne, Australia
| | - Francesca Chappell
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK
| | - Miguel O Bernabeu
- Centre for Medical Informatics, Usher Institute, The University of Edinburgh, Edinburgh, UK
- The Bayes Centre, The University of Edinburgh, Edinburgh, UK
| | - Tom MacGillivray
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK
- Curle Ophthalmology Laboratory, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
| | - Baljean Dhillon
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK
- Curle Ophthalmology Laboratory, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
- Princess Alexandra Eye Pavilion, NHS Lothian, Edinburgh, UK
| | - Andrew Tatham
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, UK
- Princess Alexandra Eye Pavilion, NHS Lothian, Edinburgh, UK
| | - Niall Strang
- Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK
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10
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Gómez C, Piñero DP, Paredes M, Alió JL, Cavas F. Study of the Influence of Boundary Conditions on Corneal Deformation Based on the Finite Element Method of a Corneal Biomechanics Model. Biomimetics (Basel) 2024; 9:73. [PMID: 38392119 PMCID: PMC10886865 DOI: 10.3390/biomimetics9020073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 01/15/2024] [Accepted: 01/18/2024] [Indexed: 02/24/2024] Open
Abstract
Implementing in silico corneal biomechanical models for surgery applications can be boosted by developing patient-specific finite element models adapted to clinical requirements and optimized to reduce computational times. This research proposes a novel corneal multizone-based finite element model with octants and circumferential zones of clinical interest for material definition. The proposed model was applied to four patient-specific physiological geometries of keratoconus-affected corneas. Free-stress geometries were calculated by two iterative methods, the displacements and prestress methods, and the influence of two boundary conditions: embedded and pivoting. The results showed that the displacements, stress and strain fields differed for the stress-free geometry but were similar and strongly depended on the boundary conditions for the estimated physiological geometry when considering both iterative methods. The comparison between the embedded and pivoting boundary conditions showed bigger differences in the posterior limbus zone, which remained closer in the central zone. The computational calculation times for the stress-free geometries were evaluated. The results revealed that the computational time was prolonged with disease severity, and the displacements method was faster in all the analyzed cases. Computational times can be reduced with multicore parallel calculation, which offers the possibility of applying patient-specific finite element models in clinical applications.
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Affiliation(s)
- Carmelo Gómez
- International School of Doctorate, Technical University of Cartagena, 30202 Cartagena, Spain
| | - David P Piñero
- Department of Optics, Pharmacology and Anatomy, University of Alicante, 03690 Alicante, Spain
| | - Manuel Paredes
- ICA, Université de Toulouse, UPS, INSA, ISAE-SUPAERO, MINES-ALBI, CNRS, 3 rue Caroline Aigle, 31400 Toulouse, France
| | - Jorge L Alió
- Cornea, Cataract and Refractive Surgery Department, VISSUM, 03016 Alicante, Spain
- Division of Ophthalmology, Department of Pathology and Surgery, Faculty of Medicine, Miguel Hernández University, 03202 Alicante, Spain
| | - Francisco Cavas
- Department of Structures, Construction and Graphic Expression, Technical University of Cartagena, 30202 Cartagena, Spain
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11
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Roy D, Basu S. Future research perspective on the interfacial physics of non-invasive glaucoma testing in pathogen transmission from the eyes. Biointerphases 2024; 19:018501. [PMID: 38407471 DOI: 10.1116/6.0003347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 01/25/2024] [Indexed: 02/27/2024] Open
Abstract
Non-contact tonometry (NCT) is a non-invasive ophthalmologic technique to measure intraocular pressure (IOP) using an air puff for routine glaucoma testing. Although IOP measurement using NCT has been perfected over many years, various phenomenological aspects of interfacial physics, fluid structure interaction, waves on corneal surface, and pathogen transmission routes to name a few are inherently unexplored. Research investigating the interdisciplinary physics of the ocular biointerface and of the NCT procedure is sparse and hence remains to be explored in sufficient depth. In this perspective piece, we introduce NCT and propose future research prospects that can be undertaken for a better understanding of the various hydrodynamic processes that occur during NCT from a pathogen transmission viewpoint. In particular, the research directions include the characterization and measurement of the incoming air puff, understanding the complex fluid-solid interactions occurring between the air puff and the human eye for measuring IOP, investigating the various waves that form and travel; tear film breakup and subsequent droplet formation mechanisms at various spatiotemporal length scales. Further, from an ocular disease transmission perspective, the disintegration of the tear film into droplets and aerosols poses a potential pathogen transmission route during NCT for pathogens residing in nasolacrimal and nasopharynx pathways. Adequate precautions by opthalmologist and medical practioners are therefore necessary to conduct the IOP measurements in a clinically safer way to prevent the risk associated with pathogen transmission from ocular diseases like conjunctivitis, keratitis, and COVID-19 during the NCT procedure.
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Affiliation(s)
- Durbar Roy
- Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Saptarshi Basu
- Department of Mechanical Engineering, Indian Institute of Science, Bengaluru, Karnataka 560012, India
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12
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Glover K, Mishra D, Gade S, Vora LK, Wu Y, Paredes AJ, Donnelly RF, Singh TRR. Microneedles for advanced ocular drug delivery. Adv Drug Deliv Rev 2023; 201:115082. [PMID: 37678648 DOI: 10.1016/j.addr.2023.115082] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/15/2023] [Accepted: 08/22/2023] [Indexed: 09/09/2023]
Abstract
In the field of ocular drug delivery, topical delivery remains the most common treatment option for managing anterior segment diseases, whileintraocular injectionsare the current gold standard treatment option for treating posterior segment diseases. Nonetheless, topical eye drops are associated with low bioavailability (<5%), and theintravitreal administration procedure is highly invasive, yielding poor patient acceptability. In both cases, frequent administration is currently required. As a result, there is a clear unmet need for sustained drug delivery to the eye, particularly in a manner that can be localised. Microneedles, which are patches containing an array of micron-scale needles (<1 mm), have the potential to meet this need. These platforms can enable localised drug delivery to the eye while enhancing penetration of drug molecules through key ocular barriers, thereby improving overall therapeutic outcomes. Moreover, the minimally invasive manner in which microneedles are applied could provide significant advantages over traditional intravitreal injections regarding patient acceptability. Considering the benefitsofthis novel ocular delivery system, this review provides an in-depth overviewofthe microneedle systems for ocular drug delivery, including the types of microneedles used and therapeutics delivered. Notably, we outline and discuss the current challenges associated with the clinical translation of these platforms and offer opinions on factors which should be considered to improve such transition from lab to clinic.
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Affiliation(s)
- Katie Glover
- School of Pharmacy, Queen's University Belfast, Medical Biology Centre, Belfast, UK
| | - Deepakkumar Mishra
- School of Pharmacy, Queen's University Belfast, Medical Biology Centre, Belfast, UK
| | - Shilpkala Gade
- School of Pharmacy, Queen's University Belfast, Medical Biology Centre, Belfast, UK
| | - Lalitkumar K Vora
- School of Pharmacy, Queen's University Belfast, Medical Biology Centre, Belfast, UK
| | - Yu Wu
- School of Pharmacy, Queen's University Belfast, Medical Biology Centre, Belfast, UK
| | - Alejandro J Paredes
- School of Pharmacy, Queen's University Belfast, Medical Biology Centre, Belfast, UK
| | - Ryan F Donnelly
- School of Pharmacy, Queen's University Belfast, Medical Biology Centre, Belfast, UK
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13
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Brazuna R, Alonso RS, Salomão MQ, Fernandes BF, Ambrósio R. Ocular Biomechanics and Glaucoma. Vision (Basel) 2023; 7:vision7020036. [PMID: 37218954 DOI: 10.3390/vision7020036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 04/11/2023] [Accepted: 04/21/2023] [Indexed: 05/24/2023] Open
Abstract
Biomechanics is a branch of biophysics that deals with mechanics applied to biology. Corneal biomechanics have an important role in managing patients with glaucoma. While evidence suggests that patients with thin and stiffer corneas have a higher risk of developing glaucoma, it also influences the accurate measurement of intraocular pressure. We reviewed the pertinent literature to help increase our understanding of the biomechanics of the cornea and other ocular structures and how they can help optimize clinical and surgical treatments, taking into consideration individual variabilities, improve the diagnosis of suspected patients, and help monitor the response to treatment.
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Affiliation(s)
- Rodrigo Brazuna
- Department of Ophthalmology, Federal University of the State of Rio de Janeiro, Rio de Janeiro 22290-240, RJ, Brazil
| | - Ruiz S Alonso
- Department of Ophthalmology, Antonio Pedro University Hospital, Fluminense Federal University, Niterói 24033-900, RJ, Brazil
| | - Marcella Q Salomão
- Department of Ophthalmology, Federal University of São Paulo, São Paulo 04023-062, SP, Brazil
| | | | - Renato Ambrósio
- Department of Ophthalmology, Federal University of the State of Rio de Janeiro, Rio de Janeiro 22290-240, RJ, Brazil
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14
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Reilly MA, Katz SE, Roberts CJ. Orbital fat swelling: A biomechanical theory and supporting model for spaceflight-associated neuro-ocular syndrome (SANS). Front Bioeng Biotechnol 2023; 11:1095948. [PMID: 36845176 PMCID: PMC9947460 DOI: 10.3389/fbioe.2023.1095948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 01/30/2023] [Indexed: 02/11/2023] Open
Abstract
Spaceflight-Associated Neuro-ocular Syndrome (SANS) is a descriptor of several ocular and visual signs and symptoms which commonly afflicts those exposed to microgravity. We propose a new theory for the driving force leading to the development of Spaceflight-Associated Neuro-ocular Syndrome which is described via a finite element model of the eye and orbit. Our simulations suggest that the anteriorly directed force produced by orbital fat swelling is a unifying explanatory mechanism for Spaceflight-Associated Neuro-ocular Syndrome, as well as producing a larger effect than that generated by elevation in intracranial pressure. Hallmarks of this new theory include broad flattening of the posterior globe, loss of tension in the peripapillary choroid, decreased axial length, consistent with findings in astronauts. A geometric sensitivity study suggests several anatomical dimensions may be protective against Spaceflight-Associated Neuro-ocular Syndrome.
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Affiliation(s)
- Matthew A. Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States,Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, United States,*Correspondence: Matthew A. Reilly,
| | - Steven E. Katz
- Ohio Neuro-Ophthalmology, Orbital Disease & Oculoplastics, Columbus, OH, United States
| | - Cynthia J. Roberts
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States,Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, United States
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15
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Yuhas PT, Roberts CJ. Clinical Ocular Biomechanics: Where Are We after 20 Years of Progress? Curr Eye Res 2023; 48:89-104. [PMID: 36239188 DOI: 10.1080/02713683.2022.2125530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Purpose: Ocular biomechanics is an assessment of the response of the structures of the eye to forces that may lead to disease development and progression, or influence the response to surgical intervention. The goals of this review are (1) to introduce basic biomechanical principles and terminology, (2) to provide perspective on the progress made in the clinical study and assessment of ocular biomechanics, and (3) to highlight critical studies conducted in keratoconus, laser refractive surgery, and glaucoma in order to aid interpretation of biomechanical parameters in the laboratory and in the clinic.Methods: A literature review was first conducted of basic biomechanical studies related to ocular tissue. The subsequent review of ocular biomechanical studies was limited to those focusing on keratoconus, laser refractive surgery, or glaucoma using the only two commercially available devices that allow rapid assessment of biomechanical response in the clinic.Results: Foundational studies on ocular biomechanics used a combination of computer modeling and destructive forces on ex-vivo tissues. The knowledge gained from these studies could not be directly translated to clinical research and practice until the introduction of non-contact tonometers that quantified the deformation response of the cornea to an air puff, which represents a non-destructive, clinically appropriate load. The corneal response includes a contribution from the sclera which may limit corneal deformation. Two commercial devices are available, the Ocular Response Analyzer which produces viscoelastic parameters with a customized load for each eye, and the Corvis ST which produces elastic parameters with a consistent load for every eye. Neither device produces the classic biomechanical properties reported in basic studies, but rather biomechanical deformation response parameters which require careful interpretation.Conclusions: Research using clinical tools has enriched our understanding of how ocular disease alters ocular biomechanics, as well as how ocular biomechanics may influence the pathophysiology of ocular disease and response to surgical intervention.
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Affiliation(s)
- Phillip T Yuhas
- College of Optometry, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH, USA
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16
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Lombardo G, Bernava GM, Serrao S, Lombardo M. Theranostic-guided corneal cross-linking: Preclinical evidence on a new treatment paradigm for keratoconus. JOURNAL OF BIOPHOTONICS 2022; 15:e202200218. [PMID: 36059083 DOI: 10.1002/jbio.202200218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 06/15/2023]
Abstract
Theranostics is an emerging therapeutic paradigm of personalized medicine; the term refers to the simultaneous integration of therapy and diagnostics. In this work, theranostic-guided corneal cross-linking was performed on 10 human sclero-corneal tissues. The samples were soaked with 0.22% riboflavin formulation and underwent 9 minutes UV-A irradiance at 10 mW/cm2 using theranostic device, which provided both a measure of corneal riboflavin concentration and a theranostic score estimating treatment efficacy in real time. A three-element viscoelastic model was developed to fit the deformation response of the cornea to air-puff excitation of dynamic tonometry and to calculate the mean corneal stiffness parameter before and after treatment. Significant correlation was found between the theranostic score and the increase in mean corneal stiffness (R = 0.80; P < .001). Accuracy and precision of the theranostic score in predicting the induced corneal tissue stiffening were both 90%. The riboflavin concentration prior to starting the UV-A photo-therapy phase was the most important variable to allow corneal cross-linking to be effective. Theranostic UV-A light mediated imaging and therapy enables the operator to adopt a precise approach for achieving highly predictable biomechanical strengthening on individual corneas.
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Affiliation(s)
- Giuseppe Lombardo
- CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F, Messina, Italy
- Vision Engineering Italy srl, Rome, Italy
| | | | | | - Marco Lombardo
- Vision Engineering Italy srl, Rome, Italy
- Studio Italiano di Oftalmologia, Rome, Italy
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17
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Zhao Y, Hu G, Yan Y, Wang Z, Liu X, Shi H. Biomechanical analysis of ocular diseases and its in vitro study methods. Biomed Eng Online 2022; 21:49. [PMID: 35870978 PMCID: PMC9308301 DOI: 10.1186/s12938-022-01019-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 07/13/2022] [Indexed: 12/25/2022] Open
Abstract
Ocular diseases are closely related to the physiological changes in the eye sphere and its contents. Using biomechanical methods to explore the relationship between the structure and function of ocular tissue is beneficial to reveal the pathological processes. Studying the pathogenesis of various ocular diseases will be helpful for the diagnosis and treatment of ocular diseases. We provide a critical review of recent biomechanical analysis of ocular diseases including glaucoma, high myopia, and diabetes. And try to summarize the research about the biomechanical changes in ocular tissues (e.g., optic nerve head, sclera, cornea, etc.) associated with those diseases. The methods of ocular biomechanics research in vitro in recent years are also reviewed, including the measurement of biomechanics by ophthalmic equipment, finite element modeling, and biomechanical analysis methods. And the preparation and application of microfluidic eye chips that emerged in recent years were summarized. It provides new inspiration and opportunity for the pathogenesis of eye diseases and personalized and precise treatment.
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18
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McAuley R, Nolan A, Curatolo A, Alexandrov S, Zvietcovich F, Varea Bejar A, Marcos S, Leahy M, Birkenfeld JS. Co-axial acoustic-based optical coherence vibrometry probe for the quantification of resonance frequency modes in ocular tissue. Sci Rep 2022; 12:18834. [PMID: 36336702 PMCID: PMC9637745 DOI: 10.1038/s41598-022-21978-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 10/07/2022] [Indexed: 11/08/2022] Open
Abstract
We present a co-axial acoustic-based optical coherence vibrometry probe (CoA-OCV) for vibro-acoustic resonance quantification in biological tissues. Sample vibrations were stimulated via a loudspeaker, and pre-compensation was used to calibrate the acoustic spectrum. Sample vibrations were measured via phase-sensitive swept-source optical coherence tomography (OCT). Resonance frequencies of corneal phantoms were measured at varying intraocular pressures (IOP), and dependencies on Young´s Modulus (E), phantom thickness and IOP were observed. Cycling IOP revealed hysteresis. For E = 0.3 MPa, resonance frequencies increased with IOP at a rate of 3.9, 3.7 and 3.5 Hz/mmHg for varied thicknesses and 1.7, 2.5 and 2.8 Hz/mmHg for E = 0.16 MPa. Resonance frequencies increased with thickness at a rate of 0.25 Hz/µm for E = 0.3 MPa, and 0.40 Hz/µm for E = 0.16 MPa. E showed the most predominant impact in the shift of the resonance frequencies. Full width at half maximum (FWHM) of the resonance modes increased with increasing thickness and decreased with increasing E. Only thickness and E contributed to the variance of FWHM. In rabbit corneas, resonance frequencies of 360-460 Hz were observed. The results of the current study demonstrate the feasibility of CoA-OCV for use in future OCT-V studies.
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Affiliation(s)
- Ryan McAuley
- Tissue Optics and Microcirculation Imaging Facility, School of Physics, University of Galway, Galway, Ireland.
| | - A Nolan
- Tissue Optics and Microcirculation Imaging Facility, School of Physics, University of Galway, Galway, Ireland
| | - A Curatolo
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
- International Centre for Translational Eye Research, Warsaw, Poland
| | - S Alexandrov
- Tissue Optics and Microcirculation Imaging Facility, School of Physics, University of Galway, Galway, Ireland
| | - F Zvietcovich
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - A Varea Bejar
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - S Marcos
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
- Center for Visual Science, The Institute of Optics, Flaum Eye Institute, University of Rochester, Rochester, New York, USA
| | - M Leahy
- Tissue Optics and Microcirculation Imaging Facility, School of Physics, University of Galway, Galway, Ireland
| | - J S Birkenfeld
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain.
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19
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Redaelli E, Grasa J, Calvo B, Rodriguez Matas JF, Luraghi G. A detailed methodology to model the Non Contact Tonometry: a Fluid Structure Interaction study. Front Bioeng Biotechnol 2022; 10:981665. [PMID: 36267451 PMCID: PMC9576856 DOI: 10.3389/fbioe.2022.981665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/13/2022] [Indexed: 11/21/2022] Open
Abstract
Understanding the corneal mechanical properties has great importance in the study of corneal pathologies and the prediction of refractive surgery outcomes. Non-Contact Tonometry (NCT) is a non-invasive diagnostic tool intended to characterize the corneal tissue response in vivo by applying a defined air-pulse. The biomarkers inferred from this test can only be considered as indicators of the global biomechanical behaviour rather than the intrinsic biomechanical properties of the corneal tissue. A possibility to isolate the mechanical response of the corneal tissue is the use of an inverse finite element method, which is based on accurate and reliable modelling. Since a detailed methodology is still missing in the literature, this paper aims to construct a high-fidelity finite-element model of an idealized 3D eye for in silico NCT. A fluid-structure interaction (FSI) simulation is developed to virtually apply a defined air-pulse to a 3D idealized eye model comprising cornea, limbus, sclera, lens and humors. Then, a sensitivity analysis is performed to examine the influence of the intraocular pressure (IOP) and the structural material parameters on three biomarkers associated with corneal deformation. The analysis reveals the requirements for the in silico study linked to the correct reproduction of three main aspects: the air pressure over the cornea, the biomechanical properties of the tissues, and the IOP. The adoption of an FSI simulation is crucial to capture the correct air pressure profile over the cornea as a consequence of the air-jet. Regarding the parts of the eye, an anisotropic material should be used for the cornea. An important component is the sclera: the stiffer the sclera, the lower the corneal deformation due to the air-puff. Finally, the fluid-like behavior of the humors should be considered in order to account for the correct variation of the IOP during the test which will, otherwise, remain constant. The development of a strong FSI tool amenable to model coupled structures and fluids provides the basis to find the biomechanical properties of the corneal tissue in vivo.
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Affiliation(s)
- Elena Redaelli
- Aragón Institute of Engineering Research (I3A), University of Zaragoza, Zaragoza, Spain
- *Correspondence: Elena Redaelli,
| | - Jorge Grasa
- Aragón Institute of Engineering Research (I3A), University of Zaragoza, Zaragoza, Spain
- Centro de Investigación Biomecánica en Red en Bioingenieria, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
| | - Begoña Calvo
- Aragón Institute of Engineering Research (I3A), University of Zaragoza, Zaragoza, Spain
- Centro de Investigación Biomecánica en Red en Bioingenieria, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
| | - Jose Felix Rodriguez Matas
- LaBS, Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milan, Italy
| | - Giulia Luraghi
- LaBS, Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milan, Italy
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20
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Vinas-Pena M, Feng X, Li GY, Yun SH. In situ measurement of the stiffness increase in the posterior sclera after UV-riboflavin crosslinking by optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2022; 13:5434-5446. [PMID: 36425630 PMCID: PMC9664890 DOI: 10.1364/boe.463600] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 08/08/2022] [Accepted: 08/09/2022] [Indexed: 06/16/2023]
Abstract
Scleral crosslinking may provide a way to prevent or treat myopia by stiffening scleral tissues. The ability to measure the stiffness of scleral tissues in situ pre and post scleral crosslinking would be useful but has not been established. Here, we tested the feasibility of optical coherence elastography (OCE) to measure shear modulus of scleral tissues and evaluate the impact of crosslinking on different posterior scleral regions using ex vivo porcine eyes as a model. From measured elastic wave speeds at 6 - 16 kHz, we obtained out-of-plane shear modulus value of 0.71 ± 0.12 MPa (n = 20) for normal porcine scleral tissues. After riboflavin-assisted UV crosslinking, the shear modulus increased to 1.50 ± 0.39 MPa (n = 20). This 2-fold change was consistent with the increase of static Young's modulus from 5.5 ± 1.1 MPa to 9.3 ± 1.9 MPa after crosslinking, which we measured using conventional uniaxial extensometry on tissue stripes. OCE revealed regional stiffness differences across the temporal, nasal, and deeper posterior sclera. Our results show the potential of OCE as a noninvasive tool to evaluate the effect of scleral crosslinking.
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Affiliation(s)
- Maria Vinas-Pena
- Wellman Center for Photomedicine and Harvard
Medical School, Massachusetts General Hospital, 50
Blossom St., Boston, MA, USA
| | - Xu Feng
- Wellman Center for Photomedicine and Harvard
Medical School, Massachusetts General Hospital, 50
Blossom St., Boston, MA, USA
| | - Guo-yang Li
- Wellman Center for Photomedicine and Harvard
Medical School, Massachusetts General Hospital, 50
Blossom St., Boston, MA, USA
| | - Seok-Hyun Yun
- Wellman Center for Photomedicine and Harvard
Medical School, Massachusetts General Hospital, 50
Blossom St., Boston, MA, USA
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21
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Foster WJ, Berg BW, Luminais SN, Hadayer A, Schaal S. Computational Modeling of Ophthalmic Procedures: Computational Modeling of Ophthalmic Procedures. Am J Ophthalmol 2022; 241:87-107. [PMID: 35358485 PMCID: PMC9444883 DOI: 10.1016/j.ajo.2022.03.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 01/16/2022] [Accepted: 03/17/2022] [Indexed: 11/01/2022]
Abstract
PURPOSE To explore how finite-element calculations can continue to contribute to diverse problems in ophthalmology and vision science, we describe our recent work on modeling the force on the peripheral retina in intravitreal injections and how that force increases with shorter, smaller gauge needles. We also present a calculation that determines the location and stress on a retinal pigment epithelial detachment during an intravitreal injection, the possibility that stress induced by the injection can lead to a tear of the retinal pigment epithelium. BACKGROUND Advanced computational models can provide a critical insight into the underlying physics in many surgical procedures, which may not be intuitive. METHODS The simulations were implemented using COMSOL Multiphysics. We compared the monkey retinal adhesive force of 18 Pa with the results of this study to quantify the maximum retinal stress that occurs during intravitreal injections. CONCLUSIONS Currently used 30-gauge needles produce stress on the retina during intravitreal injections that is only slightly below the limit that can create retinal tears. As retina specialists attempt to use smaller needles, the risk of complications may increase. In addition, we find that during an intravitreal injection, the stress on the retina in a pigment epithelial detachment occurs at the edge of the detachment (found clinically), and the stress is sufficient to tear the retina. These findings may guide physicians in future clinical research. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.
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Affiliation(s)
- William J Foster
- From the Department of Bioengineering (W.J.F.), Lewes Katz School of Medicine (B.W.B., S.N.L.), Temple University, Philadelphia, Pennsylvania, USA; Altasciences, Montréal, Québec, Canada (W.J.F.).
| | - Brian W Berg
- From the Department of Bioengineering (W.J.F.), Lewes Katz School of Medicine (B.W.B., S.N.L.), Temple University, Philadelphia, Pennsylvania, USA
| | - Steven N Luminais
- From the Department of Bioengineering (W.J.F.), Lewes Katz School of Medicine (B.W.B., S.N.L.), Temple University, Philadelphia, Pennsylvania, USA
| | - Amir Hadayer
- Department of Ophthalmology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel (A.H.)
| | - Shlomit Schaal
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts, USA (S.S.)
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22
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Jammal AA, Medeiros FA. Corneal Hysteresis and Rates of Neuroretinal Rim Change in Glaucoma. Ophthalmol Glaucoma 2022; 5:483-489. [PMID: 35331968 PMCID: PMC10278201 DOI: 10.1016/j.ogla.2022.03.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 06/14/2023]
Abstract
PURPOSE To evaluate the impact of corneal hysteresis (CH) as a risk factor for progressive neuroretinal rim loss in glaucoma, as measured by spectral-domain OCT of the Bruch's membrane opening minimum rim width (MRW). DESIGN Prospective, observational cohort study. PARTICIPANTS The study group included 118 eyes of 70 subjects with glaucoma. The average follow-up time for the cohort was 3.9 ± 1.3 years, with an average of 6.4 ± 2.0 spectral-domain OCT tests, ranging from 4 to 12. METHODS Corneal hysteresis measurements were acquired at baseline using the Ocular Response Analyzer (Reichert Instruments). Linear mixed models were used to investigate the relationship between the rates of MRW loss and baseline CH. Multivariable analyses adjusted for other putative predictive factors for progression, including mean intraocular pressure (IOP), central corneal thickness (CCT), age, race, and baseline disease severity. MAIN OUTCOME MEASURES Effects of CH on the rate of MRW change over time. RESULTS Corneal hysteresis had a significant effect on rates of MRW progression over time. Each 1-mmHg lower CH was associated with -0.38 μm/year faster MRW loss (95% confidence interval [CI], -0.70 to -0.06; P = 0.019), after adjustment for other predictive factors. The mean IOP was also significantly associated with progression, with -0.35 μm/year (95% CI, -0.47 to -0.23 μm/year) faster MRW change for each 1-mmHg higher pressure (P < 0.001). In the analysis of predictive strength, the mean IOP was the strongest predictive factor (R2 = 23%), followed by CH (R2 = 14%) and baseline disease severity (R2 = 6%). Central corneal thickness explained only 3% of the variability in slopes of change in global MRW. CONCLUSIONS Lower CH measurements were associated with faster loss of the neuroretinal rim in glaucoma, as measured by MRW. The predictive ability of CH was superior to that of CCT. These findings suggest that CH is an important parameter to be considered in assessing the risk of glaucoma progression.
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Affiliation(s)
- Alessandro A Jammal
- Vision, Imaging and Performance Laboratory, Duke Eye Center and Department of Ophthalmology, Duke University, Durham, North Carolina
| | - Felipe A Medeiros
- Vision, Imaging and Performance Laboratory, Duke Eye Center and Department of Ophthalmology, Duke University, Durham, North Carolina; Department of Electrical and Computer Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina.
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Brazuna R, Salomão M, Esporcatte B, Macedo M, Esporcatte L, Colombini GNUI, Ambrósio R. Corneal biomechanics and glaucoma beyond the bidirectional impact of intraocular pressure and corneal deformation response. REVISTA BRASILEIRA DE OFTALMOLOGIA 2022. [DOI: 10.37039/1982.8551.20220036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Abstract
PURPOSE OF THE REVIEW This review summarizes recent findings on corneal hysteresis, a biomechanical property of the cornea. Corneal hysteresis measurements can be easily acquired clinically and may serve as surrogate markers for biomechanical properties of tissues in the back of the eye, like the lamina cribrosa and peripapillary sclera, which may be related to the susceptibility to glaucomatous damage. RECENT FINDINGS Several studies have provided evidence of the associations between corneal hysteresis and clinically relevant outcomes in glaucoma. Corneal hysteresis has been shown to be predictive of glaucoma development in eyes suspected of having the disease. For eyes already diagnosed with glaucoma, lower corneal hysteresis has been associated with higher risk of progression and faster rates of visual field loss over time. Such associations appear to be stronger than those for corneal thickness, suggesting that corneal hysteresis may be a more important predictive factor. Recent evidence has also shown that cornealcorrected intraocular pressure measurements may present advantages compared to conventional Goldmann tonometry in predicting clinically relevant outcomes in glaucoma. SUMMARY Given the evidence supporting corneal hysteresis as an important risk factor for glaucoma development and its progression, practitioners should consider measuring corneal hysteresis in all patients at risk for glaucoma, as well as in those already diagnosed with the disease.
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Affiliation(s)
| | - Felipe A Medeiros
- Duke Eye Center and Department of Ophthalmology
- Department of Electrical and Computer Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina, USA
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Zhang D, Qin X, Zhang H, Li L. Time-varying regularity of changes in biomechanical properties of the corneas after removal of anterior corneal tissue. Biomed Eng Online 2021; 20:113. [PMID: 34801040 PMCID: PMC8606087 DOI: 10.1186/s12938-021-00948-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 11/03/2021] [Indexed: 11/13/2022] Open
Abstract
Background The corneal biomechanical properties with the prolongation of time after corneal refractive surgery are important for providing a mechanical basis for the occurrence of clinical phenomena such as iatrogenic keratectasia and refractive regression. The aim of this study was to explore the changes of corneal elastic modulus, and stress relaxation properties from the 6-month follow-up observations of rabbits after a removal of anterior corneal tissue in simulation to corneal refractive surgery. Methods The anterior corneal tissue, 6 mm in diameter and 30–50% of the original corneal thickness, the left eye of the rabbit was removed, and the right eye was kept as the control. The rabbits were normally raised and nursed for 6 months, during which corneal morphology data, and both of corneal hysteresis (CH) and corneal resistance factor (CRF) were gathered. Uniaxial tensile tests of corneal strips were performed at months 1, 3, and 6 from 7 animals, and corneal collagen fibrils were observed at months 1, 3, and 6 from 1 rabbit, respectively. Results Compared with the control group, there were statistical differences in the curvature radius at week 2 and month 3, and both CH and CRF at months 1, 2, and 6 in experiment group; there were statistical differences in elastic modulus at 1, 3, and month 6, and stress relaxation degree at month 3 in experiment group. The differences in corneal elastic modulus, stress relaxation degree and the total number of collagen fibrils between experiment and control groups varied gradually with time, and showed significant changes at the 3rd month after the treatment. Conclusions Corneas after a removal of anterior corneal tissue undergo dynamic changes in corneal morphology and biomechanical properties. The first 3 months after treatment could be a critical period. The variation of corneal biomechanical properties is worth considering in predicting corneal deformation after a removal of anterior corneal tissue.
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Affiliation(s)
- Di Zhang
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China.,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China
| | - Xiao Qin
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China.,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China
| | - Haixia Zhang
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China. .,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China.
| | - Lin Li
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China. .,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China.
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Bronte-Ciriza D, Birkenfeld JS, de la Hoz A, Curatolo A, Germann JA, Villegas L, Varea A, Martínez-Enríquez E, Marcos S. Estimation of scleral mechanical properties from air-puff optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2021; 12:6341-6359. [PMID: 34745741 PMCID: PMC8548012 DOI: 10.1364/boe.437981] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/15/2021] [Accepted: 08/15/2021] [Indexed: 05/11/2023]
Abstract
We introduce a method to estimate the biomechanical properties of the porcine sclera in intact eye globes ex vivo, using optical coherence tomography that is coupled with an air-puff excitation source, and inverse optimization techniques based on finite element modeling. Air-puff induced tissue deformation was determined at seven different locations on the ocular globe, and the maximum apex deformation, the deformation velocity, and the arc-length during deformation were quantified. In the sclera, the experimental maximum deformation amplitude and the corresponding arc length were dependent on the location of air-puff excitation. The normalized temporal deformation profile of the sclera was distinct from that in the cornea, but similar in all tested scleral locations, suggesting that this profile is independent of variations in scleral thickness. Inverse optimization techniques showed that the estimated scleral elastic modulus ranged from 1.84 ± 0.30 MPa (equatorial inferior) to 6.04 ± 2.11 MPa (equatorial temporal). The use of scleral air-puff imaging holds promise for non-invasively investigating the structural changes in the sclera associated with myopia and glaucoma, and for monitoring potential modulation of scleral stiffness in disease or treatment.
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Affiliation(s)
- David Bronte-Ciriza
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
- CNR - IPCF, Istituto per i Processi Chimico-Fisici, Messina, Italy
- Co-first authors
| | - Judith S Birkenfeld
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
- Co-first authors
| | - Andrés de la Hoz
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Andrea Curatolo
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
- International Centre for Translational Eye Research, Warsaw, Poland
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - James A Germann
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Lupe Villegas
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Alejandra Varea
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Eduardo Martínez-Enríquez
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
| | - Susana Marcos
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (IO-CSIC), Madrid, Spain
- Center for Visual Science, The Institute of Optics, Flaum Eye Institute, University of Rochester, NY 14642, USA
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Chen S, Jin Z, Zheng G, Ye S, Wang Y, Wang W, Wang Y, Zhu D, Shen M, Lu F. Diurnal variation of corneal elasticity in healthy young human using air-puff optical coherence elastography. JOURNAL OF BIOPHOTONICS 2021; 14:e202000440. [PMID: 33389817 DOI: 10.1002/jbio.202000440] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 12/15/2020] [Accepted: 12/30/2020] [Indexed: 06/12/2023]
Abstract
Due to the disruption of intraocular pressure (IOP) and central corneal thickness (CCT), diurnal variation in normal young human corneal elasticity is not clear. Using the custom-built air-puff optical coherence elastography, one eye of 21 normal subjects is enrolled randomly to measure the central corneal elasticity, IOP, and CCT in different time points within a day. Based on the multi-level model, the corneal elastic modulus is found to have a linear positive relation with IOP (P < .01) but not CCT (P = .175) and time point (P = .174-.686). A new indicator, corneal elasticity change rate, is proposed to present the magnitude of corneal elasticity change caused by 1 mmHg IOP, which can correct the interference effect of IOP. The results show that the corneal elasticity in the normal young human does not have the characteristics of diurnal variation under IOP control. Furthermore, IOP plays an important role in the corneal elasticity, and corneal elasticity change rate can increase the comparability of results between individuals.
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Affiliation(s)
- Sisi Chen
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zi Jin
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
- Department of Biomedical Engineering, College of Engineering, Peking University, Wenzhou, Beijing, China
| | - Gu Zheng
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Shuling Ye
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yiyi Wang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Weicheng Wang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yuanyuan Wang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Dexi Zhu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Meixiao Shen
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Fan Lu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
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Janknecht P. Is it Possible to Derive the Dresdner Correction Formula Using a Finite Element Program? Klin Monbl Augenheilkd 2021; 239:1262-1272. [PMID: 34243213 DOI: 10.1055/a-1478-3833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
INTRODUCTION The aim was to construct a model cornea by CAD and finite element software to find out how the intraocular pressure compares to the forces for applanation at the outside of the model cornea. These data were to be compared to the Dresdner correction formula. Thereby, it was possible to find out whether the model was plausible and to find hints as to why a correction for how the intraocular pressure depends on the corneal thickness is necessary at all. METHODS Using the open-source software FreeCad and geometrical data for the cornea of the literature, an average cornea was constructed. On this average cornea, a finite element analysis was performed using the free software z88aurora. The intraocular pressure was measured by applanation of the outer cornea. The necessary forces were analysed. RESULTS In this model, the intraocular pressure had to be corrected depending on the corneal thickness. The correction factor was kmean; finite elements = 19.17 - 0.0334*corneal thickness. The necessary correction did not exclusively depend on the relation between the endothelial area and the area of the outer cornea: for this relation alone the correction would have been karea-relation = 1.0361 - 0.0006*corneal thickness. DISCUSSION The model correction formula was close to the Dresdner formula. The relation between endothelial area and the area of the outer cornea could only explain about half of the necessary correction.
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Ma Y, Moroi SE, Roberts CJ. Non-invasive Clinical Measurement of Ocular Rigidity and Comparison to Biomechanical and Morphological Parameters in Glaucomatous and Healthy Subjects. Front Med (Lausanne) 2021; 8:701997. [PMID: 34291068 PMCID: PMC8287026 DOI: 10.3389/fmed.2021.701997] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/07/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose: To assess ocular rigidity using dynamic optical coherence tomography (OCT) videos in glaucomatous and healthy subjects, and to evaluate how ocular rigidity correlates with biomechanical and morphological characteristics of the human eye. Methods: Ocular rigidity was calculated using Friedenwald's empirical equation which estimates the change in intraocular pressure (IOP) produced by volumetric changes of the eye due to choroidal pulsations with each heartbeat. High-speed OCT video was utilized to non-invasively measure changes in choroidal volume through time-series analysis. A control-case study design was based on 23 healthy controls and 6 glaucoma cases. Multiple diagnostic modalities were performed during the same visit including Spectralis OCT for nerve head video, Pascal Dynamic Contour Tonometry for IOP and ocular pulse amplitude (OPA) measurement, Corvis ST for measuring dynamic biomechanical response, and Pentacam for morphological characterization. Results: Combining glaucoma and healthy cohorts (n = 29), there were negative correlations between ocular rigidity and axial length (Pearson R = −0.53, p = 0.003), and between ocular rigidity and anterior chamber volume (R = −0.64, p = 0.0002). There was a stronger positive correlation of ocular rigidity and scleral stiffness (i.e., stiffness parameter at the highest concavity [SP-HC]) (R = 0.62, p = 0.0005) compared to ocular rigidity and corneal stiffness (i.e., stiffness parameter at the first applanation [SP-A1]) (R = 0.41, p = 0.033). In addition, there was a positive correlation between ocular rigidity and the static pressure-volume ratio (P/V ratio) (R = 0.72, p < 0.0001). Conclusions: Ocular rigidity was non-invasively assessed using OCT video and OPA in a clinic setting. The significant correlation of ocular rigidity with biomechanical parameters, SP-HC and P/V ratio, demonstrated the validity of the ocular rigidity measurement. Ocular rigidity is driven to a greater extent by scleral stiffness than corneal stiffness. These in vivo methods offer an important approach to investigate the role of ocular biomechanics in glaucoma.
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Affiliation(s)
- Yanhui Ma
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, United States
| | - Sayoko E Moroi
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, United States
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
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Influence of the eye globe design on biomechanical analysis. Comput Biol Med 2021; 135:104612. [PMID: 34261005 DOI: 10.1016/j.compbiomed.2021.104612] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 06/11/2021] [Accepted: 06/23/2021] [Indexed: 11/21/2022]
Abstract
PURPOSE To assess the mechanical contribution of inner eye components on corneal deformation during a finite element analysis. METHODS A finite element model of an eye globe was implemented to examine the corneal response under various mechanical conditions. The model incorporates the cornea, limbus, sclera, iris, lens, muscles, anterior chamber and vitreous. The Ogden hyperelastic model was used for the corneo-limbal region and the Yeoh isotropic model for the sclera. The anterior chamber was modelled as a cavity and other eye components were incorporated as linear elastic material. A fluid dynamic simulation was implemented to determine the spatial air puff velocity and pressure profiles around corneal surface. RESULTS The maximal apical displacement under IOP = 15 mmHg was 0.22 mm with a stress of 0.013 MPa. An unrestrained limbus slightly increases the apical displacement, while an unrestrained equatorial sclera largely increases the displacement by 10%, resulting in reduced stiffness. The iris slightly decreases the displacement but increases stress in the corneal periphery. Meanwhile, the joint contribution of muscle and lens cannot be neglected as it reduces corneal displacement by 50%. Incorporation of the remaining eye components results in nearly similar results. Under air puff loading, a free equatorial sclera raised the dynamic deformation amplitude by nearly 2%, while the dynamic profile remained similar for all remaining study cases considered. CONCLUSION In a finite element analysis, the lens, iris, and muscle each provide major mechanical contributions to corneal deformation, and it is highly recommended that the internal contributions are considered.
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Scott JA, Roberts CJ, Mahmoud AM, Jain SG. Evaluating the Relationship of Intraocular Pressure and Anterior Chamber Volume With Use of Prostaglandin Analogues. J Glaucoma 2021; 30:421-427. [PMID: 33149104 DOI: 10.1097/ijg.0000000000001736] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/24/2020] [Indexed: 11/26/2022]
Abstract
PRCIS In this prospective study, naive prostaglandin use in primary open-angle glaucoma was associated with scleral biomechanical alteration and intraocular pressure (IOP) measuring errors. PURPOSE The purpose of this study is to determine the effects of naïve use of prostaglandin analogues (PGA) on IOP and anterior chamber volume (ACV), as well as investigate how PGAs might affect corneal and scleral stiffness and their impact on ocular rigidity. MATERIALS AND METHODS This study was a prospective study of 21 recently diagnosed open-angle glaucoma patients (33 eyes) initiating medical therapy with a topical prostaglandin eye drop. Corneal morphologic and biomechanical parameters as well as IOP were measured at 3 visits over a 4-month period with the following equipment: Pentacam, Corvis ST, Ocular Response Analyzer, Goldmann applanation tonometry (GAT) and Pascal dynamic contour tonometry. RESULTS The study demonstrated a significant decrease in mean IOP with initiation of PGA in all 4 tonometers (P<0.0001). The greatest change in IOP occurred in the first 4 weeks of treatment (P<0.0001). The mean ACV showed a significant decrease at visit 2 (P<0.02) and visit 3 (P<0.04) compared with baseline visit 1. However, there was a paradoxical increase in ACV in 37% of eyes at visit 2, despite a significant mean reduction in IOP by GAT and dynamic contour tonometry.The IOP/ACV ratio at visit 1 significantly predicted the reduction in respective measures of IOP, as well as scleral stiffness measured by stiffness parameter-highest concavity. CONCLUSION In clinical practice, GAT may not be the most appropriate tonometer for measuring IOP in PGA treated eyes due the measurement errors from ocular biomechanical alteration. The IOP/ACV ratio could potentially serve as a new diagnostic parameter to determine the likelihood of PGA treatment success.
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Affiliation(s)
| | - Cynthia J Roberts
- Departments of Ophthalmology & Vision Sciences
- Biomedical Engineering, Havener Eye Institute, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Ashraf M Mahmoud
- Departments of Ophthalmology & Vision Sciences
- Biomedical Engineering, Havener Eye Institute, The Ohio State University Wexner Medical Center, Columbus, OH
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Sedaghat MR, Momeni-Moghaddam H, Azimi A, Fakhimi Z, Ziaei M, Danesh Z, Roberts CJ, Monfared N, Jamali A. Corneal Biomechanical Properties in Varying Severities of Myopia. Front Bioeng Biotechnol 2021; 8:595330. [PMID: 33553113 PMCID: PMC7859342 DOI: 10.3389/fbioe.2020.595330] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 12/21/2020] [Indexed: 11/20/2022] Open
Abstract
Purpose: To investigate corneal biomechanical response parameters in varying degrees of myopia and their correlation with corneal geometrical parameters and axial length. Methods: In this prospective cross-sectional study, 172 eyes of 172 subjects, the severity degree of myopia was categorized into mild, moderate, severe, and extreme myopia. Cycloplegic refraction, corneal tomography using Pentacam HR, corneal biomechanical assessment using Corvis ST and Ocular Response Analyser (ORA), and ocular biometry using IOLMaster 700 were performed for all subjects. A general linear model was used to compare biomechanical parameters in various degrees of myopia, while central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered as covariates. Multiple linear regression was used to investigate the relationship between corneal biomechanical parameters with spherical equivalent (SE), axial length (AXL), bIOP, mean keratometry (Mean KR), and CCT. Results: Corneal biomechanical parameters assessed by Corvis ST that showed significant differences among the groups were second applanation length (AL2, p = 0.035), highest concavity radius (HCR, p < 0.001), deformation amplitude (DA, p < 0.001), peak distance (PD, p = 0.022), integrated inverse radius (IR, p < 0.001) and DA ratio (DAR, p = 0.004), while there were no significant differences in the means of pressure-derived parameters of ORA between groups. Multiple regression analysis showed all parameters of Corvis ST have significant relationships with level of myopia (SE, AXL, Mean KR), except AL1 and AL2. Significant biomechanical parameters showed progressive reduction in corneal stiffness with increasing myopia (either with greater negative SE or greater AXL), independent of IOP and CCT. Also, corneal hysteresis (CH) or ability to dissipate energy from the ORA decreased with increasing level of myopia. Conclusions: Dynamic corneal response assessed by Corvis ST shows evidence of biomechanical changes consistent with decreasing stiffness with increasing levels of myopia in multiple parameters. The strongest correlations were with highest concavity parameters where the sclera influence is maximal.
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Affiliation(s)
| | | | - Abbas Azimi
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.,Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Zohreh Fakhimi
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mohammed Ziaei
- Department of Ophthalmology, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Zeynad Danesh
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Cynthia J Roberts
- Ophthalmology & Visual Science, Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Naeemeh Monfared
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Alireza Jamali
- Department of Optometry, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran
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Mehr JA, Moss HE, Hatami-Marbini H. Numerical Investigation on the Role of Mechanical Factors Contributing to Globe Flattening in States of Elevated Intracranial Pressure. Life (Basel) 2020; 10:life10120316. [PMID: 33260780 PMCID: PMC7760332 DOI: 10.3390/life10120316] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 11/11/2020] [Accepted: 11/23/2020] [Indexed: 11/16/2022] Open
Abstract
Flattening of the posterior eye globe in the magnetic resonance (MR) images is a sign associated with elevated intracranial pressure (ICP), often seen in people with idiopathic intracranial hypertension (IIH). The exact underlying mechanisms of globe flattening (GF) are not fully known but mechanical factors are believed to play a role. In the present study, we investigated the effects of material properties and pressure loads on GF. For this purpose, we used a generic finite element model to investigate the deformation of the posterior eyeball. The degree of GF in numerical models and the significance of different mechanical factors on GF were characterized using an automated angle-slope technique and a statistical measure. From the numerical models, we found that ICP had the most important role in GF. We also showed that the angle-slope graphs pertaining to MR images from five people with high ICP can be represented numerically by manipulating the parameters of the finite element model. This numerical study suggests that GF observed in IIH patients can be accounted for by the forces caused by elevation of ICP from its normal level, while material properties of ocular tissues, such as sclera (SC), peripapillary sclera (PSC), and optic nerve (ON), would impact its severity.
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Affiliation(s)
- Jafar A. Mehr
- Computational Biomechanics Research Laboratory, Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL 60612, USA;
| | - Heather E. Moss
- Departments of Ophthalmology and Neurology & Neurosciences, Stanford University, Palo Alto, CA 94303, USA;
| | - Hamed Hatami-Marbini
- Computational Biomechanics Research Laboratory, Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL 60612, USA;
- Correspondence:
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Huang L, Shen M, Liu T, Zhang Y, Wang Y. Inverse solution of corneal material parameters based on non-contact tonometry: A comparative study of different constitutive models. J Biomech 2020; 112:110055. [PMID: 33039923 DOI: 10.1016/j.jbiomech.2020.110055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 08/15/2020] [Accepted: 09/17/2020] [Indexed: 11/16/2022]
Abstract
Assessing the biomechanical properties of the cornea in vivo is important for predicting the outcome of refractive surgery, and for controlling the risk of postoperative complications. In this study, we examined the impact of corneal mechanical properties (nonlinearity and anisotropy) on the inverse solution of corneal material parameters based on the non-contact tonometry ("air puff") test. Finite element models with different constitutive models (linear-elastic, isotropic hyperelastic, and fiber-dependent) were established to simulate the non-contact tonometry test. The results showed that the corneal nonlinear mechanical property and fiber distribution had significant effects on the corneal deflection profile. These findings may help in constructing an appropriate inverse solution strategy when using the inverse finite element method and in identifying individual differences in the corneal matrix shear modulus and fiber stiffness.
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Affiliation(s)
- Laixin Huang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China
| | - Min Shen
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China.
| | - Taiwei Liu
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China
| | - Yan Zhang
- Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Lab of Ophthalmology and Visual Science, Clinical College of Ophthalmology, Tianjin Medical University, Nankai University, Tianjin 300022, China
| | - Yan Wang
- Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Lab of Ophthalmology and Visual Science, Clinical College of Ophthalmology, Tianjin Medical University, Nankai University, Tianjin 300022, China
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Iglicki M, Zur D, Negri HP, Esteves J, Arias R, Holsman E, Loewenstein A, Busch C. Results in comparison between 30 gauge ultrathin wall and 27 gauge needle in sutureless intraocular lens flanged technique in diabetic patients: 24-month follow-up study. Acta Diabetol 2020; 57:1151-1157. [PMID: 32300875 DOI: 10.1007/s00592-020-01530-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 03/27/2020] [Indexed: 11/24/2022]
Abstract
AIMS Intraoperative complications in cataract surgery are more common in diabetic patients. Solving aphakia in these circumstances remains a challenge, as the scleral structure has been shown to be different in diabetes. This study aims to analyze the role of a secondary sutureless scleral intraocular lens (IOL) flanged fixation in diabetic patients without capsular support and to compare the anatomical and functional outcomes using a 30 gauge (G) ultrathin wall needle vs. a 27G needle. METHODS Retrospective, observational cohort study. 105 eyes (105 patients) who underwent PPV with secondary IOL fixation using a sutureless 27G (n = 51) or a 30G ultrathin wall (UTW) needle technique (n = 54) and had a 24 months postoperative follow up. Consecutive patients' records were reviewed for lens stability and centration parameters, intra- and postoperative complications at 7 days, 1, 3, 6, 12, and 24 months after surgery. Correlations between outcome measures and needle size (27G vs. 30G UTW) were analyzed. RESULTS IOL displacement occurred in 30 patients (41.2%) in the 27G group and did not occur in the 30G UTW needle group (p < 0.001). Mean time until IOL displacement was 10.5 ± 7.0 months (range: 7 days-24 months). IOL centricity was significantly better in the 30G ultrathin wall needle group compared to 27 G (p = 0.001). Additional surgical interventions were necessary only in the 27G group (n = 14). CONCLUSIONS Sutureless IOL flanged technique using a 30G UTW needle is more predictable and has less complications in aphakic diabetic patients, compared to a 27G needle technique.
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Affiliation(s)
- Matias Iglicki
- Retina Private Office, University of Buenos Aires, 525 Aguirre St., 3rd Floor, Apt. A, Buenos Aires, 1414, Argentina.
| | - Dinah Zur
- Ophthalmology Division, Tel Aviv Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | | | | | - Romina Arias
- Diagnostic Ophthalmology Center, Buenos Aires, Argentina
| | | | - Anat Loewenstein
- Ophthalmology Division, Tel Aviv Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Catharina Busch
- Ophthalmology Department, University of Leipzig, Leipzig, Germany
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Taroni L, Bernabei F, Pellegrini M, Roda M, Toschi PG, Mahmoud AM, Schiavi C, Giannaccare G, Roberts CJ. Corneal Biomechanical Response Alteration After Scleral Buckling Surgery for Rhegmatogenous Retinal Detachment. Am J Ophthalmol 2020; 217:49-54. [PMID: 32283097 DOI: 10.1016/j.ajo.2020.03.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/25/2020] [Accepted: 03/31/2020] [Indexed: 12/17/2022]
Abstract
PURPOSE To compare the corneal biomechanics of eyes that underwent scleral buckle (SB) for rhegmatogenous retinal detachment (RRD) with those of fellow eyes (fellow eyes) and to further investigate the effects of SB on intraocular pressure (IOP) values. DESIGN Retrospective, fellow-eye matched cohort study. METHODS A total of 18 consecutive patients (11 males and 7 females) treated with SB for RRD in 1 eye were enrolled. Goldmann applanation tonometry was used to measure IOP. Biomechanical properties of the cornea were investigated by using the Ocular Response Analyzer (ORA) (Reichert Instruments) for the calculation of corneal resistant factor (CRF), corneal hysteresis, Goldmann-correlated IOP, and corneal-compensated IOP. Customized software was used for analysis of the ORA infrared and pressure signals, and a significance threshold was set to a P value of .05. RESULTS Operated eyes (OEs) showed significantly lower values of corneal hysteresis and CRF than fellow eyes (9.0 ± 1.8 vs 10.1 ± 1.8 mm Hg, respectively; P < .001; 10.0 ± 2.2 vs 10.9 ± 2.2 mm Hg; P < .001). GAT was significantly lower than corneal-compensated IOP in OEs (18.1 ± 4.9 vs 19.8 ± 4.8 mm Hg, respectively; P = .022) but not in fellow eyes. The second applanation event (A2) took place earlier in time, and the cornea was moving faster during A2 in the OEs than in the fellow eyes. CONCLUSIONS SB for the treatment of RRD affects corneal biomechanical response, likely due to a less compliant sclera that limits corneal motion and reduces energy dissipation, reflected in a lower corneal hysteresis. This has potentially meaningful clinical implications as the accuracy of the measurement of IOP values may be affected in these eyes.
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Affiliation(s)
- Leonardo Taroni
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy.
| | - Federico Bernabei
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Marco Pellegrini
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Matilde Roda
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Pier Giorgio Toschi
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Ashraf M Mahmoud
- Department of Ophthalmology and Visual Science and Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Costantino Schiavi
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Giuseppe Giannaccare
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy; Department of Ophthalmology, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Science and Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
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De Stefano VS, Ford MR, Seven I, Dupps WJ. Depth-Dependent Corneal Biomechanical Properties in Normal and Keratoconic Subjects by Optical Coherence Elastography. Transl Vis Sci Technol 2020; 9:4. [PMID: 32832211 PMCID: PMC7414661 DOI: 10.1167/tvst.9.7.4] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 04/07/2020] [Indexed: 12/15/2022] Open
Abstract
Purpose Compare depth-resolved biomechanical properties in normal and keratoconic corneas in live human subjects using optical coherence elastography (OCE). Methods In a prospective series of normal and keratoconus (KC) eyes, a corneal perturbation was applied by a custom swept-source OCE system using a transparent flat lens coupled to force transducers. Cross-correlation was applied to track frame-by-frame OCT speckle displacement. Regional displacements for the anterior and posterior stroma were plotted in force versus displacement (k) graphs. A spatial biomechanical property ratio (ka/kp ) was defined by dividing the maximum total displacement by the maximum force for the anterior (ka ) and posterior cornea (kp) and was compared between normal and KC groups with the Mann-Whitney U test. Area under the receiver operating characteristics curve (AUROC) for differentiating normal and KC eyes was calculated for ka/kp , kmax, and thinnest point of corneal thickness (TPCT). Results Thirty-six eyes were analyzed (21 eyes of 12 normal subjects and 15 KC eyes of 12 subjects). The ka/kp for the normal group was 1.135 ± 0.07 (mean ± standard deviation) and 1.02 ± 0.08 for the KC group (P < 0.001), indicating a relative deficit in anterior stromal stiffness in KC eyes. AUROC was 0.91 for ka /kp , 0.95 for kmax, and 1 for TPCT. Conclusions Significant differences in depth-dependent corneal biomechanical properties were observed between normal and KC subjects. Translational Relevance OCE was applied for the first time to human KC subjects and revealed alterations in the normal anterior-to-posterior stromal stiffness gradient, a novel and clinically accessible disease biomarker.
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Affiliation(s)
- Vinicius S De Stefano
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA.,Department of Ophthalmology and Visual Sciences, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Matthew R Ford
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Ibrahim Seven
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - William J Dupps
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA.,Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA
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Kramer EG, Vincent SJ. Intraocular pressure changes in neophyte scleral lens wearers: A prospective study. Cont Lens Anterior Eye 2020; 43:609-612. [PMID: 32507406 DOI: 10.1016/j.clae.2020.05.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 05/15/2020] [Accepted: 05/20/2020] [Indexed: 12/19/2022]
Abstract
PURPOSE To examine the variation in intraocular pressure (IOP) during the first six months of scleral lens wear. METHODS Thirty-two neophyte scleral lens wearers were recruited and IOP was measured using Goldman applanation tonometry before, and after 1 and 6 months of scleral lens wear (following lens removal). All scleral lenses were designed based on scleral topography or an impression of the ocular surface. Central corneal thickness and the central post-lens fluid reservoir thickness were quantified using optical coherence tomography. RESULTS Post-lens removal IOP displayed an increasing trend after 1 and 6 months of lens wear, but the magnitude of change was not clinically or statistically significant using several repeated measures analyses to account for sporadic missing longitudinal data (mean increase of 1 mmHg or less, p > 0.05). Central corneal thickness and the central post-lens fluid reservoir remained stable throughout the first six months of lens wear. CONCLUSION IOP measured following lens removal did not vary significantly during the first 6 months of lens wear in scleral lens neophytes. Further research is required to determine if IOP varies during lens wear, following lens removal, or after longer-term lens wear due to suction forces or tissue compression beneath the landing zone.
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Affiliation(s)
| | - Stephen J Vincent
- Queensland University of Technology (QUT), Centre for Vision and Eye Research, School of Optometry and Vision Science, Contact Lens and Visual Optics Laboratory, Institute of Health and Biomedical Innovation, Queensland, Australia.
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Nguyen BA, Reilly MA, Roberts CJ. Biomechanical contribution of the sclera to dynamic corneal response in air-puff induced deformation in human donor eyes. Exp Eye Res 2019; 191:107904. [PMID: 31883460 DOI: 10.1016/j.exer.2019.107904] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 12/18/2019] [Accepted: 12/24/2019] [Indexed: 02/01/2023]
Abstract
This study was conducted to evaluate the impact of varying scleral material properties on the biomechanical response of the cornea under air-puff induced deformation. Twenty pairs of human donor eyes were obtained for this study. One eye from each pair had its sclera stiffened using 4% glutaraldehyde, while the fellow eye served as control for uniaxial strip testing. The whole globes were mounted in a rigid holder and intraocular pressure (IOP) was set using a saline column. Dynamic corneal response parameters were measured before and after scleral stiffening using the CorVis ST, a dynamic Scheimpflug analyzer. IOP was set to 10, 20, 30, and 40 mmHg, with at least 3 examinations performed at each pressure step. Uniaxial tensile testing data were fit to a neo-Hookean model to estimate the Young's modulus of treated and untreated sclera. Scleral Young's modulus was found to be significantly correlated with several response parameters, including Highest Concavity Deformation Amplitude, Peak Distance, Highest Concavity Radius, and Stiffness Parameter-Highest Concavity (SP-HC). There were significant increases in SP-HC after scleral stiffening at multiple levels of IOP, while no significant difference was observed in the corneal Stiffness Parameter - Applanation 1 (SP-A1) at any level of IOP. Scleral mechanical properties significantly influenced the corneal deformation response to an air-puff. The stiffer the sclera, the greater the constraining effect on corneal deformation resulting in lower displaced amplitude. This may have important clinical implications and suggests that both corneal and scleral material properties contribute to the observed corneal response in air-puff induced deformation.
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Affiliation(s)
- B Audrey Nguyen
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology & Visual Science, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite, 5000, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology & Visual Science, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite, 5000, The Ohio State University, Columbus, OH, USA.
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Maklad O, Eliasy A, Chen KJ, Theofilis V, Elsheikh A. Simulation of Air Puff Tonometry Test Using Arbitrary Lagrangian-Eulerian (ALE) Deforming Mesh for Corneal Material Characterisation. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 17:E54. [PMID: 31861736 PMCID: PMC6982245 DOI: 10.3390/ijerph17010054] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 12/09/2019] [Accepted: 12/18/2019] [Indexed: 01/23/2023]
Abstract
: Purpose: To improve numerical simulation of the non-contact tonometry test by using arbitrary Lagrangian-Eulerian deforming mesh in the coupling between computational fluid dynamics model of an air jet and finite element model of the human eye. METHODS Computational fluid dynamics model simulated impingement of the air puff and employed Spallart-Allmaras model to capture turbulence of the air jet. The time span of the jet was 30 ms and maximum Reynolds number was Re=2.3×104, with jet orifice diameter 2.4 mm and impinging distance 11 mm. The model of the human eye was analysed using finite element method with regional hyperelastic material variation and corneal patient-specific topography starting from stress-free configuration. The cornea was free to deform as a response to the air puff using an adaptive deforming mesh at every time step of the solution. Aqueous and vitreous humours were simulated as a fluid cavity filled with incompressible fluid with a density of 1000 kg/m3. RESULTS Using the adaptive deforming mesh in numerical simulation of the air puff test improved the traditional understanding of how pressure distribution on cornea changes with time of the test. There was a mean decrease in maximum pressure (at corneal apex) of 6.29 ± 2.2% and a development of negative pressure on a peripheral corneal region 2-4 mm away from cornea centre. CONCLUSIONS The study presented an improvement of numerical simulation of the air puff test, which will lead to more accurate intraocular pressure (IOP) and corneal material behaviour estimation. The parametric study showed that pressure of the air puff is different from one model to another, value-wise and distribution-wise, based on cornea biomechanical parameters.
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Affiliation(s)
- Osama Maklad
- School of Engineering, University of Liverpool, Liverpool L69 3GH, UK
| | - Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool L69 3GH, UK
| | - Kai-Jung Chen
- School of Engineering, University of Liverpool, Liverpool L69 3GH, UK
| | | | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool L69 3GH, UK
- NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London EC1V 9EL, UK
- School of Biological Science and Biomedical Engineering, Beihang University, Beijing 100191, China
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Serbecic N, Beutelspacher S, Markovic L, Roy AS, Shetty R. Repeatability and reproducibility of corneal biomechanical parameters derived from Corvis ST. Eur J Ophthalmol 2019; 30:1287-1294. [PMID: 31744320 DOI: 10.1177/1120672119864554] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
INTRODUCTION The aim of this study was to evaluate repeatability and reproducibility of newly calculated biomechanical parameters of the cornea, developed by our research group. METHODS One eye from each of the 23 healthy subjects was measured three times consecutively, three times at different daytimes and on three different days. The within-subject standard deviation and coefficient of variation, as well as the intraclass correlation coefficient, were calculated for every parameter in each group. RESULTS Excellent repeatability and reproducibility (coefficient of variation < 5%, intraclass correlation coefficient > 0.75) was found for corrected values measured at A1, HC, and A2 time points (2nd A2 Time, 2nd A1 Time, 2nd HC Time, 2nd HC Def Amp and 2nd A1 Def Amp). Corneal-specific stiffness parameters, which showed good repeatability and reliability, were DA_cor (coefficient of variation = 4.02%, intraclass correlation coefficient = 0.919), KcLinear (coefficient of variation = 4.03%, intraclass correlation coefficient = 0.895), areaForceCornea (coefficient of variation = 3.34%, intraclass correlation coefficient = 0.853) and E2 (coefficient of variation = 4.1%, intraclass correlation coefficient = 0.78). Overall, most parameters fell into the category of good reliability (high intraclass correlation coefficient) and poor reproducibility (low coefficient of variation), including all the parameters describing extraocular deformation (DA_ext, AEPvED, AUC EDef, areaForceExtra, Kg and μg). Comparing the coefficient of variation values for intrasession, intersession and daytime measurements, there were no indices for diurnal changes. CONCLUSION Most parameters showed good repeatability and reliability. The extraocular stiffness parameters showed poor reproducibility. KcLinear can serve as a very reliable and repeatable indicator of corneal stiffness.
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Affiliation(s)
- Nermin Serbecic
- Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
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Francis M, Matalia H, Nuijts RMMA, Haex B, Shetty R, Sinha Roy A. Corneal Viscous Properties Cannot Be Determined From Air-Puff Applanation. J Refract Surg 2019; 35:730-736. [PMID: 31710375 DOI: 10.3928/1081597x-20191010-03] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 10/10/2019] [Indexed: 11/20/2022]
Abstract
PURPOSE To assess whether corneal viscous properties are measureable with air-puff applanation in patients. METHODS The study had 312 normal eyes, 107 fellow eyes of patients with keratoconus, and 289 keratoconic eyes. The Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) deformation data for all eyes were analyzed using two models. First, a standard linear solid model (SLM) assumed the cornea was an elastic material only. Second, a two-compartment Kelvin-Voigt model (KVM) assumed the cornea was a visco-elastic material. Corneal stiffness and viscosity were calculated. Further, the deflection amplitude was phase shifted virtually relative to the air-puff applanation force to assess whether the KVM was capable of detecting corneal viscous properties from air-puff applanation. This was similar in concept to measured viscoelastic deformations in other soft tissues. The hysteresis area was also calculated with deformation (cornea and whole globe) and deflection (cornea only) amplitude. The greater the magnitude of the hysteresis area, the greater was the magnitude of corneal viscosity (µc). RESULTS Both the SLM and KVM reported similar magnitudes of corneal stiffnesses (correlation coefficient > 0.99). However, for a given model, corneal stiffness was significantly different between normal, fellow, and keratoconic eyes (P = .001). From the KVM, the corneal viscosity was different between groups (P = .001) but was small in magnitude (order of 10-9). The deflection hysteresis area was also small in magnitude (order of 10-6). In contrast, the KVM detected significant corneal viscosity only when the deflection amplitude was virtually phase shifted with respect to the air-puff applanation force. CONCLUSIONS No significant corneal viscous response was detected in patients who had air-puff applanation. [J Refract Surg. 2019;35(11):730-736.].
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