1
|
Gong Z, Bojikian KD, Chen A, Chen PP, Rezaei KA, Olmos LC, Mudumbai RC, Li J, Schwartz DM, Wang RK. In-vivo characterization of scleral rigidity in myopic eyes using fundus-pulsation optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2024; 15:3426-3440. [PMID: 38855699 PMCID: PMC11161338 DOI: 10.1364/boe.523835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 04/19/2024] [Accepted: 04/21/2024] [Indexed: 06/11/2024]
Abstract
The sclera plays an important role in the structural integrity of the eye. However, as myopia progresses, the elongation of the eyeball exerts stretching forces on the posterior sclera, which typically happens in conjunction with scleral remodeling that causes rigidity loss. These biomechanical alterations can cause localized eyeball deformation and vision impairment. Therefore, monitoring scleral rigidity is clinically important for the management and risk assessment of myopia. In this study, we propose fundus pulsation optical coherence elastography (FP-OCE) to characterize posterior scleral rigidity in living humans. This methodology is based on a choroidal pulsation model, where the scleral rigidity is inversely associated with the choroidal max strain obtained through phase-sensitive optical coherence tomography (PhS-OCT) measurement of choroidal deformation and thickness. Using FP-OCE, we conducted a pilot clinical study to explore the relationship between choroidal strain and myopia severity. The results revealed a significant increase in choroidal max strain in pathologic myopia, indicating a critical threshold beyond which scleral rigidity decreases significantly. Our findings offer a potential new method for monitoring myopia progression and evaluating therapies that alter scleral mechanical properties.
Collapse
Affiliation(s)
- Zhaoyu Gong
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | | | - Andrew Chen
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Philip P. Chen
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Kasra A. Rezaei
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Lisa C. Olmos
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Raghu C. Mudumbai
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Jonathan Li
- Department of Ophthalmology, University of California, San Francisco, CA, USA
| | - Daniel M. Schwartz
- Department of Ophthalmology, University of California, San Francisco, CA, USA
- Merkin Institute for Translational Research, California Institute of Technology, Pasadena, CA 91125, USA
| | - Ruikang K. Wang
- Department of Bioengineering, University of Washington, Seattle, WA, USA
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| |
Collapse
|
2
|
Li GY, Feng X, Yun SH. Simultaneous tensile and shear measurement of the human cornea in vivo using S0- and A0-wave optical coherence elastography. Acta Biomater 2024; 175:114-122. [PMID: 38101555 PMCID: PMC10872441 DOI: 10.1016/j.actbio.2023.12.019] [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: 08/09/2023] [Revised: 11/09/2023] [Accepted: 12/08/2023] [Indexed: 12/17/2023]
Abstract
Understanding corneal stiffness is valuable for improving refractive surgery, detecting corneal abnormalities, and assessing intraocular pressure. However, accurately measuring the elastic properties, specifically the tensile and shear moduli that govern mechanical deformation, has been challenging. To tackle this issue, we have developed guided-wave optical coherence elastography that can simultaneously excite and analyze symmetric (S0) and anti-symmetric (A0) elastic waves in the cornea at around 10 kHz frequencies, enabling us to extract tensile and shear properties from measured wave dispersion curves. We verified the technique using elastomer phantoms and ex vivo porcine corneas and investigated the dependence on intraocular pressure using acoustoelastic theory that incorporates corneal tension and a nonlinear constitutive tissue model. In a pilot study involving six healthy human subjects aged 31 to 62, we measured shear moduli (Gzx) of 94±20 kPa (mean±standard deviation) and tensile moduli (Exx) of 4.0±1.1 MPa at central corneas. Our preliminary analysis of age-dependence revealed contrasting trends: -8.3±4.5 kPa/decade for shear and 0.30±0.21 MPa/decade for tensile modulus. This OCE technique has the potential to become a highly useful clinical tool for the quantitative biomechanical assessment of the cornea. STATEMENT OF SIGNIFICANCE: This article reports an innovative elastography technique using two guided elastic waves, demonstrating the measurement of both tensile and shear moduli in human cornea in vivo with unprecedented precision. This technique paves the way for comprehensive investigations into corneal mechanics and holds clinical significance in various aspects of corneal health and disease management.
Collapse
Affiliation(s)
- Guo-Yang Li
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom St., Boston, MA 02114, USA
| | - Xu Feng
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom St., Boston, MA 02114, USA
| | - Seok-Hyun Yun
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom St., Boston, MA 02114, USA; Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139, USA.
| |
Collapse
|
3
|
Miao YY, Ma XM, Qu ZX, Eliasy A, Wu BW, Xu H, Wang P, Zheng XB, Wang JJ, Ye YF, Chen SH, Elsheikh A, Bao FJ. Performance of Corvis ST Parameters Including Updated Stress-Strain Index in Differentiating Between Normal, Forme-Fruste, Subclinical, and Clinical Keratoconic Eyes. Am J Ophthalmol 2024; 258:196-207. [PMID: 37879454 DOI: 10.1016/j.ajo.2023.10.015] [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: 05/31/2023] [Revised: 10/18/2023] [Accepted: 10/20/2023] [Indexed: 10/27/2023]
Abstract
PURPOSE This study seeks to evaluate the ability of the updated stress strain index (SSIv2) and other Corvis ST biomechanical parameters in distinguishing between keratoconus at different disease stages and normal eyes. DESIGN Diagnostic accuracy analysis to distinguish disease stages. METHODS 1084 eyes were included and divided into groups of normal (199 eyes), forme fruste keratoconus (FFKC, 194 eyes), subclinical keratoconus (SKC, 113 eyes), mild clinical keratoconus (CKC-Ⅰ, 175 eyes), moderate clinical keratoconus (CKC-Ⅱ, 204 eyes), and severe clinical keratoconus (CKC-Ⅲ, 199 eyes). Each eye was subjected to a Corvis ST examination to determine the central corneal thickness (CCT), biomechanically corrected intraocular pressure (bIOP), SSIv2 (updated stress-strain index), and other 8 Corvis parameters including the stress-strain index (SSIv1), stiffness parameter at first applanation (SP-A1), first applanation time (A1T), Ambrósio relational thickness to the horizontal profile (ARTh), integrated inverse radius (IIR), maximum deformation amplitude (DAM), ratio between deformation amplitude at the apex and at 2 mm nasal and temporal (DARatio2), and Corvis biomechanical index (CBI). The sensitivity and specificity of these parameters in diagnosing keratoconus were analyzed through receiver operating characteristic curves. RESULTS Before and after correction for CCT and bIOP, SSIv2 and ARTh were significantly higher and IIR and CBI were significantly lower in the normal group than in the FFKC group, SKC group and the 3 CKC groups (all P < .05). There were also significant correlations between the values of SSIv2, ARTh, IIR, CBI, and the CKC severity (all P < .05). AUC of SSIv2 was significantly higher than all other Corvis parameters in distinguishing normal eyes from FFKC, followed by IIR, ARTh and CBI. CONCLUSION Corvis ST's updated stress-strain index, SSIv2, demonstrated superior performance in differentiating between normal and keratoconic corneas, and between corneas with different keratoconus stages. Similar, but less pronounced, performance was demonstrated by the IIR, ARTh and CBI.
Collapse
Affiliation(s)
- Yuan-Yuan Miao
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China
| | - Xiao-Min Ma
- Shanghai Eighth People's Hospital (X.-M.M.), Shanghai, China
| | - Zhan-Xin Qu
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China
| | - Ashkan Eliasy
- School of Engineering, University of Liverpool (A.Eli., A.Els.), Liverpool, United Kingdom
| | - Bo-Wen Wu
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China
| | - Hui Xu
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China
| | - Pu Wang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China
| | - Xiao-Bo Zheng
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China; The Institute of Ocular Biomechanics, Wenzhou Medical University (X.-B.Z., J.-J.W., S.-H.C., F.-J.B.), Wenzhou, Zhejiang, China
| | - Jun-Jie Wang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China; The Institute of Ocular Biomechanics, Wenzhou Medical University (X.-B.Z., J.-J.W., S.-H.C., F.-J.B.), Wenzhou, Zhejiang, China
| | - Yu-Feng Ye
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China
| | - Shi-Hao Chen
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China; The Institute of Ocular Biomechanics, Wenzhou Medical University (X.-B.Z., J.-J.W., S.-H.C., F.-J.B.), Wenzhou, Zhejiang, China.
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool (A.Eli., A.Els.), Liverpool, United Kingdom; National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology (A.Els.), London, United Kingdom; Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University (A.Els.), Beijing, China
| | - Fang-Jun Bao
- National Clinical Research Center for Ocular Diseases, Eye Hospital, WenZhou Medical University (Y.-Y.M., Z.-X.Q., B.-W.W., H.X., P.W., X.-B.Z., J.-J.W., Y.-F.Y., S.-H.C., F.-J.B), Wenzhou, Zhejiang, China; The Institute of Ocular Biomechanics, Wenzhou Medical University (X.-B.Z., J.-J.W., S.-H.C., F.-J.B.), Wenzhou, Zhejiang, China.
| |
Collapse
|
4
|
Nair A, Zvietcovich F, Singh M, Weikert MP, Aglyamov SR, Larin KV. Optical coherence elastography measures the biomechanical properties of the ex vivo porcine cornea after LASIK. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:016002. [PMID: 38223300 PMCID: PMC10787573 DOI: 10.1117/1.jbo.29.1.016002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 11/29/2023] [Accepted: 12/26/2023] [Indexed: 01/16/2024]
Abstract
Significance The biomechanical impact of refractive surgery has long been an area of investigation. Changes to the cornea structure cause alterations to its mechanical integrity, but few studies have examined its specific mechanical impact. Aim To quantify how the biomechanical properties of the cornea are altered by laser assisted in situ keratomileusis (LASIK) using optical coherence elastography (OCE) in ex vivo porcine corneas. Approach Three OCE techniques, wave-based air-coupled ultrasound (ACUS) OCE, heartbeat (Hb) OCE, and compression OCE were used to measure the mechanical properties of paired porcine corneas, where one eye of the pair was left untreated, and the fellow eye underwent LASIK. Changes in stiffness as a function of intraocular pressure (IOP) before and after LASIK were measured using each technique. Results ACUS-OCE showed that corneal stiffness changed as a function of IOP for both the untreated and the treated groups. The elastic wave speed after LASIK was lower than before LASIK. Hb-OCE and compression OCE showed regional changes in corneal strain after LASIK, where the absolute strain difference between the cornea anterior and posterior increased after LASIK. Conclusions The results of this study suggest that LASIK may soften the cornea and that these changes are largely localized to the region where the surgery was performed.
Collapse
Affiliation(s)
- Achuth Nair
- University of Houston, Department of Biomedical Engineering, Houston, Texas, United States
| | | | - Manmohan Singh
- University of Houston, Department of Biomedical Engineering, Houston, Texas, United States
| | - Mitchell P. Weikert
- Baylor College of Medicine, Cullen Eye Institute, Houston, Texas, United States
| | - Salavat R. Aglyamov
- University of Houston, Department of Mechanical Engineering, Houston, Texas, United States
| | - Kirill V. Larin
- University of Houston, Department of Biomedical Engineering, Houston, Texas, United States
- Baylor College of Medicine, Department of Physiology and Biophysics, Houston, Texas, United States
| |
Collapse
|
5
|
Frigelli M, Büchler P, Kling S. Optomechanical assessment of photorefractive corneal cross-linking via optical coherence elastography. Front Bioeng Biotechnol 2023; 11:1272097. [PMID: 38026898 PMCID: PMC10680454 DOI: 10.3389/fbioe.2023.1272097] [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: 08/03/2023] [Accepted: 10/20/2023] [Indexed: 12/01/2023] Open
Abstract
Purpose: Corneal cross-linking (CXL) has recently been used with promising results to positively affect corneal refractive power in the treatment of hyperopia and mild myopia. However, understanding and predicting the optomechanical changes induced by this procedure are challenging. Methods: We applied ambient pressure modulation based optical coherence elastography (OCE) to quantify the refractive and mechanical effects of patterned CXL and their relationship to energy delivered during the treatment on porcine corneas. Three different patterned treatments were performed, designed according to Zernike polynomial functions (circle, astigmatism, coma). In addition, three different irradiation protocols were analyzed: standard Dresden CXL (fluence of 5.4 J/cm2), accelerated CXL (fluence of 5.4 J/cm2), and high-fluence CXL (fluence of 16.2 J/cm2). The axial strain distribution in the stroma induced by ocular inflation (Δp = 30 mmHg) was quantified, maps of the anterior sagittal curvature were constructed and cylindrical refraction was assessed. Results: Thirty minutes after CXL, there was a statistically significant increase in axial strain amplitude (p < 0.050) and a reduction in sagittal curvature (p < 0.050) in the regions treated with all irradiation patterns compared to the non-irradiated ones. Thirty-6 hours later, the non-irradiated regions showed compressive strains, while the axial strain in the CXL-treated regions was close to zero, and the reduction in sagittal curvature observed 30 minutes after the treatment was maintained. The Dresden CXL and accelerated CXL produced comparable amounts of stiffening and refractive changes (p = 0.856), while high-fluence CXL produced the strongest response in terms of axial strain (6.9‰ ± 1.9‰) and refractive correction (3.4 ± 0.9 D). Tripling the energy administered during CXL resulted in a 2.4-fold increase in the resulting refractive correction. Conclusion: OCE showed that refractive changes and alterations in corneal biomechanics are directly related. A patient-specific selection of both, the administered UV fluence and the irradiation pattern during CXL is promising to allow customized photorefractive corrections in the future.
Collapse
Affiliation(s)
- Matteo Frigelli
- Computational Bioengineering Group, ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Philippe Büchler
- Computational Bioengineering Group, ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Sabine Kling
- Computational Bioengineering Group, ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
- Institute for Biomedical Engineering, ITET Department, ETH Zürich, Zürich, Switzerland
| |
Collapse
|
6
|
Latus S, Grube S, Eixmann T, Neidhardt M, Gerlach S, Mieling R, Huttmann G, Lutz M, Schlaefer A. A Miniature Dual-Fiber Probe for Quantitative Optical Coherence Elastography. IEEE Trans Biomed Eng 2023; 70:3064-3072. [PMID: 37167045 DOI: 10.1109/tbme.2023.3275539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
OBJECTIVE Optical coherence elastography (OCE) allows for high resolution analysis of elastic tissue properties. However, due to the limited penetration of light into tissue, miniature probes are required to reach structures inside the body, e.g., vessel walls. Shear wave elastography relates shear wave velocities to quantitative estimates of elasticity. Generally, this is achieved by measuring the runtime of waves between two or multiple points. For miniature probes, optical fibers have been integrated and the runtime between the point of excitation and a single measurement point has been considered. This approach requires precise temporal synchronization and spatial calibration between excitation and imaging. METHODS We present a miniaturized dual-fiber OCE probe of 1 mm diameter allowing for robust shear wave elastography. Shear wave velocity is estimated between two optics and hence independent of wave propagation between excitation and imaging. We quantify the wave propagation by evaluating either a single or two measurement points. Particularly, we compare both approaches to ultrasound elastography. RESULTS Our experimental results demonstrate that quantification of local tissue elasticities is feasible. For homogeneous soft tissue phantoms, we obtain mean deviations of 0.15 ms-1 and 0.02 ms-1 for single-fiber and dual-fiber OCE, respectively. In inhomogeneous phantoms, we measure mean deviations of up to 0.54 ms-1 and 0.03 ms-1 for single-fiber and dual-fiber OCE, respectively. CONCLUSION We present a dual-fiber OCE approach that is much more robust in inhomogeneous tissues. Moreover, we demonstrate the feasibility of elasticity quantification in ex-vivo coronary arteries. SIGNIFICANCE This study introduces an approach for robust elasticity quantification from within the tissue.
Collapse
|
7
|
Zhu Y, Shi J, Alvarez-Arenas TEG, Li C, Wang H, Zhang D, He X, Wu X. Noncontact longitudinal shear wave imaging for the evaluation of heterogeneous porcine brain biomechanical properties using optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2023; 14:5113-5126. [PMID: 37854580 PMCID: PMC10581781 DOI: 10.1364/boe.497801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 08/09/2023] [Accepted: 08/09/2023] [Indexed: 10/20/2023]
Abstract
High-resolution quantification of heterogeneous brain biomechanical properties has long been an important topic. Longitudinal shear waves (LSWs) can be used to assess the longitudinal Young's modulus, but contact excitation methods have been used in most previous studies. We propose an air-coupled ultrasound transducer-based optical coherence elastography (AcUT-OCE) technique for noncontact excitation and detection of LSWs in samples and assessment of the nonuniformity of the brain's biomechanical properties. The air-coupled ultrasonic transducer (AcUT) for noncontact excitation of LSWs in the sample has a center frequency of 250 kHz. Phase-resolved Doppler optical coherence tomography (OCT) was used to image and reconstruct the propagation behavior of LSWs and surface ultrasound waves at high resolution. An agar phantom model was used to verify the feasibility of the experimental protocol, and experiments with ex vivo porcine brain samples were used to assess the nonuniformity of the brain biomechanical properties. LSWs with velocities of 0.83 ± 0.11 m/s were successfully excited in the agar phantom model. The perivascular elastography results in the prefrontal cortex (PFC) of the ex vivo porcine brains showed that the Young's modulus was significantly higher in the longitudinal and transverse directions on the left side of the cerebral vessels than on the right side and that the Young's modulus of the PFC decreased with increasing depth. The AcUT-OCE technique, as a new scheme for LSW applications in in vivo elastography, can be used for noncontact excitation of LSWs in brain tissue and high-resolution detection of heterogeneous brain biomechanical properties.
Collapse
Affiliation(s)
- Yirui Zhu
- School of Physics, Nanjing University, Nanjing, 210093, China
- School of Testing and Opto-electric Engineering, Nanchang Hangkong University, Nanchang, 330063, China
| | - Jiulin Shi
- School of Testing and Opto-electric Engineering, Nanchang Hangkong University, Nanchang, 330063, China
| | - Tomas E Gomez Alvarez-Arenas
- Ultrasonic and Sensors Technologies Department, Information and Physical Technologies Institute, Spanish National Research Council, Serrano 144, 28006, Madrid, Spain
| | - Chenxi Li
- School of Testing and Opto-electric Engineering, Nanchang Hangkong University, Nanchang, 330063, China
| | - Haohao Wang
- School of Testing and Opto-electric Engineering, Nanchang Hangkong University, Nanchang, 330063, China
| | - Dong Zhang
- School of Physics, Nanjing University, Nanjing, 210093, China
| | - Xingdao He
- School of Testing and Opto-electric Engineering, Nanchang Hangkong University, Nanchang, 330063, China
| | - Xiao Wu
- School of Physics, Nanjing University, Nanjing, 210093, China
| |
Collapse
|
8
|
Li GY, Feng X, Yun SH. Simultaneous tensile and shear measurement of the human cornea in vivo using S0- and A0-wave optical coherence elastography. ARXIV 2023:arXiv:2308.05316v1. [PMID: 37608935 PMCID: PMC10441437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Figures] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Understanding corneal stiffness is valuable for improving refractive surgery, detecting corneal abnormalities, and assessing intraocular pressure. However, accurately measuring the elastic properties, particularly the tensile and shear moduli that govern mechanical deformation, has been challenging. To tackle this issue, we have developed guided-wave optical coherence elastography that can simultaneously excite and analyze symmetric (S0) and anti-symmetric (A0) elastic waves in the cornea at frequencies around 10 kHz and allows us to extract tensile and shear properties from measured wave dispersion curves. By applying acoustoelastic theory that incorporates corneal tension and a nonlinear constitutive tissue model, we verified the technique using elastomer phantoms and ex vivo porcine corneas and investigated the dependence on intraocular pressure. For two healthy human subjects, we measured a mean tensile modulus of 3.6 MPa and a mean shear modulus of 76 kPa in vivo with estimated errors of < 4%. This technique shows promise for the quantitative biomechanical assessment of the cornea in a clinical setting.
Collapse
Affiliation(s)
- Guo-Yang Li
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom St., Boston, MA 02114, USA
| | - Xu Feng
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom St., Boston, MA 02114, USA
| | - Seok-Hyun Yun
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom St., Boston, MA 02114, USA
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139, USA
| |
Collapse
|
9
|
Zhu Y, Zhao Y, Shi J, Gomez Alvarez-Arenas TE, Yang H, Cai H, Zhang D, He X, Wu X. Novel acoustic radiation force optical coherence elastography based on ultrasmall ultrasound transducer for biomechanics evaluation of in vivo cornea. JOURNAL OF BIOPHOTONICS 2023:e202300074. [PMID: 37101410 DOI: 10.1002/jbio.202300074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/09/2023] [Accepted: 04/25/2023] [Indexed: 05/23/2023]
Abstract
We developed a novel acoustic radiation force optical coherence elastography (ARF-OCE) based on an ultrasmall ultrasound transducer for quantitative biomechanics evaluations of in vivo cornea. A custom single-sided meta-ultrasonic transducer with an outer diameter of 1.8 mm, focal spot diameter of 1.6 mm, central frequency of 930 kHz, and focal length of 0.8 mm was applied to excite the sample. The sample arm of the ARF-OCE system employed a three-dimensional printed holder that allowed for ultrasound excitation and ARF-OCE detection. The phase-resolved algorithm was combined with a Lamb wave model to depth-resolved evaluate corneal biomechanics after keratoconus and cross-linking treatments (CXL). The results showed that, compare to the healthy cornea, the Lamb wave velocity was significantly reduced in the keratoconus, increased in the cornea after CXL, and increased with cross-linked irradiation energy in the cornea. These results indicated the good clinical translation potential of the proposed novel ARF-OCE.
Collapse
Affiliation(s)
- Yirui Zhu
- School of Physics, Nanjing University, Nanjing, China
- School of Testing and Opto-Electric Engineering, Nanchang Hangkong University, Nanchang, China
| | - Yanzhi Zhao
- School of Medicine, Nanchang University, Nanchang, China
| | - Jiulin Shi
- School of Testing and Opto-Electric Engineering, Nanchang Hangkong University, Nanchang, China
| | - Tomas E Gomez Alvarez-Arenas
- Ultrasonic and Sensors Technologies Department, Information and Physical Technologies Institute, Spanish National Research Council, Madrid, Spain
| | - Hongwei Yang
- School of Medicine, Nanchang University, Nanchang, China
| | - Hongling Cai
- School of Physics, Nanjing University, Nanjing, China
| | - Dong Zhang
- School of Physics, Nanjing University, Nanjing, China
| | - Xingdao He
- School of Testing and Opto-Electric Engineering, Nanchang Hangkong University, Nanchang, China
| | - Xiaoshan Wu
- School of Physics, Nanjing University, Nanjing, China
| |
Collapse
|
10
|
Lan G, Twa MD, Song C, Feng J, Huang Y, Xu J, Qin J, An L, Wei X. In vivo corneal elastography: A topical review of challenges and opportunities. Comput Struct Biotechnol J 2023; 21:2664-2687. [PMID: 37181662 PMCID: PMC10173410 DOI: 10.1016/j.csbj.2023.04.009] [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: 02/14/2023] [Revised: 04/07/2023] [Accepted: 04/12/2023] [Indexed: 05/16/2023] Open
Abstract
Clinical measurement of corneal biomechanics can aid in the early diagnosis, progression tracking, and treatment evaluation of ocular diseases. Over the past two decades, interdisciplinary collaborations between investigators in optical engineering, analytical biomechanical modeling, and clinical research has expanded our knowledge of corneal biomechanics. These advances have led to innovations in testing methods (ex vivo, and recently, in vivo) across multiple spatial and strain scales. However, in vivo measurement of corneal biomechanics remains a long-standing challenge and is currently an active area of research. Here, we review the existing and emerging approaches for in vivo corneal biomechanics evaluation, which include corneal applanation methods, such as ocular response analyzer (ORA) and corneal visualization Scheimpflug technology (Corvis ST), Brillouin microscopy, and elastography methods, and the emerging field of optical coherence elastography (OCE). We describe the fundamental concepts, analytical methods, and current clinical status for each of these methods. Finally, we discuss open questions for the current state of in vivo biomechanics assessment techniques and requirements for wider use that will further broaden our understanding of corneal biomechanics for the detection and management of ocular diseases, and improve the safety and efficacy of future clinical practice.
Collapse
Affiliation(s)
- Gongpu Lan
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Michael D Twa
- College of Optometry, University of Houston, Houston, TX 77204, United States
| | - Chengjin Song
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
| | - JinPing Feng
- Institute of Engineering and Technology, Hubei University of Science and Technology, Xianning, Hubei 437100, China
| | - Yanping Huang
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jingjiang Xu
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jia Qin
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Lin An
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Xunbin Wei
- Biomedical Engineering Department, Peking University, Beijing 100081, China
- International Cancer Institute, Peking University, Beijing 100191, China
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| |
Collapse
|
11
|
Kirby MA, Regnault G, Pelivanov I, O'Donnell M, Wang RK, Shen TT. Noncontact Acoustic Micro-Tapping Optical Coherence Elastography for Quantification of Corneal Anisotropic Elasticity: In Vivo Rabbit Study. Transl Vis Sci Technol 2023; 12:15. [PMID: 36930138 PMCID: PMC10036949 DOI: 10.1167/tvst.12.3.15] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023] Open
Abstract
Purpose The purpose of this study was to demonstrate accurate measurement of corneal elastic moduli in vivo with noncontact and noninvasive optical coherence elastography. Methods Elastic properties (in-plane Young's modulus, E, and both in-plane, μ, and out-of-plane, G, shear moduli) of rabbit cornea were quantified in vivo using noncontact dynamic acoustic micro-tapping optical coherence elastography (AµT-OCE). The intraocular pressure (IOP)-dependence of measured mechanical properties was explored in extracted whole globes following in vivo measurement. A nearly incompressible transverse isotropic (NITI) model was used to reconstruct moduli from AµT-OCE data. Independently, cornea elastic moduli were also measured ex vivo with traditional, destructive mechanical tests (tensile extensometry and shear rheometry). Results Our study demonstrates strong anisotropy of corneal elasticity in rabbits. The in-plane Young's modulus, computed as E = 3μ, was in the range of 20 MPa to 44 MPa, whereas the out-of-plane shear modulus was in the range of 34 kPa to 261 kPa. Both pressure-dependent ex vivo OCE and destructive mechanical tests performed on the same samples within an hour of euthanasia strongly support the results of AµT-OCE measurements. Conclusions Noncontact AµT-OCE can noninvasively quantify cornea anisotropic elastic properties in vivo. Translational Relevance As optical coherence tomography (OCT) is broadly accepted in ophthalmology, these results suggest the potential for rapid translation of AµT-OCE into clinical practice. In addition, AµT-OCE can likely improve diagnostic criteria of ectatic corneal diseases, leading to early diagnosis, reduced complications, customized surgical treatment, and personalized biomechanical models of the eye.
Collapse
Affiliation(s)
- Mitchell A Kirby
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Gabriel Regnault
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Ivan Pelivanov
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Matthew O'Donnell
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Ruikang K Wang
- Department of Bioengineering, University of Washington, Seattle, WA, USA
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Tueng T Shen
- School of Medicine, University of Washington, Seattle, WA, USA
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| |
Collapse
|
12
|
Nair A, Ambekar YS, Zevallos-Delgado C, Mekonnen T, Sun M, Zvietcovich F, Singh M, Aglyamov S, Koch M, Scarcelli G, Espana EM, Larin KV. Multiple Optical Elastography Techniques Reveal the Regulation of Corneal Stiffness by Collagen XII. Invest Ophthalmol Vis Sci 2022; 63:24. [PMID: 36383352 PMCID: PMC9680591 DOI: 10.1167/iovs.63.12.24] [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: 08/16/2022] [Accepted: 10/19/2022] [Indexed: 11/17/2022] Open
Abstract
Purpose Collagen XII plays a role in regulating the structure and mechanical properties of the cornea. In this work, several optical elastography techniques were used to investigate the effect of collagen XII deficiency on the stiffness of the murine cornea. Methods A three-prong optical elastography approach was used to investigate the mechanical properties of the cornea. Brillouin microscopy, air-coupled ultrasonic optical coherence elastography (OCE) and heartbeat OCE were used to assess the mechanical properties of wild type (WT) and collagen XII-deficient (Col12a1-/-) murine corneas. The Brillouin frequency shift, elastic wave speed, and compressive strain were all measured as a function of intraocular pressure (IOP). Results All three optical elastography modalities measured a significantly decreased stiffness in the Col12a1-/- compared to the WT (P < 0.01 for all three modalities). The optical coherence elastography techniques showed that mean stiffness increased as a function of IOP; however, Brillouin microscopy showed no discernable trend in Brillouin frequency shift as a function of IOP. Conclusions Our approach suggests that the absence of collagen XII significantly softens the cornea. Although both optical coherence elastography techniques showed an expected increase in corneal stiffness as a function of IOP, Brillouin microscopy did not show such a relationship, suggesting that the Brillouin longitudinal modulus may not be affected by changes in IOP. Future work will focus on multimodal biomechanical models, evaluating the effects of other collagen types on corneal stiffness, and in vivo measurements.
Collapse
Affiliation(s)
- Achuth Nair
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Yogeshwari S. Ambekar
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | | | - Taye Mekonnen
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Mei Sun
- Cornea and External Disease, Department of Ophthalmology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
| | - Fernando Zvietcovich
- Department of Engineering, Pontificia Universidad Catolica del Peru, San Miguel, Lima, Peru
| | - Manmohan Singh
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Salavat Aglyamov
- Department of Mechanical Engineering, University of Houston, Houston, TX, United States
| | - Manuel Koch
- Institute for Dental Research and Oral Musculoskeletal Biology, Center for Molecular Medicine Cologne, and Center for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany
| | - Giuliano Scarcelli
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, United States
| | - Edgar M. Espana
- Cornea and External Disease, Department of Ophthalmology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
| | - Kirill V. Larin
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, United States
| |
Collapse
|
13
|
Regnault G, Kirby MA, Kuriakose M, Shen T, Wang RK, O’Donnell M, Pelivanov I. Spatial resolution in optical coherence elastography of bounded media. BIOMEDICAL OPTICS EXPRESS 2022; 13:4851-4869. [PMID: 36187272 PMCID: PMC9484430 DOI: 10.1364/boe.469019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 07/30/2022] [Accepted: 08/03/2022] [Indexed: 05/11/2023]
Abstract
Dynamic optical coherence elastography (OCE) tracks mechanical wave propagation in the subsurface region of tissue to image its shear modulus. For bulk shear waves, the lateral resolution of the reconstructed modulus map (i.e., elastographic resolution) can approach that of optical coherence tomography (OCT), typically a few tens of microns. Here we perform comprehensive numerical simulations and acoustic micro-tapping OCE experiments to show that for the typical situation of guided wave propagation in bounded media, such as cornea, the elastographic resolution cannot reach the OCT resolution and is mainly defined by the thickness of the bounded tissue layer. We considered the excitation of both broadband and quasi-harmonic guided waves in a bounded, isotropic medium. Leveraging the properties of broadband pulses, a robust method for modulus reconstruction with minimum artifacts at interfaces is demonstrated. In contrast, tissue bounding creates large instabilities in the phase of harmonic waves, leading to serious artifacts in modulus reconstructions.
Collapse
Affiliation(s)
- Gabriel Regnault
- University of Washington, Department of Bioengineering, Seattle, Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
| | - Mitchell A. Kirby
- University of Washington, Department of Bioengineering, Seattle, Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
| | - Maju Kuriakose
- University of Washington, Department of Bioengineering, Seattle, Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
| | - Tueng Shen
- University of Washington, Department of Bioengineering, Seattle, Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
- University of Washington, Department of Ophthalmology, Seattle, Washington, 1959 NE Pacific St, Seattle, WA 98195, USA
| | - Ruikang K. Wang
- University of Washington, Department of Bioengineering, Seattle, Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
- University of Washington, Department of Ophthalmology, Seattle, Washington, 1959 NE Pacific St, Seattle, WA 98195, USA
| | - Matthew O’Donnell
- University of Washington, Department of Bioengineering, Seattle, Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
| | - Ivan Pelivanov
- University of Washington, Department of Bioengineering, Seattle, Washington, 3720 15th Ave NE, Seattle, WA 98105, USA
| |
Collapse
|
14
|
High-frequency ultrasound detects biomechanical weakening in keratoconus with lower stiffness at higher grade. PLoS One 2022; 17:e0271749. [PMID: 35857808 PMCID: PMC9299312 DOI: 10.1371/journal.pone.0271749] [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: 02/28/2022] [Accepted: 07/06/2022] [Indexed: 11/19/2022] Open
Abstract
In vivo biomechanical characterization of the cornea remains a challenge. We have developed a high-frequency ultrasound elastography method, the ocular pulse elastography (OPE), to measure corneal axial displacement (CAD) induced by the ocular pulse. Here we compared CAD and a stiffness index derived from CAD between keratoconus patients and normal controls. We also explored the trend of these parameters with keratoconus grade. Twenty normal subjects and twenty keratoconus patients were recruited in this study. Corneal topography, tomography, intraocular pressure (IOP) and ocular pulse amplitude (OPA) were obtained in each measured eye. The cornea’s heartbeat-induced cyclic axial displacements were measured by high-frequency (50 MHz) ultrasound. A corneal stiffness index (CSI) was derived from CAD normalized against OPA. CAD and CSI were compared between normal and keratoconus groups, and across keratoconus grades. Keratoconus corneas had significantly greater CAD and lower CSI than normal controls (p’s<0.01). Both parameters correlated strongly with grade, in which CAD increased significantly (p = 0.002) and CSI decreased significantly (p = 0.011) with grade. These results suggested a biomechanical weakening in keratoconus which worsens at higher disease severity. This study also demonstrated the ability of high-frequency ultrasound elastography to provide a safe, quick, and accurate evaluation of the cornea’s biomechanical condition in vivo. The OPE-measured biomechanical metrics, when integrated with existing diagnostic criteria, may aid the decision-making in the early and definitive diagnosis and staging of keratoconus.
Collapse
|