Investigating Elastic Anisotropy of the Porcine Cornea as a Function of Intraocular Pressure With Optical Coherence Elastography

Singh, Manmohan; Li, Jiasong; Han, Zhaolong; Wu, Chen; Aglyamov, Salavat R.; Twa, Michael D.; Larin, Kirill V.

doi:10.3928/1081597x-20160520-01

Cited by 53 publications

(56 citation statements)

References 26 publications

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“…Once again, these studies were conducted under different conditions. More comparably, our own work that showed an approximate 50% increase in stiffness was obtained on rabbit eyes (Singh et al, 2016b), and strip extensiometry has shown a noticeable difference in stiffness changes between human and rabbit eyes, indicating that structural differences between species may also be a contributing factor to corneal stiffening by CXL (Wollensak et al, 2003b). …”

Section: Discussionmentioning

confidence: 65%

“…In this work, 501 M-mode scans were taken over a 7 mm line, which was along the nasal/temporal axis of the cornea. OCE measurements were made at IOPs of 15, 20, 25, and 30 mmHg before and after the CXL treatment and along the same axis to minimize effects of the elastic anisotropy of the cornea (Elsheikh et al, 2008b; Nguyen et al, 2014; Pinsky et al, 2005; Singh et al, 2016b). …”

Section: Methodsmentioning

confidence: 99%

“…Similar to traditional elastographic techniques, OCE utilizes its parent imaging modality of OCT to detect externally induced displacements within tissue. Due to the high resolution and noncontact nature of OCT, OCE is particularly well suited for assessing the biomechanical properties of the cornea (Ford et al, 2011; Ford et al, 2014; Han et al, 2015b; Li et al, 2014a; Li et al, 2013; Li et al, 2014b; Qu et al, 2016; Singh et al, 2016a; Singh et al, 2016b; Singh et al, 2016c; Singh et al, 2015; Twa et al, 2014; Wang and Larin, 2014a, b). …”

Section: Introductionmentioning

confidence: 99%

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Optical coherence elastography assessment of corneal viscoelasticity with a modified Rayleigh-Lamb wave model

Han

Singh

et al. 2017

Journal of the Mechanical Behavior of Biomedical Materials

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100

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The biomechanical properties of the cornea play a critical role in forming vision. Diseases such as keratoconus can structurally degenerate the cornea causing a pathological loss in visual acuity. UV-A/riboflavin corneal collagen crosslinking (CXL) is a clinically available treatment to stiffen the cornea and restore its healthy shape and function. However, current CXL techniques do not account for pre-existing biomechanical properties of the cornea nor the effects of the CXL treatment itself. In addition to the inherent corneal structure, the intraocular pressure (IOP) can also dramatically affect the measured biomechanical properties of the cornea. In this work, we present the details and development of a modified Rayleigh-Lamb frequency equation model for quantifying corneal biomechanical properties. After comparison with finite element modeling, the model was utilized to quantify the viscoelasticity of in situ porcine corneas in the whole eye-globe configuration before and after CXL based on noncontact optical coherence elastography measurements. Moreover, the viscoelasticity of the untreated and CXL-treated eyes was quantified at various IOPs. The results showed that the stiffness of the cornea increased after CXL and that corneal stiffness is close to linear as a function of IOP. These results show that the modified Rayleigh-Lamb wave model can provide an accurate assessment of corneal viscoelasticity, which could be used for customized CXL therapies.

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Section: Discussionmentioning

confidence: 65%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical coherence elastography assessment of corneal viscoelasticity with a modified Rayleigh-Lamb wave model

Han

Singh

et al. 2017

Journal of the Mechanical Behavior of Biomedical Materials

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100

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“…40 Previously, we have evaluated the effect of intraocular pressure on the measured corneal biomechanical properties using air-pulse optical coherence elastography methods and showed a linear increase in corneal stiffness with an increase in intraocular pressure. 46,47 In this study, we evaluated the effect of tissue thickness on the measured corneal biomechanical properties using dynamic optical coherence elastography.…”

Section: Discussionmentioning

confidence: 99%

Effects of Thickness on Corneal Biomechanical Properties Using Optical Coherence Elastography

Vantipalli

Singh

et al. 2018

Optom Vis Sci

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SIGNIFICANCE: Measured corneal biomechanical properties are driven by intraocular pressure, tissue thickness, and inherent material properties. We demonstrate tissue thickness as an important factor in the measurement of corneal biomechanics that can confound short-term effects due to UV riboflavin cross-linking (CXL) treatment. PURPOSE: We isolate the effects of tissue thickness on the measured corneal biomechanical properties using optical coherence elastography by experimentally altering the tissue hydration state and stiffness. METHODS: Dynamic optical coherence elastography was performed using phase-sensitive optical coherence tomography imaging to quantify the tissue deformation dynamics resulting from a spatially discrete, low-force air pulse (150-μm spot size; 0.8-millisecond duration; <10 Pa [<0.08 mmHg]). The time-dependent surface deformation is characterized by a viscoelastic tissue recovery response, quantified by an exponential decay constant—relaxation rate. Ex vivo rabbit globes (n = 10) with fixed intraocular pressure (15 mmHg) were topically instilled every 5 minutes with 0.9% saline for 60 minutes and 20% dextran for another 60 minutes. Measurements were made after every 20 minutes to determine the central corneal thickness (CCT) and the relaxation rates. Cross-linking treatment was performed on another 13 eyes, applying isotonic riboflavin (n = 6) and hyper-tonic riboflavin (n = 7) every 5 minutes for 30 minutes, followed by UV irradiation (365 nm, 3 mW/cm2) for 30 minutes while instilling riboflavin. Central corneal thickness and relaxation rates were obtained before and after CXL treatment. RESULTS: Corneal thickness was positively correlated (R2 = 0.9) with relaxation rates. In the CXL-treated eyes, iso-tonic riboflavin did not affect CCT and showed a significant increase in relaxation rates (+10%; P = .01) from2.29 ms−1 to 2.53 ms−1. Hypertonic riboflavin showed a significant CCT decrease (−31%; P = .01) from 618 μm to 429 μm but showed little change in relaxation rates after CXL treatment. CONCLUSIONS: Corneal thickness and stiffness are correlated positively. A higher relaxation rate implied stiffer material properties after isotonic CXL treatment. Hypertonic CXL treatment results in a stiffness decrease that offsets the stiffness increase with CXL treatment.

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“…Point dynamic loading is attractive as a source of shear waves, and an attractive noncontact localized method is the micro-air puff developed and applied extensively by the Larin group [45, 57, 63, 81, [97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114][115][116], mainly to the cornea, but also to skin [108,116], cardiac and skeletal muscles [104], cartilage [101,106], fat and soft tissue tumors [97], and kidneys [112]. Similar to ARF-based excitation, an air puff can deliver a localized and well-controlled impulse stimulus, which can be accompanied by measurement of the tissue displacement or measurement of the air puff-induced elastic wave.…”

Section: Loading Methodsmentioning

confidence: 99%

Optical coherence elastography – OCT at work in tissue biomechanics [Invited]

Larin

Sampson

2017

Biomed. Opt. Express

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Abstract:Optical coherence elastography (OCE), as the use of OCT to perform elastography has come to be known, began in 1998, around ten years after the rest of the field of elastography -the use of imaging to deduce mechanical properties of tissues. After a slow start, the maturation of OCT technology in the early to mid 2000s has underpinned a recent acceleration in the field. With more than 20 papers published in 2015, and more than 25 in 2016, OCE is growing fast, but still small compared to the companion fields of cell mechanics research methods, and medical elastography. In this review, we describe the early developments in OCE, and the factors that led to the current acceleration. Much of our attention is on the key recent advances, with a strong emphasis on future prospects, which are exceptionally bright.

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Investigating Elastic Anisotropy of the Porcine Cornea as a Function of Intraocular Pressure With Optical Coherence Elastography

Cited by 53 publications

References 26 publications

Optical coherence elastography assessment of corneal viscoelasticity with a modified Rayleigh-Lamb wave model

Optical coherence elastography assessment of corneal viscoelasticity with a modified Rayleigh-Lamb wave model

Effects of Thickness on Corneal Biomechanical Properties Using Optical Coherence Elastography

Optical coherence elastography – OCT at work in tissue biomechanics [Invited]

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