Mechanical Deformation of Peripapillary Retina in Response to Acute Intraocular Pressure Elevation

2022 ◽  
Author(s):  
Sunny Kwok ◽  
Manqi Pan ◽  
Nicholas Hazen ◽  
Xueliang Pan ◽  
Jun Liu
Keyword(s):  
Intraocular Pressure ◽  
High Frequency ◽  
Mechanical Deformation ◽  
Ultrasound Elastography ◽  
Radial Compression ◽  
High Shear ◽  
High Frequency Ultrasound ◽  
Tangential Strain ◽  
Frequency Ultrasound ◽  
Peripapillary Retina

Abstract Elevated intraocular pressure (IOP) may cause mechanical injuries to the optic nerve head (ONH) and the peripapillary tissues in glaucoma. Previous studies have reported the mechanical deformation of the ONH and the peripapillary sclera (PPS) at elevated IOP. The deformation of the peripapillary retina (PPR) has not been well-characterized. Here we applied high-frequency ultrasound elastography to map and quantify PPR deformation, and compared PPR, PPS and ONH deformation in the same eye. Whole globe inflation was performed in ten human donor eyes. High-frequency ultrasound scans of the posterior eye were acquired while IOP was raised from 5 to 30 mmHg. A correlation-based ultrasound speckle tracking algorithm was used to compute pressure-induced displacements within the scanned tissue cross-sections. Radial, tangential, and shear strains were calculated for the PPR, PPS, and ONH regions. In PPR, shear was significantly larger in magnitude than radial and tangential strains. Strain maps showed localized high shear and high tangential strains in PPR. In comparison to PPS and ONH, PPR had greater shear and a similar level of tangential strain. Surprisingly, PPR radial compression was minimal and significantly smaller than that in PPS. These results provide new insights into PPR deformation in response of IOP elevation, suggesting that shear rather than compression was likely the primary mode of IOP-induced mechanical insult in PPR. High shear, especially localized high shear, may contribute to the mechanical damage of this tissue in glaucoma.

Regional variation of corneal stromal deformation measured by high-frequency ultrasound elastography

2021 ◽  
pp. 153537022110292
Author(s):  
Sunny Kwok ◽  
Nicholas Hazen ◽  
Keyton Clayson ◽  
Xueliang Pan ◽  
Jun Liu
Keyword(s):  
Intraocular Pressure ◽  
Cross Section ◽  
High Frequency ◽  
Regional Variation ◽  
Corneal Stroma ◽  
Ultrasound Elastography ◽  
High Frequency Ultrasound ◽  
Intraocular Pressure Elevation ◽  
Shear Strains ◽  
Frequency Ultrasound

The cornea’s mechanical response to intraocular pressure elevations may alter in ectatic diseases such as keratoconus. Regional variations of mechanical deformation in normal and keratoconus eyes during intraocular pressure elevation have not been well-characterized. We applied a high-frequency ultrasound elastography technique to characterize the regional deformation of normal and keratoconus human corneas through the full thickness of corneal stroma. A cross-section centered at the corneal apex in 11 normal and 2 keratoconus human donor eyes was imaged with high-frequency ultrasound during whole globe inflation from 5 to 30 mmHg. An ultrasound speckle tracking algorithm was used to compute local tissue displacements. Radial, tangential, and shear strains were mapped across the imaged cross-section. Strains in the central (1 mm surrounding apex) and paracentral (1 to 4 mm from apex) regions were analyzed in both normal and keratoconus eyes. Additional regional analysis was performed in the eye with severe keratoconus presenting significant thinning and scarring. Our results showed that in normal corneas, the central region had significantly smaller tangential stretch than the paracentral region, and that within the central region, the magnitudes of radial and shear strains were significantly larger than that of tangential strain. The eye with mild keratoconus had similar shear strain but substantially larger radial strains than normal corneas, while the eye with severe keratoconus had similar overall strains as in normal eyes but marked regional heterogeneity and large strains in the cone region. These findings suggested regional variation of mechanical responses to intraocular pressure elevation in both normal and keratoconus corneas, and keratoconus appeared to be associated with mechanical weakening in the cone region, especially in resisting radial compression. Comprehensive characterization of radial, tangential, and shear strains through corneal stroma may provide new insights to understand the biomechanical alterations in keratoconus.

Ex Vivo Evaluation of Mouse Brain Elasticity Using High-Frequency Ultrasound Elastography

2019 ◽  
Vol 66 (12) ◽  
pp. 3426-3435
Author(s):  
Fang-Yi Lay ◽  
Pei-Yu Chen ◽  
Hsiang-Fan Cheng ◽  
Yu-Min Kuo ◽  
Chih-Chung Huang
Keyword(s):  
Mouse Brain ◽  
High Frequency ◽  
Ex Vivo ◽  
Ultrasound Elastography ◽  
High Frequency Ultrasound ◽  
Frequency Ultrasound

Intraocular Pressure–dependent Corneal Elasticity Measurement Using High-frequency Ultrasound

2019 ◽  
Vol 41 (5) ◽  
pp. 251-270 ◽  
Author(s):  
Laurentius O. Osapoetra ◽  
Dan M. Watson ◽  
Stephen A. McAleavey
Keyword(s):  
Intraocular Pressure ◽  
High Resolution ◽  
High Frequency ◽  
Wave Speed ◽  
Biomechanical Properties ◽  
Single Element ◽  
High Frequency Ultrasound ◽  
Spatially Resolved ◽  
Corneal Biomechanical Properties ◽  
Frequency Ultrasound

Measurement of corneal biomechanical properties can aid in predicting corneal responses to diseases and surgeries. For delineation of spatially resolved distribution of corneal elasticity, high-resolution elastography system is required. In this study, we demonstrate a high-resolution elastography system using high-frequency ultrasound for ex-vivo measurement of intraocular pressure (IOP)-dependent corneal wave speed. Tone bursts of 500 Hz vibrations were generated on the corneal surface using an electromagnetic shaker. A 35-MHz single-element transducer was used to track the resulting anti-symmetrical Lamb wave in the cornea. We acquired spatially resolved wave speed images of the cornea at IOPs of 7, 11, 15, 18, 22, and 29 mmHg. The IOP dependence of corneal wave speed is apparent from these images. Statistical analysis of measured wave speed as a function of IOP revealed a linear relation between wave speed and IOP cs = 0.37 + 0.22 × IOP, with the coefficient of determination R2 = 0.86. We also observed depth-dependent variations of wave speed in the cornea, decreasing from anterior toward posterior. This depth dependence is more pronounced at higher IOP values. This study demonstrates the potential of high-frequency ultrasound elastography in the characterization of spatially resolved corneal biomechanical properties.

scholarly journals Three-Dimensional Inflation Response of Porcine Optic Nerve Head Using High-Frequency Ultrasound Elastography

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Yanhui Ma ◽  
Elias Pavlatos ◽  
Keyton Clayson ◽  
Sunny Kwok ◽  
Xueliang Pan ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Optic Nerve Head ◽  
High Frequency ◽  
Three Dimensional ◽  
3D Ultrasound ◽  
Least Square ◽  
Ultrasound Elastography ◽  
High Frequency Ultrasound ◽  
Biomechanical Behavior ◽  
Frequency Ultrasound

Abstract Characterization of the biomechanical behavior of the optic nerve head (ONH) in response to intraocular pressure (IOP) elevation is important for understanding glaucoma susceptibility. In this study, we aimed to develop and validate a three-dimensional (3D) ultrasound elastographic technique to obtain mapping and visualization of the 3D distributive displacements and strains of the ONH and surrounding peripapillary tissue (PPT) during whole globe inflation from 15 to 30 mmHg. 3D scans of the posterior eye around the ONH were acquired through full tissue thickness with a high-frequency ultrasound system (50 MHz). A 3D cross-correlation-based speckle-tracking algorithm was used to compute tissue displacements at ∼30,000 kernels distributed within the region of interest (ROI), and the components of the strain tensors were calculated at each kernel by using least square estimation of the displacement gradients. The accuracy of displacement calculation was evaluated using simulated rigid-body translation on ultrasound radiofrequency (RF) data obtained from a porcine posterior eye. The accuracy of strain calculation was evaluated using finite element (FE) models. Three porcine eyes were tested showing that ONH deformation was heterogeneous with localized high strains. Substantial radial (i.e., through-thickness) compression was observed in the anterior ONH and out-of-plane (i.e., perpendicular to the surface of the shell) shear was shown to concentrate in the vicinity of ONH/PPT border. These preliminary results demonstrated the feasibility of this technique to achieve comprehensive 3D evaluation of the mechanical responses of the posterior eye, which may provide mechanistic insights into the regional susceptibility in glaucoma.

Characterization of Hand Tendons Through High-Frequency Ultrasound Elastography

2020 ◽  
Vol 67 (1) ◽  
pp. 37-48
Author(s):  
Pei-Yu Chen ◽  
Tai-Hua Yang ◽  
Li-Chieh Kuo ◽  
Cho-Chiang Shih ◽  
Chih-Chung Huang
Keyword(s):  
High Frequency ◽  
Ultrasound Elastography ◽  
High Frequency Ultrasound ◽  
Frequency Ultrasound
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