scholarly journals Corneal Biomechanical Properties Characterization Using Air-jet Indentation Based Optical Coherence Tomography System (AIOCT)

2019 ◽  
Vol 256 ◽  
pp. 01004 ◽  
Author(s):  
Li-ke Wang ◽  
Jia-ying Zhang ◽  
Tian-jie Li ◽  
Xue-yong Zhang ◽  
Lei Tian ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Tensile Test ◽  
Indentation Test ◽  
Biomechanical Properties ◽  
Tomography System ◽  
Air Jet ◽  
Custom Made ◽  
Mechanical Tensile ◽  
Corneal Biomechanical Properties

We proposed a novel method together with system to quantify the corneal biomechanics. The objectives of this study are to develop a method to measure the corneal biomechanical properties in vivo and to evaluate the performance of AIOCT system. A novel AIOCT system was established and a mathematical model was built on the basis of the current air-jet indentation method. Experiments were performed to evaluate the mechanical properties of eleven custom-made silicone corneal mimicking phantoms by the AIOCT system under different intraocular pressures (IOP). The results were then compared with those measured by the standard mechanical tensile test and indentation test. The phantom’s moduli were ranged from 0.08 to 1.03 MPa according to the tensile and indentation test. The elastic moduli of corneal silicone phantoms (Eairjet) were measured using the AIOCT system with the proposed mathematical model at four IOPs (0.6, 15.3, 29.8, and 44.7 mmHg). The Eairjet were agreed well with the corresponding moduli (Etensile) measured by the tensile test (Eairjet = 1.188 Etensile, R2 = 0.925). The preliminary results showed that this technique was capable of measuring corneal biomechanical properties in vivo and it may provide a clinical potential non-invasive and non-contact means to the diagnosis of keratoconus suspects in the future.

In Vivo and ex Vivo Approaches to Studying the Biomechanical Properties of Healing Wounds in Rat Skin

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Clare Y. L. Chao ◽  
Gabriel Y. F. Ng ◽  
Kwok-Kuen Cheung ◽  
Yong-Ping Zheng ◽  
Li-Ke Wang ◽  
...  
Keyword(s):  
Wound Healing ◽  
Ex Vivo ◽  
Normal Skin ◽  
Biomechanical Properties ◽  
Skin Wound ◽  
Sprague Dawley ◽  
Rat Skin ◽  
Mechanical Stiffness ◽  
Air Jet

An evaluation of wound mechanics is crucial in reflecting the wound healing status. The present study examined the biomechanical properties of healing rat skin wounds in vivo and ex vivo. Thirty male Sprague-Dawley rats, each with a 6 mm full-thickness circular punch biopsied wound at both posterior hind limbs were used. The mechanical stiffness at both the central and margins of the wound was measured repeatedly in five rats over the same wound sites to monitor the longitudinal changes over time of before wounding, and on days 0, 3, 7, 10, 14, and 21 after wounding in vivo by using an optical coherence tomography-based air-jet indentation system. Five rats were euthanized at each time point, and the biomechanical properties of the wound tissues were assessed ex vivo using a tensiometer. At the central wound bed region, the stiffness measured by the air-jet system increased significantly from day 0 (17.2%), peaked at day 7 (208.3%), and then decreased progressively until day 21 (40.2%) as compared with baseline prewounding status. The biomechanical parameters of the skin wound samples measured by the tensiometer showed a marked reduction upon wounding, then increased with time (all p < 0.05). On day 21, the ultimate tensile strength of the skin wound tissue approached 50% of the normal skin; while the stiffness of tissue recovered at a faster rate, reaching 97% of its prewounded state. Our results suggested that it took less time for healing wound tissues to recover their stiffness than their maximal strength in rat skin. The stiffness of wound tissues measured by air-jet could be an indicator for monitoring wound healing and contraction.

scholarly journals Compressional Optical Coherence Elastography of the Cornea

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 111
Author(s):  
Manmohan Singh ◽  
Achuth Nair ◽  
Salavat R. Aglyamov ◽  
Kirill V. Larin
Keyword(s):  
Rabbit Model ◽  
Biomechanical Properties ◽  
Clinical Applications ◽  
Optical Coherence ◽  
Collagen Crosslinking ◽  
Corneal Collagen Crosslinking ◽  
Corneal Biomechanical Properties ◽  
Corneal Collagen

Assessing the biomechanical properties of the cornea is crucial for detecting the onset and progression of eye diseases. In this work, we demonstrate the application of compression-based optical coherence elastography (OCE) to measure the biomechanical properties of the cornea under various conditions, including validation in an in situ rabbit model and a demonstration of feasibility for in vivo measurements. Our results show a stark increase in the stiffness of the corneas as IOP was increased. Moreover, UV-A/riboflavin corneal collagen crosslinking (CXL) also dramatically increased the stiffness of the corneas. The results were consistent across 4 different scenarios (whole CXL in situ, partial CXL in situ, whole CXL in vivo, and partial CXL in vivo), emphasizing the reliability of compression OCE to measure corneal biomechanical properties and its potential for clinical applications.

scholarly journals Attenuation coefficient as a quantitative parameter for analyzing cataracts with optical coherence tomography

2020 ◽  
Vol 238 ◽  
pp. 04004
Author(s):  
Pablo Eugui ◽  
J. Harper Danielle ◽  
Johanna Gesperger ◽  
Antonia Lichtenegger ◽  
Conrad W. Merkle ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Attenuation Coefficient ◽  
Optical Coherence ◽  
Quantitative Parameter ◽  
Swept Source ◽  
Tomography System ◽  
Custom Made ◽  
Significant Difference ◽  
Lens Opacities

Crystalline lenses of mice were imaged in vivo with a custom-made swept-source optical coherence tomography system. The use of the attenuation coefficient as a quantitative parameter for investigating the lens opacities magnitude is proposed, demonstrating a significant difference between the values retrieved from cataractous and normal mouse lenses.

Influence of corneal biomechanical properties on IOP indices in patients with keratoconus

The Eye ◽  
2019 ◽  
Vol 21 (128) ◽  
pp. 15-19
Author(s):  
Irina Bubnova ◽  
Veronica Averich ◽  
Elena Belousova
Keyword(s):  
Disease Progression ◽  
Corneal Thickness ◽  
Central Zone ◽  
Biomechanical Properties ◽  
Resistance Factor ◽  
Corneal Resistance Factor ◽  
Mean Values ◽  
Coefficient Of Elasticity ◽  
D Values ◽  
Corneal Biomechanical Properties

Purpose: Evaluation of corneal biomechanical prop¬erties and their influence on IOP indices in patients with keratoconus. Material and methods. The study included 194 eyes with keratoconus (113 patients aged from 23 to 36 years old). Corneal refraction in central zone varied from 48.25 to 56.75 D, values of corneal thickness ranged from 279 to 558 μm. Patients were divided into 4 groups according to Amsler classification: I stage – 40 eyes; II stage – 78 eyes; III stage – 54 eyes and IV stage – 22 eyes. Standard ophthal¬mological examination was carried out including pneumo¬tonometry. IOP indices and values of biomechanical prop¬erties were evaluated by dynamic bidirectional pneumatic applanation and pneumatic impression. Results. Study of corneal biomechanical properties in patients with keratoconus showed a decrease of such biomechanical indices as corneal hysteresis (CH) on aver¬age to 8.42±1.12 mm Hg, corneal resistance factor (CRF) – to 7.45±0.96 mm Hg, coefficient of elasticity (CE) – 5.35± 0.87 mm Hg. Values of these indices strongly depended on the stage of keratoconus. In the whole sample, the aver¬age corneal compensated IOP (IOPcc) amounted to 15.08± 2.43 mm Hg, Goldman IOP (IOPg) was 11.61±2.37 mm Hg and pneumatic tonometry IOP (IOPp) was 10.13±2.94 mm Hg. IOPcc indices didn’t have any statistically significant differ¬ence in dependence on the stage of keratoconus (р>0.473), while in process of disease progression IOPg and IOPp indi¬ces showed statistically significant decrease of mean values. Conclusion. Progression of keratoconus led to a de¬crease in corneal biomechanical properties which deter¬mine reduction of such indices as IOPg and IOPp in contrast to IOPcc.

scholarly journals Biomechanics of Neutrophil Tethers

Life ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 515
Author(s):  
Andrea Cugno ◽  
Alex Marki ◽  
Klaus Ley
Keyword(s):  
Cell Activation ◽  
Optical Trap ◽  
Biomechanical Properties ◽  
Force Microscopy ◽  
Advantages And Disadvantages ◽  
Atomic Force ◽  
Microfluidic Flow ◽  
Biomembrane Force Probe ◽  
Membrane Reservoir

Leukocytes, including neutrophils, which are propelled by blood flow, can roll on inflamed endothelium using transient bonds between selectins and their ligands, and integrins and their ligands. When such receptor–ligand bonds last long enough, the leukocyte microvilli become extended and eventually form thin, 20 m long tethers. Tether formation can be observed in blood vessels in vivo and in microfluidic flow chambers. Tethers can also be extracted using micropipette aspiration, biomembrane force probe, optical trap, or atomic force microscopy approaches. Here, we review the biomechanical properties of leukocyte tethers as gleaned from such measurements and discuss the advantages and disadvantages of each approach. We also review and discuss viscoelastic models that describe the dependence of tether formation on time, force, rate of loading, and cell activation. We close by emphasizing the need to combine experimental observations with quantitative models and computer simulations to understand how tether formation is affected by membrane tension, membrane reservoir, and interactions of the membrane with the cytoskeleton.

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