scholarly journals Estimation of the Corneal Young’s ModulusIn VivoBased on a Fluid-Filled Spherical-Shell Model with Scheimpflug Imaging

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Po-Jen Shih ◽  
Chun-Ju Huang ◽  
Tzu-Han Huang ◽  
Hung-Chou Lin ◽  
Jia-Yush Yen ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Corneal Thickness ◽  
The Other ◽  
University Hospital ◽  
Scheimpflug Imaging ◽  
Department Of Ophthalmology ◽  
Iop Measurement

Current intraocular pressure (IOP) measurement using air puff could be erroneous without applying proper corrections. Although noncontact tonometry is not considered to be accurate, it is still popularly used by eye clinics. It is thus necessary to extract the correct information from their results. This study proposes a practical approach to correctly measure IOPin vivo. By embedding a new model-based correction to the Corvis® ST, we can extract the corneal Young’s modulus from the patient data. This Young’s modulus can be used to correct the IOP readings. The tests were applied to 536 right eyes of 536 healthy subjects (228 male and 308 female) between March of 2012 and April of 2016. The tests were applied to patients at the Department of Ophthalmology, National Taiwan University Hospital and the Hung-Chuo Eye Clinics. The statistical analysis showed that the value for the Young’s modulus was independent of all the other parameters collected from the Corvis ST, including the corneal thickness and the intraocular pressure. Therefore, it is important to independently measure the Young’s modulus instead of depending on the correlation with the other parameters. This study adds the methodology of measuring corneal stiffnessin vivofor ophthalmologists’ reference in diagnosis.

scholarly journals Changes in Intraocular Pressure after Transepithelial Photorefractive Keratectomy and Femtosecond Laser In Situ Keratomileusis

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Chien-Chih Chou ◽  
Po-Jen Shih ◽  
Hung-Chou Lin ◽  
Jun-Peng Chen ◽  
Jia-Yush Yen ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Femtosecond Laser ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Laser In Situ Keratomileusis ◽  
Photorefractive Keratectomy ◽  
Linear Regression Models ◽  
Postoperative Changes

Purpose. To investigate the changes in intraocular pressure (IOP) and biomechanically corrected IOP (bIOP) in patients undergoing transepithelial photorefractive keratectomy (TPRK) and femtosecond laser in situ keratomileusis (FS-LASIK) and to determine the effects of preoperative biomechanical factors on IOP and bIOP changes after FS-LASIK and TPRK. Design. A retrospective comparative study. Methods. We retrospectively investigated the IOP and corneal biomechanical changes in 93 eyes undergoing FS-LASIK and 104 eyes undergoing TPRK in a clinical setting. Preoperative and postoperative data on ophthalmic and Corvis ST examinations, in vivo Young’s modulus, and noncontact tonometry were analyzed. Marginal linear regression models with generalized estimating equations were used for intragroup and intergroup comparisons of IOP and bIOP changes. Results. In the univariate model, IOP reduction after FS-LASIK was 2.49 mmHg higher than that after TPRK. In addition, bIOP reduction after FS-LASIK was 1.85 mmHg higher than that after TPRK. In the multiple regression model, we revealed that IOP reduction after FS-LASIK was 1.75 mmHg higher than that after TPRK. Additionally, bIOP reduction after FS-LASIK was 1.64 mmHg higher than that after TPRK. Postoperative changes in bIOP were less than those in IOP. In addition, Young’s modulus and CBI had no significant effect on postoperative IOP and bIOP changes. We establish a biomechanically predictive model using the available data to predict postoperative IOP and bIOP changes after TPRK and FS-LASIK. Conclusions. Reductions in IOP and bIOP after FS-LASIK were 1.75 mmHg and 1.64 mmHg, respectively, more than those after TPRK, after adjustment for confounders. We revealed that the type of refractive surgery and peak distance (PD) were significant predictors of postoperative IOP and bIOP changes. By contrast, depth of ablation showed a significant effect on only IOP changes.

scholarly journals Morphology and Mechanical Properties of Plantar Fascia in Flexible Flatfoot: A Noninvasive In Vivo Study

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhihui Qian ◽  
Zhende Jiang ◽  
Jianan Wu ◽  
Fei Chang ◽  
Jing Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Plantar Fascia ◽  
The Other ◽  
Flexible Flatfoot ◽  
Significant Difference ◽  
Peak Pressures ◽  
Morphology And Mechanical Properties

Plantar fascia plays an important role in human foot biomechanics; however, the morphology and mechanical properties of plantar fascia in patients with flexible flatfoot are unknown. In this study, 15 flexible flatfeet were studied, each plantar fascia was divided into 12 positions, and the morphologies and mechanical properties in the 12 positions were measured in vivo with B-mode ultrasound and shear wave elastography (SWE). Peak pressures under the first to fifth metatarsal heads (MH) were measured with FreeStep. Statistical analysis included 95% confidence interval, intragroup correlation coefficient (ICC1,1), one-way analysis of variance (one-way ANOVA), and least significant difference. The results showed that thickness and Young’s modulus of plantar fascia were the largest at the proximal fascia (PF) and decreased gradually from the proximal end to the distal end. Among the five distal branches (DB) of the fascia, the thickness and Young’s modulus of the second and third DB were larger. The peak pressures were also higher under the second and third MH. This study found a gradient distribution in that the thickness and Young’s modulus gradient decreased from the proximal end to the distal end of plantar fascia in the longitudinal arch of flexible flatfeet. In the transverse arch, the thickness and Young’s modulus under the second and third DB were larger than those under the other three DB in flexible flatfoot, and the peak pressures under the second and third MH were also larger than those under the other three MH in patients with flexible flatfoot. These findings deepen our understanding of the changes of biomechanical properties and may be meaningful for the study of pathological mechanisms and therapy for flexible flatfoot.

scholarly journals Intraocular pressure and choroidal thickness postural changes in multiple system atrophy and Parkinson’s disease

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maddalena De Bernardo ◽  
Giulio Salerno ◽  
Marco Gioia ◽  
Luigi Capasso ◽  
Maria Claudia Russillo ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Intraocular Pressure ◽  
Multiple System Atrophy ◽  
Choroidal Thickness ◽  
Corneal Thickness ◽  
Standing Position ◽  
Sitting Position ◽  
Postural Changes ◽  
Iop Measurement

AbstractTo evaluate intraocular pressure (IOP) and choroidal thickness (ChT) postural changes in multiple system atrophy (MSA), Parkinson’s disease (PD) patients and healthy controls (HC). 20 MSA patients, 21 PD patients and 14 HC, were examined. All subjects underwent a complete examination, including corneal thickness, ChT, IOP and axial length (AL) measurements. IOP measurement was performed in supine, sitting, and standing positions, whereas ChT in sitting and standing positions. Supine to standing IOP variations were significantly higher in MSA vs PD(p = 0.01) and in MSA vs HC (p < 0.0001), whereas no significant differences were observed between PD and HC (p = 0.397). Mean sub-foveal ChT in MSA was 240 ± 92 μm in sitting position, and 215 ± 94 μm in standing position with a significant reduction (p = 0.008). Mean sub-foveal ChT in PD was 258 ± 79 μm in sitting position, and 259 ± 76 μm in standing position (p = 0.887). In HC it was 244 ± 36 μm in sitting position, and 256 ± 37 μm in standing position with a significant increase (p = 0.007). The significant IOP and ChT postural changes can be considered additional hallmarks of autonomic dysfunction in MSA and further studies are needed to consider them as biomarkers in the differential diagnosis with PD.

A dynamical method for the determination of Young's modulus by stretching

1928 ◽  
Vol 24 (2) ◽  
pp. 276-279
Author(s):  
C. F. Sharman
Keyword(s):  
Young’S Modulus ◽  
Elastic Constants ◽  
Young's Modulus ◽  
The Other ◽  
Static Deformation ◽  
Elastic Forces ◽  
Dynamical Method ◽  
Period Of Oscillation

There are two general methods of measuring the elastic constants of bodies; one involves a study of the static deformation produced by the appropriate kind of stress, and the other a measurement of the period of oscillation of a system of known inertia under the elastic forces.

scholarly journals Benefits of Nonthermal Atmospheric Plasma Treatment on Dentin Adhesion

2018 ◽  
Vol 43 (6) ◽  
pp. E288-E299 ◽  
Author(s):  
AP Ayres ◽  
PH Freitas ◽  
J De Munck ◽  
A Vananroye ◽  
C Clasen ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Water Storage ◽  
Contact Angles ◽  
The Other ◽  
Atmospheric Plasma ◽  
Hybrid Layer ◽  
Water Contact ◽  
Dentin Surface

SUMMARY Objectives: This study aimed to evaluate the influence of two nonthermal atmospheric plasma (NTAP) application times and two storage times on the microtensile bond strength (μTBS) to dentin. The influence of NTAP on the mechanical properties of the dentin-resin interface was studied by analyzing nanohardness (NH) and Young's modulus (YM). Water contact angles of pretreated dentin and hydroxyapatite blocks were also measured to assess possible alterations in the surface hydrophilicity upon NTAP. Methods and Materials: Forty-eight human molars were used in a split-tooth design (n=8). Midcoronal exposed dentin was flattened by a 600-grit SiC paper. One-half of each dentin surface received phosphoric acid conditioning, while the other half was covered with a metallic barrier and remained unetched. Afterward, NTAP was applied on the entire dentin surface (etched or not) for 10 or 30 seconds. The control groups did not receive NTAP treatment. Scotchbond Universal (SBU; 3M ESPE) and a resin-based composite were applied to dentin following the manufacturer's instructions. After 24 hours of water storage at 37°C, the specimens were sectioned perpendicular to the interface to obtain approximately six specimens or bonded beams (approximately 0.9 mm2 in cross-sectional area) representing the etch-and-rinse (ER) approach and another six specimens representing the self-etch (SE) approach. Half of the μTBS specimens were immediately loaded until failure, while the other half were first stored in deionized water for two years. Three other bonded teeth were selected from each group (n=3) for NH and YM evaluation. Water contact-angle analysis was conducted using a CAM200 (KSV Nima) goniometer. Droplet images of dentin and hydroxyapatite surfaces with or without 10 or 30 seconds of plasma treatment were captured at different water-deposition times (5 to 55 seconds). Results: Two-way analysis of variance revealed significant differences in μTBS of SBU to dentin after two years of water storage in the SE approach, without differences among treatments. After two years of water aging, the ER control and ER NTAP 10-second groups showed lower μTBS means compared with the ER NTAP 30-second treated group. Nonthermal atmospheric plasma resulted in higher NH and YM for the hybrid layer. The influence of plasma treatment in hydrophilicity was more evident in the hydroxyapatite samples. Dentin hydrophilicity increased slightly after 10 seconds of NTAP, but the difference was higher when the plasma was used for 30 seconds. Conclusions: Dentin NTAP treatment for 30 seconds contributed to higher μTBS after two years of water storage in the ER approach, while no difference was observed among treatments in the SE evaluation. This result might be correlated to the increase in nanohardness and Young's modulus of the hybrid layer and to better adhesive infiltration, since dentin hydrophilicity was also improved. Although some effects were observed using NTAP for 10 seconds, the results suggest that 30 seconds is the most indicated treatment time.

scholarly journals Effect of Acute Increases in Intraocular Pressure on Corneal Pachymetry in Rabbit Eyes Treated with Timolol Maleate

2018 ◽  
Vol 12 (1) ◽  
pp. 314-321
Author(s):  
Cristina Sánchez-Barahona ◽  
Gema Bolívar ◽  
Dimitrios G. Mikropoulos ◽  
Anastasios G. Konstas ◽  
Miguel A. Teus
Keyword(s):  
Intraocular Pressure ◽  
Anterior Chamber ◽  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Rabbit Model ◽  
Controlled Study ◽  
Control Group ◽  
Study Group ◽  
Timolol Maleate

Objective: To evaluate in an in vivo rabbit model, the effect of topical timolol maleate therapy on the central corneal thickness response to acute intraocular pressure increases. Method: In this prospective and interventional controlled study, the central corneal thickness and intraocular pressure were measured in vivo in 12 rabbit eyes treated with topical timolol maleate for 1 month and in 12 controls at baseline, and after the intraocular pressure (measured by direct cannulation of the anterior chamber) was increased to 15 and 30 mmHg using a forced saline infusion into the anterior chamber. Results: There were no significant differences in the basal central corneal thickness values (control group, 373.2±12.9 µm; study group, 377.5±19.2 µm, p=0.5) or the central corneal thickness values when the intraocular pressure was increased to 15 mmHg (control group, 335.2±14.3 µm; study group, 330.0±32.1 µm, p=0.6) and to 30 mmHg (study group, 318.8±25.3 µm; control group, 329.8±21.0 µm, p=0.3). Conclusion: Rabbit corneas treated with topical timolol maleate for 1 month did not show a strain response to acute intraocular pressure increases that differed from control eyes. This is in contrast to a previous finding in which rabbit eyes treated with prostaglandin analogues had a greater decrease in central corneal thickness in response to a sudden intraocular pressure increase compared with untreated corneas.

scholarly journals Technical Note: In vivo Young's modulus mapping of pancreatic ductal adenocarcinoma during HIFU ablation using harmonic motion elastography ( HME )

2018 ◽  
Vol 45 (11) ◽  
pp. 5244-5250 ◽  
Author(s):  
Alireza Nabavizadeh ◽  
Thomas Payen ◽  
Niloufar Saharkhiz ◽  
Matthew McGarry ◽  
Kenneth P. Olive ◽  
...  
Keyword(s):  
Pancreatic Ductal Adenocarcinoma ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Technical Note ◽  
Ductal Adenocarcinoma ◽  
Harmonic Motion ◽  
Hifu Ablation

scholarly journals Intraocular Pressure Measurement Using Ocular Response Analyzer, Dynamic Contour Tonometer, and Scheimpflug Analyzer Corvis ST

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Lisa Ramm ◽  
Robert Herber ◽  
Eberhard Spoerl ◽  
Frederik Raiskup ◽  
Lutz E. Pillunat ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Healthy Subjects ◽  
Corneal Thickness ◽  
Applanation Tonometry ◽  
Ocular Response Analyzer ◽  
Corvis St ◽  
Dynamic Contour Tonometer ◽  
Iop Measurement ◽  
Good Agreement

Purpose. To compare intraocular pressure (IOP) measurements with Goldmann applanation tonometry (GAT), ocular response analyzer (ORA), dynamic contour tonometer (DCT), and Corvis ST (CST) in healthy subjects. Methods. In a prospective, observational study, IOP measurements with GAT (GAT-IOPc), ORA (IOPcc), DCT (DCT-IOP), and CST (bIOP) were performed and analyzed in 94 healthy subjects. Results. Mean age of the participants was 45.6 ± 17.2 years (range 18 to 81 years). Mean GAT-IOPc was 12.9 ± 2.4 mmHg, mean DCT-IOP was 16.1 ± 2.6 mmHg, and mean IOPcc was 15.6 ± 3.3 mmHg. DCT-IOP and IOPcc were significantly higher than GAT-IOPc (P<0.001). Mean bIOP was 13.5 ± 2.4 mmHg that was slightly higher but not significantly different from GAT-IOPc (P=0.146). Correlation analysis of IOP values and central corneal thickness (CCT) revealed a negative correlation between GAT-IOPc and CCT (r = −0.347; P=0.001). However, IOPcc, DCT-IOP, and bIOP showed no significant correlation to CCT. Only bIOP revealed a weak but significant age dependency (r = 0.321, P=0.002). Conclusion. All tonometry devices showed a good agreement of biomechanical corrected IOP values with GAT-IOPc. As no influence of CCT on IOPcc, DCT-IOP, and bIOP was detectable, the used correction algorithms appear to be appropriate in these tonometers in the clinical setting. The highest agreement was found between GAT-IOPc and bIOP. However, bIOP weakly correlated with participants’ age. Further studies are needed to elucidate the role of bIOP for IOP measurement.

Nonisometric behavior of fascicles during isometric contractions of a human muscle

1998 ◽  
Vol 85 (4) ◽  
pp. 1230-1235 ◽  
Author(s):  
Masamitsu Ito ◽  
Yasuo Kawakami ◽  
Yoshiho Ichinose ◽  
Senshi Fukashiro ◽  
Tetsuo Fukunaga
Keyword(s):  
Young’S Modulus ◽  
Joint Angle ◽  
Young's Modulus ◽  
Pennation Angle ◽  
Human Muscle ◽  
Isometric Contractions ◽  
Fascicle Length ◽  
Tendon Stiffness ◽  
Tendon Elongation

Fascicle length, pennation angle, and tendon elongation of the human tibialis anterior were measured in vivo by ultrasonography. Subjects ( n = 9) were requested to develop isometric dorsiflexion torque gradually up to maximal at the ankle joint angle of 20° plantarflexion from the anatomic position. Fascicle length shortened from 90 ± 7 to 76 ± 7 (SE) mm, pennation angle increased from 10 ± 1 to 12 ± 1°, and tendon elongation increased up to 15 ± 2 mm with graded force development up to maximum. The tendon stiffness increased with increasing tendon force from 10 N/mm at 0–20 N to 32 N/mm at 240–260 N. Young’s modulus increased from 157 MPa at 0–20 N to 530 MPa at 240–260 N. It can be concluded that, in isometric contractions of a human muscle, mechanical work, some of which is absorbed by the tendinous tissue, is generated by the shortening of muscle fibers and that ultrasonography can be used to determine the stiffness and Young’s modulus for human tendons.

Low-frequency viscoelastic properties of canine femoral artery in vivo

1979 ◽  
Vol 236 (5) ◽  
pp. H720-H724
Author(s):  
P. Sipkema
Keyword(s):  
Young’S Modulus ◽  
Femoral Artery ◽  
Constant Pressure ◽  
Young's Modulus ◽  
Low Frequency ◽  
Absolute Value ◽  
Average Value ◽  
Mean Pressure ◽  
Frequency Behavior

Mechanical properties of the canine femoral artery in vivo are measured as a function of frequency (0.0025--0.1 Hz) and as a function of mean pressure (10--16 kPa). Sinusoidal pressure variations are generated with a servo-controlled occluder system. The absolute value of the Young's modulus increases with mean pressure (E = 0.63 X 10(5) exp(0.211P)-N.m-2) at 0.05 Hz; where P is pressure. At heart rate frequencies (average value 2.22 Hz) this relation is: E = 1.25 X 10(5) exp(0.175P) N.m-2. The phase angle of the Young's modulus is independent of pressure at both frequencies. At 0.05 Hz we found: phi = 0.189 - 0.00788 P radians and at 2.22 Hz: phi = 0.0723 + 0.000428 P. The slope of both lines is not significantly different from zero slope (alpha = 0.05). Frequency dependence is studied at a constant pressure level (Pr, average value 14.3 kPa) just below the animals' mean pressure levels (average value 15.9 kPa). The frequency behavior of the elastic modulus is fitted with a function with two poles and two zeros (poles at 0.003 and 0.038 Hz; zeros at 0.0022 and 0.03 Hz).

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