scholarly journals Direct Evidence of Symmetry between Bilateral Human Corneas in Biomechanical Properties: A Comparison Study with Fresh Corneal Tissue

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Chao Xue ◽  
Yaoqi Xiang ◽  
Yi Song ◽  
Min Shen ◽  
Di Wu ◽  
...  
Keyword(s):  
Biomechanical Properties ◽  
Tangent Modulus ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Corneal Tissue ◽  
Significant Difference ◽  
Lenticule Extraction ◽  
The Difference ◽  
First Time ◽  
Corneal Biomechanical Properties

Purpose. To investigate the difference between the eyes from the same human with respect to the biomechanical properties of fresh corneal tissues and investigate the assumption of similarity of the corneal biomechanical properties between the eyes. Methods. Strip specimens extracted through a small incision lenticule extraction (SMILE) surgery were tested using a uniaxial tensile test. The specimens were extracted vertically. Low-strain tangent modulus (LSTM), high-strain tangent modulus (HSTM), and tensile strength ( σ b ) were the biomechanical parameters used in the comparison of the eyes from the same human. Results. Ninety corneal specimens from 45 persons were included in this study. The LSTM of the left and right eyes were 1.34 ± 0.52 and 1.37 ± 0.46 MPa, while the HSTM were 50.53 ± 7.51 and 49.41 ± 7.01 MPa, respectively. There was no significant difference between the eyes in terms of LSTM, HSTM, and σ b P = 0.813 ,   0.335 ,   and  0.605 ,   resp . . The LSTM and HSTM were significantly correlated with the spherical equivalent (SE) ( P ≤ 0.01 ,   P = 0.001 , resp.). Conclusions. The assumption that the corneal biomechanical properties of the eyes from the same human are similar has been confirmed for the first time using fresh human corneal tissue. This finding may be useful in further biomechanical studies.

Evaluation of Biomechanically Corrected Intraocular Pressure Measurements in Keratoconus and Forme Fruste Keratoconus

2020 ◽  
Vol 63 (6) ◽  
pp. 541-549
Author(s):  
Tomoya Nishida ◽  
Takashi Kojima ◽  
Takahiro Kataoka ◽  
Naoki Isogai ◽  
Yoko Yoshida ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Biomechanical Properties ◽  
Control Group ◽  
Pressure Measurements ◽  
Altman Plot ◽  
Significant Difference ◽  
The Difference ◽  
The Right ◽  
Corneal Biomechanical Properties ◽  
Forme Fruste Keratoconus

<b><i>Introduction:</i></b> Although biomechanically corrected intraocular pressure (bIOP) is available, the effectiveness of intraocular pressure (IOP) correction in keratoconus and forme fruste keratoconus (FFK) eyes has not been investigated. <b><i>Objective:</i></b> Evaluation of bIOP measurements in eyes with keratoconus and FFK. <b><i>Methods:</i></b> Forty-two eyes in 21 patients with keratoconus in one eye and FFK in the fellow eye were examined (KC/FFK group; mean age 24.62 ± 8.6 years; 16 males and 5 females). The control group consisted of 62 eyes in 31 unaffected subjects (mean age 26.26 ± 3.64 years; 15 males and 16 females). The bIOP was determined using a Scheimpflug-based tonometer (Corvis Scheimpflug Technology [Corvis ST®]) after measuring the IOP with a conventional non-contact tonometer (NIOP). The agreement between NIOP and bIOP values was examined using the Bland-Altman plot. The difference between NIOP and bIOP (bIOP correction amount) was compared between keratoconus and FFK eyes. <b><i>Results:</i></b> In the control group, there were no significant differences between right and left eyes in both NIOP and bIOP values (<i>p</i> = 0.975 and <i>p</i> = 0.224, respectively). In the KC/FFK group, NIOP values were significantly lower in the keratoconus eyes (9.93 ± 1.96 mm Hg) than in the FFK eyes (12.23 ± 3.03 mm Hg; <i>p</i> = 0.0003). There was no significant difference in bIOP values between the right and left eyes of the KC/FFK group (<i>p</i> = 0.168). The bIOP correction amount was significantly increased in keratoconus eyes (3.58 ± 2.12 mm Hg) compared to in FFK eyes (1.80 ± 3.32 mm Hg; <i>p</i> = 0.011). <b><i>Conclusions:</i></b> For eyes with keratoconus and FFK, the bIOP method is effective to adjust IOP measurements based on corneal biomechanical properties.

scholarly journals Time-varying regularity of changes in biomechanical properties of the corneas after removal of anterior corneal tissue

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Di Zhang ◽  
Xiao Qin ◽  
Haixia Zhang ◽  
Lin Li
Keyword(s):  
Elastic Modulus ◽  
Stress Relaxation ◽  
Refractive Surgery ◽  
Biomechanical Properties ◽  
Collagen Fibrils ◽  
Uniaxial Tensile ◽  
Control Group ◽  
Corneal Tissue ◽  
Corneal Refractive Surgery ◽  
Corneal Biomechanical Properties

Abstract Background The corneal biomechanical properties with the prolongation of time after corneal refractive surgery are important for providing a mechanical basis for the occurrence of clinical phenomena such as iatrogenic keratectasia and refractive regression. The aim of this study was to explore the changes of corneal elastic modulus, and stress relaxation properties from the 6-month follow-up observations of rabbits after a removal of anterior corneal tissue in simulation to corneal refractive surgery. Methods The anterior corneal tissue, 6 mm in diameter and 30–50% of the original corneal thickness, the left eye of the rabbit was removed, and the right eye was kept as the control. The rabbits were normally raised and nursed for 6 months, during which corneal morphology data, and both of corneal hysteresis (CH) and corneal resistance factor (CRF) were gathered. Uniaxial tensile tests of corneal strips were performed at months 1, 3, and 6 from 7 animals, and corneal collagen fibrils were observed at months 1, 3, and 6 from 1 rabbit, respectively. Results Compared with the control group, there were statistical differences in the curvature radius at week 2 and month 3, and both CH and CRF at months 1, 2, and 6 in experiment group; there were statistical differences in elastic modulus at 1, 3, and month 6, and stress relaxation degree at month 3 in experiment group. The differences in corneal elastic modulus, stress relaxation degree and the total number of collagen fibrils between experiment and control groups varied gradually with time, and showed significant changes at the 3rd month after the treatment. Conclusions Corneas after a removal of anterior corneal tissue undergo dynamic changes in corneal morphology and biomechanical properties. The first 3 months after treatment could be a critical period. The variation of corneal biomechanical properties is worth considering in predicting corneal deformation after a removal of anterior corneal tissue.

Realistic hardening-to-softening transition effects of metals over the finite strain range up to failure

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zi-Han Xu ◽  
Lin Zhan ◽  
Si-Yu Wang ◽  
Hui-Feng Xi ◽  
Heng Xiao
Keyword(s):  
Finite Strain ◽  
Plastic Work ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Trial And Error ◽  
Content Type ◽  
Transition Effects ◽  
Iterative Procedures ◽  
First Time ◽  
Hardening And Softening

PurposeA new approach is proposed toward accurately matching any given realistic hardening and softening data from uniaxial tensile test up to failure and moreover, toward bypassing usual tedious implicit trial-and-error iterative procedures in identifying numerous unknown parameters.Design/methodology/approachFinite strain response features of metals with realistic hardening-to-softening transition effects up to eventual failure are studied for the first time based on the self-consistent elastoplastic J2-flow model with the logarithmic stress rate. As contrasted with usual approximate and incomplete treatments merely considering certain particular types of hardening effects such as power type hardening, here a novel and explicit approach is proposed to obtain a complete form of the plastic-work-dependent yield strength over the whole hardening and softening range.FindingsA new multi-axial evolution equation for both hardening and softening effects is established in an explicit form. Complete results for the purpose of model validation and prediction are presented for the finite strain responses of monotonic uniaxial stretching up to failure.Originality/valueNew finite strain elastoplastic equations are established with a new history-dependent variable equivalently in place of the usual plastic work. With these equations, a unified and accurate simulation of both gardening and softening effects up to failure is achieved for the first time in an explicit sense without involving usual tedious implicit trial-and-error iterative procedures.

Biomechanical and Elastographic Analysis of Mesenchymal Stromal Cell Treated Tissue Following Surgery

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Hazel Marie ◽  
Yong Zhang ◽  
Jeremy Heffner ◽  
Heath A. Dorion ◽  
Diana L. Fagan
Keyword(s):  
Mechanical Property ◽  
Tensile Test ◽  
Tensile Testing ◽  
Recovery Period ◽  
Strain Analysis ◽  
Biomechanical Properties ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Ongoing Research ◽  
Uniaxial Tensile Testing

Hernia repair continues to be a problem facing surgeons today, particularly because of the high incidence of reoccurrence. This work presents preliminary data of a pioneering effort to investigate the effect of mesenchymal stromal cells (MSCs) on mechanical property enhancement in full thickness fascial defects. Heparinized MSCs harvested from a rabbit’s tibia/iliac crest were applied to two fascial defects on the rabbit’s abdominal wall, with two other defects acting as controls (no MSCs added). After an 8 week recovery period, the entire abdominal fascia was harvested for mechanical property testing and elastographic strain analysis. Preliminary results from uniaxial tensile testing indicate a significant increase in the modulus of toughness strain energy, with at least a 50% increase in the MSC treated defects as compared with the control defects. Results from the elastographic strain analysis show excellent correlation in the calibration of the elastography to the uniaxial tensile test, with nearly identical moduli of elasticity. In addition, the elastographs clearly show tissue property heterogeneity at all stages of tensile testing. The MSC treated tissue demonstrates promise of enhanced material properties over that of the nontreated tissue; testing and analysis is ongoing. The elastography provides pixel-level description of tissue property variations providing critical information on wound healing effectiveness that would be impossible with other methods. In the ongoing research, optical elastography, in combination with the traditional tensile test and tissue histology, will be used to characterize localized biomechanical properties directly within the defect area and to locate “crack” initiation and propagation sights as the material is strained to rupture.

scholarly journals Meta-analysis of Corneal Biomechanical Effects after SMILE and FS-LASIK

2019 ◽  
Author(s):  
Jie Qin ◽  
Tingting Fu ◽  
Qi Tang ◽  
Lu Yang ◽  
Min Chen
Keyword(s):  
Meta Analysis ◽  
Corneal Biomechanics ◽  
Cochrane Library ◽  
Surgical Methods ◽  
Significant Difference ◽  
Newcastle Ottawa Scale ◽  
Lenticule Extraction ◽  
The Difference ◽  
The Cochrane Library ◽  
Chinese Group

Abstract Background: To evaluate and compare corneal biomechanics after treatment of myopia using small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK). Methods: We performed a meta-analysis and searched for reports concerning corneal biomechanics after SMILE and FS-LASIK using MEDLINE, EMbase, CNKI and the Cochrane Library. The analysis included corneal hysteresis (CH) and corneal resistance factor (CRF) before and 3 months after the surgery. The quality of the reports was evaluated using the Newcastle-Ottawa scale (NOS). Statistical analysis was performed using RevMan5. Results: Only six studies with a total of 771 eyes were ultimately included in this meta-analysis, and the random effects model was adopted. The preoperative and three-month postoperative CH and CRF of SMILE and FS-LASIK were compared by the meta-analysis. No statistically significant difference was found in CH or CRF between the SMILE group and the FS-LASIK group before the surgery (WMD，-0.12; 95% CI，-0.31～0.06; P，0.19; WMD，-0.05; 95% CI，-0.29～0.19; P，0.69). There was no statistically significant difference in CH between the two surgical methods 3 months after the operation in the foreign group (WMD，0.19; 95% CI，-1.02～1.41; P，0.75) or in the Chinese group (WMD，0.13; 95% CI，-0.16～0.41; P，0.75). Likewise, no statistically significant difference was found in CRF between the two surgical methods in the foreign group 3 months after the operation (WMD，-0.11; 95% CI，-2.53～-2.31; P，0.93). Nevertheless, the difference in CRF between the two surgical methods was statistically significant in the Chinese group (WMD，0.26; 95% CI，0.06～0.47; P，0.01). Concusion: This meta-analysis indicated that SMILE showed no significant postoperative advantage in CH in comparison with FS-LASIK. For CRF, SMILE exhibited no obvious postoperative advantage in comparison with FS-LASIK in the foreign group, whereas SMILE was superior to FS-LASIK in the Chinese group.

scholarly journals Impact of grafting type on Esca foliar symptoms

OENO One ◽  
2017 ◽  
Vol 51 (2) ◽  
Author(s):  
Séverine Mary ◽  
Coralie Laveau ◽  
Pascal Lecomte ◽  
Marc Birebent ◽  
Jean-Philippe Roby
Keyword(s):  
The Other ◽  
Lower Percentage ◽  
Cabernet Sauvignon ◽  
Climatic Regions ◽  
Foliar Symptoms ◽  
Significant Difference ◽  
The Difference ◽  
First Time

<p style="text-align: justify;"><strong>Aim:</strong> The aim of the survey was to investigate if the grafting type influences the foliar expression of Esca during summer.</p><p style="text-align: justify;"><strong>Methods and Results:</strong> Observations were conducted on plots distributed in two French winegrowing regions (two different climatic regions) with two varieties (Cabernet-Sauvignon in the Bordeaux region and Mourvèdre in Provence). Three grafting types were compared: Omega graft, Whip and Tongue graft, and full cleft graft. For both varieties, we found a significant effect of the type of grafting on the foliar development of Esca symptoms. Full cleft grafted plots showed a significantly lower percentage of Esca foliar symptoms than the other two modalities, which were not significantly different from one another. Concerning Omega grafted plots, a significant difference in the rate of Esca foliar symptoms was highlighted compared to full cleft grafted plots, with a higher rate on Omega grafted plots, but these plots were also younger.</p><p style="text-align: justify;"><strong>Conclusions:</strong> The study established, for the first time, the difference between full cleft field grafted plots and Omega and Whip and Tongue grafted plots, revealing a higher incidence of Esca on the latter types of grafting.</p><p style="text-align: justify;"><strong>Significance and impact of the study:</strong> The spread of mechanical graft could be one of the factors explaining the increasing incidence of Esca in vineyard.</p>

scholarly journals Prevalence of Dental Number Anomalies Among A Group of Turkish Children

2021 ◽  
Vol 25 (3) ◽  
pp. 153-158
Author(s):  
Burcu Güçyetmez Topal
Keyword(s):  
Tooth Agenesis ◽  
Supernumerary Teeth ◽  
Anterior Maxilla ◽  
Turkish Children ◽  
Appropriate Treatment ◽  
Significant Difference ◽  
The Difference ◽  
And Gender ◽  
Clinical Records ◽  
First Time

Summary Background/Aim: The study aimed to evaluate the prevalence and distribution of congenital dental number anomalies in the permanent dentition among a group of Turkish children in the Inner Aegean Region of Turkey. Material and Methods: A total of 5377 patients aged 7–9 who visited our clinic for the first time between September 2018 and September 2019 were investigated. The children were examined for tooth agenesis and supernumerary teeth using panoramic radiographs taken for various reasons and clinical records reviewed. Dental number anomalies were evaluated according to gender and localization. Descriptive and comparative statistical analyses were performed using the SPSS package software program Version 23. Results: For the study, the data of 1987 patients (947 female, 1040 male) were examined. The tooth agenesis was found in 109 patients (5.5%), the supernumerary teeth were found in 24 patients (1.2%). The prevalence of tooth agenesis was 5% in males, 6% in females. There was no statistical difference between genders (p>0.05). The distribution of tooth agenesis according to jaws and sides by gender was not statistically different (p>0.05). The most commonly missing teeth were mandibular left second premolar (37.6% of patients) and mandibular right second premolar (33% of patients). According to types of teeth and gender, molar tooth agenesis was seen more common in females than males (p<0.05), there was no significant difference in other types of teeth by gender. The prevalence of supernumerary teeth were 1.9% in males, 0.4% in females and the difference between genders was found to be statistically significant (p<0.05). All the supernumerary teeth were located in the anterior maxilla, and half of them were mesiodens. Conclusions: Early diagnosis and appropriate treatment choice are very important managing complications associated with congenital dental number anomalies and for differential diagnosis of characteristic syndromes.

Prospective one year study of corneal biomechanical changes following high intensity, accelerated cornea cross-linking in patients with keratoconus using a non-contact tonometer

2021 ◽  
pp. 112067212110697
Author(s):  
Mohammed Ziaei ◽  
Jinny J Yoon ◽  
Hans R Vellara ◽  
Akilesh Gokul ◽  
Jay J Meyer ◽  
...  
Keyword(s):  
High Intensity ◽  
High Speed ◽  
Biomechanical Properties ◽  
High Irradiance ◽  
Cross Linking ◽  
Continuous Exposure ◽  
Tertiary Referral Center ◽  
Significant Difference ◽  
Prospective Longitudinal ◽  
Corneal Biomechanical Properties

Purpose To characterize corneal biomechanical properties utilizing a dynamic ultra-high-speed Scheimpflug camera equipped with a non-contact tonometer (CorVis ST, CST) in keratoconic corneas following continuous high intensity, high irradiance corneal cross-linking. Design Prospective longitudinal single-centre study at a tertiary referral center. Methods Corneal biomechanical properties were measured in patients with progressive keratoconus undergoing high intensity (30 mW/cm2), high irradiance (5.4 J/cm2), accelerated corneal cross-linking with continuous exposure to ultraviolet-A for 4 min. CST was used to assess corneal biomechanical properties pre-operatively and at 1, 3, 6 and 12 months post-operatively. CST output videos were further analyzed using several previously reported algorithms. Results A total of 25 eyes of 25 participants were examined. The mean age of participants was 20.9 ± 5.3 years; 56% were male and 80% were of Māori or Pacific Island origin. Energy absorbed area (mN mm), was the only significantly changed parameter compared to baseline at all time points measuring 3.61 ± 1.19 preoperatively, 2.81 ± 1.15 at 1 month ( p = 0.037), 2.79 ± 0.81 ( p = 0.033) at 3 months, 2.76 ± 0.95 ( p = 0.028) at 6 months and 2.71 ± 1.18 ( p = 0.016) at 12 months. Conclusions The significant difference between the pre and post-operative energy absorbed area appears to reflect changes in corneal viscous properties that occur following corneal cross-linking.

Deqi Sensation Between the Acupuncture-Experienced and the Naïve: A Korean Study II

2005 ◽  
Vol 33 (02) ◽  
pp. 329-337 ◽  
Author(s):  
Jongbae Park ◽  
Hijoon Park ◽  
Hyangsook Lee ◽  
Sabina Lim ◽  
Kyooseok Ahn ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Informed Consent ◽  
Previous Experience ◽  
Acupuncture Sensation ◽  
Significant Difference ◽  
Korean Study ◽  
Future Treatments ◽  
The Difference ◽  
First Time ◽  
Intensity Dimension

Previous experience of acupuncture is believed to affect people's expectation of future treatments. Therefore, subjects who have had acupuncture are generally excluded from sham-controlled acupuncture clinical trials. However, this assumption has not been proven, but just accepted because of the lack of evidence to the contrary. To investigate the difference in frequency and intensity of acupuncture sensation between subjects who have had acupuncture and those who have not, 36 acupuncture-experienced subjects were invited to take part in the study. After informed consent was obtained, participants were asked to complete the acupuncture sensation scale (ASS) according to what they expected needling to feel like. The needling was done at the left Hegu (LI 4) point and consisted of insertion, stimulation for 30 seconds and removal. After needling, the subjects were asked to complete the same ASS according to what they actually experienced. Adverse events were monitored. The frequency of each sensation expected and experienced, as well as acupuncture sensation scores were compared. More than 60% of the subjects expected to feel sensations of penetrating (87.6% to 100%), aching (71.2% to 95.5%), tingling (87.6% to 100%), pricking (79.7% to 99.2%) and throbbing (64.2% to 91.4%). In fact, the subjects experienced sharp (60.9% to 89.1%), intense (60.9% to 89.1%), radiating (71.2% to 95.5%) and heavy (74.8% to 97.4%) sensations just as much. The subjects expected more hurting ( p =0.001), tingling ( p <0.001), pricking ( p =0.010), stinging ( p =0.012), burning ( p =0.001) and pulsing ( p =0.009) than they experienced, while more heaviness ( p =0.011) was experienced than expected. The same outcome measures were also compared between experienced and naïve groups. Apart from the fact that the acupuncture-experienced participants expected to feel pricking ( p =0.030) and stinging ( p =0.002), and experienced hurting ( p =0.022) and stinging ( p =0.028) significantly less than those who had not had acupuncture before, there was no significant difference between first time and experienced subjects. The results indicate that previous experience does not affect the people's expectation and does not hinder people from experiencing Deqi. In addition, a constellation of Deqi-related acupuncture-specific sensations is more than just a general pain intensity dimension, which requires a biochemical and physiological exploration.

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