Assessment of changes in the biomechanical properties of the cornea after FemtoLASIK surgery

2021 ◽  
pp. 121-125
Author(s):  
E.V. Boiko ◽  
◽  
E.S. Togo ◽  
I.B. Litvin ◽  
A.B. Kachanov ◽  
...  
Keyword(s):  
Key Words ◽  
Refractive Surgery ◽  
Biomechanical Properties ◽  
Corvis St ◽  
Vision Correction ◽  
Before And After ◽  
Keratorefractive Surgery

Purpose. The aim of the study is to investigate the biomechanical properties of the cornea before and after FemtoLASIK in patients with myopia. Material and methods. 24 patients (42 eyes) underwent refractive vision correction using the FemtoLASIK method. The Oculus CORVIS ST ® device (Oculus, Germany) was used to assess the biomechanical properties of the cornea. Results. A statistically significant decrease in the rigidity and strength of the cornea was noted after keratorefractive surgery. Conclusion. Refractive surgery using FemtoLASIK technology leads to a decrease in the rigidity of the cornea, and therefore to a reduction in its framework properties. Key words: refractive surgery, FemtoLASIK, myopia, laser correction, biomechanical properties of the cornea, Oculus CORVIS ST ®.

scholarly journals Investigation of corneal biomechanical properties using the CORVIS ST device (Oculus, Germany) in patients with myopia and myopic astigmatism

2020 ◽  
pp. 20-28
Author(s):  
V.D. Antonuk ◽  
◽  
T.S. Kuznetsova ◽  
Keyword(s):  
Excimer Laser ◽  
Refractive Surgery ◽  
Corneal Thickness ◽  
Biomechanical Properties ◽  
Corvis St ◽  
Vision Correction ◽  
Laser Vision ◽  
Laser Refractive Surgery ◽  
Myopic Astigmatism ◽  
Corneal Biomechanical Properties

Purpose. To evaluate the corneal biomechanical properties using the CORVIS ST device (Oculus, Germany) in patients with myopia and myopic astigmatism with intact cornea as well as in patients with myopia and myopic astigmatism who underwent excimer laser refractive surgery using femtolaser or microkeratome. Material and methods. Totally the study included 65 patients aged 18 years to 56 years with myopia and myopic astigmatism of various degrees were examined. They were scheduled for excimer laser refractive surgery after laser refractive surgery in different periods from 5 days to 5 years. Among the additional methods of examination, all patients were measured the biomechanical properties of the cornea using a CORVIS ST device (Oculus, Germany). Results. After excimer laser refractive surgery performing for myopia and myopic astigmatism correction, indicators of the corneal biomechanical properties, namely indicators describing stiffness and elasticity were changed, as well as IOP indicators. Conclusion. The biomechanical properties of the cornea, such as stiffness and elasticity, can be assessed using the CORVIS ST device (Oculus, Germany). After excimer laser vision correction of myopia and myopic astigmatism, corneal stiffness and elasticity decreases. IOP value in patients after excimer laser correction of myopia and myopic astigmatism decreases. It is associated with a decrease in corneal thickness but is not associated with a true decrease in IOP. Key words: biomechanical properties of the cornea, refractive surgery, excimer laser vision correction, femtolaser vision correction, myopia, myopic astigmatism.

scholarly journals Corneal Distortion and Corneal Morphological Parameters in Naïve Eyes Analyzed with a Scheimpflug Camera

2020 ◽  
Vol 3 (2) ◽  
pp. p22
Author(s):  
Sandro Sbrodone ◽  
Adele Ragucci ◽  
Gennarfrancesco Iaccarino ◽  
Domenico de Robertis ◽  
Giovan Battista Scazzi ◽  
...  
Keyword(s):  
Refractive Surgery ◽  
Corneal Thickness ◽  
Biomechanical Properties ◽  
Morphological Parameters ◽  
Corvis St ◽  
Iop Measurement ◽  
Biomechanical Evaluation ◽  
Spss Software ◽  
Biomechanical Features ◽  
Linear Regressions

Background: The study of the corneal biomechanical properties (CBP) is gaining always more interest, thanks to the applications to refractive surgery and to the overall management of several corneal diseases. Purpose: To analyze the eventual relationships between corneal distortion and morphologic features in healthy subjects. Methods: one eye of one hundred and fifty-two healthy participants, 87 women and 65 men, aging from 23 to 65 years old, were evaluated in this study. Every eye underwent a complete clinical examination, that included also a tomographic scan using Pentacam HR (Oculus, Wetzlar, Germany) and a biomechanical evaluation using Corvis ST (Oculus, Wetzlar, Germany). Linear regressions among refractive defect, corneal volume (CV), anterior corneal curvature and central corneal thickness (CCT) vs corneal biomechanical features provided by Corvis ST have been ran using SPSS software version 18.0. Results: Corneal distortion factors showed a low correlation both with corneal morphological parameters and with refractive defect. No significant correlations (p> 0.01) were found among morphologic and biomechanical features evaluated. Discussion: results observed in this study could help in recognize the healthy range of values of CBP parameters provided by CST. This information could be very useful in many ophthalmology topics such as the accurate IOP measurement, the early diagnosis of corneal degenerations, such as keratoconous, and the screening of subject undergoing refractive surgery. Conclusions: even if data of this study need to be confirmed in further ones with larger populations, results here observed suggest that Corvis ST is a device providing an evaluation of corneal distortion not influenced by morphological corneal factors. This information could help in better screening and managing the diseased corneas.

scholarly journals Effect of Mydriasis-Caused Intraocular Pressure Changes on Corneal Biomechanical Metrics

2021 ◽  
Vol 9 ◽  
Author(s):  
Yufeng Ye ◽  
Yi Li ◽  
Zehui Zhu ◽  
Anas Ziad Masoud Abu Said ◽  
Kevin Nguelemo Mayopa ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Disease Progression ◽  
Refractive Surgery ◽  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Medical Procedures ◽  
Corvis St ◽  
Before And After ◽  
The Mean ◽  
Pressure Changes

Purpose: To evaluate the dependence of biomechanical metrics on intraocular pressure (IOP).Methods: 233 refractive surgery patients were included in this study—all were examined 3 times with the Corvis ST before and after dilation, and the differences (∆) in the main device parameters were assessed. The data collected included the biomechanically corrected IOP (bIOP), the central corneal thickness (CCT), and six dynamic corneal response (DCR) parameters, namely DA, DARatio2mm, IIR, SP-A1, CBI, and SSI. Participants were divided into three groups according to the changes in patients’ bIOP after mydriasis.Results: Intra-operator repeatability was generally high in most of the DCR parameters obtained before and after dilation. The mean changes in bIOP and CCT after dilation were −0.12 ± 1.36 mmHg and 1.95 ± 5.23 μm, respectively. Only ∆DARatio2mm, ∆IIR, and ∆CBI exhibited a statistically significant correlation with ∆CCT (p < 0.05). The changes in all DCR parameters, especially ∆DA and ∆SP-A1 were also correlated with ∆bIOP (p < 0.01)—a 1-mmHg change in bIOP was associated, on average, with 5.612 and −0.037 units of change in SP-A1 and DA, respectively. In contrast, the weakest correlation with ∆bIOP was exhibited by ∆SSI.Conclusion: Most corneal DCR parameters, provided by the Corvis ST, were correlated with IOP, and more weakly with CCT. Changes experienced in CCT and IOP should therefore be considered in studies on corneal biomechanics and how it is affected by disease progression and surgical or medical procedures.

The influence of osteopathic correction on the rate of various rhythms of the body

2019 ◽  
pp. 64-71 ◽  
Author(s):  
A. E. Chernikova ◽  
Yu. P. Potekhina
Keyword(s):  
Heart Rate ◽  
Respiratory Rate ◽  
Age Groups ◽  
Biomechanical Properties ◽  
Dispersion Analysis ◽  
The Body ◽  
Body Tissues ◽  
Age Related ◽  
Significant Difference ◽  
Before And After

Introduction. An osteopathic examination determines the rate, the amplitude and the strength of the main rhythms (cardiac, respiratory and cranial). However, there are relatively few studies in the available literature dedicated to the influence of osteopathic correction (OC) on the characteristics of these rhythms.Goal of research — to study the influence of OC on the rate characteristics of various rhythms of the human body.Materials and methods. 88 adult osteopathic patients aged from 18 to 81 years were examined, among them 30 men and 58 women. All patients received general osteopathic examination. The rate of the cranial rhythm (RCR), respiratory rate (RR) heart rate (HR), the mobility of the nervous processes (MNP) and the connective tissue mobility (CTM) were assessed before and after the OC session.Results. Since age varied greatly in the examined group, a correlation analysis of age-related changes of the assessed rhythms was carried out. Only the CTM correlated with age (r=–0,28; p<0,05) in a statistically significant way. The rank dispersion analysis of Kruskal–Wallis also showed statistically significant difference in this indicator in different age groups (p=0,043). With the increase of years, the CTM decreases gradually. After the OC, the CTM, increased in a statistically significant way (p<0,0001). The RCR varied from 5 to 12 cycles/min in the examined group, which corresponded to the norm. After the OC, the RCR has increased in a statistically significant way (p<0,0001), the MNP has also increased (p<0,0001). The initial heart rate in the subjects varied from 56 to 94 beats/min, and in 15 % it exceeded the norm. After the OC the heart rate corresponded to the norm in all patients. The heart rate and the respiratory rate significantly decreased after the OC (р<0,0001).Conclusion. The described biorhythm changes after the OC session may be indicative of the improvement of the nervous regulation, of the normalization of the autonomic balance, of the improvement of the biomechanical properties of body tissues and of the increase of their mobility. The assessed parameters can be measured quickly without any additional equipment and can be used in order to study the results of the OC.

scholarly journals Biomechanical properties of the bone during implant placement

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ádám László Nagy ◽  
Zsolt Tóth ◽  
Tamás Tarjányi ◽  
Nándor Tamás Práger ◽  
Zoltán Lajos Baráth
Keyword(s):  
Bone Structure ◽  
Biomechanical Properties ◽  
Control Group ◽  
Dynamic Tests ◽  
Bone Model ◽  
Implant Placement ◽  
Significant Difference ◽  
Before And After ◽  
Group 2 ◽  
Post Hoc

Abstract Background In this research the biomechanical properties of a bone model was examined. Porcine ribs are used as experimental model. The objective of this research was to investigate and compare the biomechanical properties of the bone model before and after implant placement. Methods The bone samples were divided in three groups, Group 1 where ALL-ON-FOUR protocol was used during pre-drilling and placing the implants, Group 2 where ALL-ON-FOUR protocol was used during pre-drilling, and implants were not placed, and Group 3 consisting of intact bones served as a control group. Static and dynamic loading was applied for examining the model samples. Kruskal–Wallis statistical test and as a post-hoc test Mann–Whitney U test was performed to analyze experimental results. Results According to the results of the static loading, there was no significant difference between the implanted and original ribs, however, the toughness values of the bones decreased largely on account of predrilling the bones. The analysis of dynamic fatigue measurements by Kruskal–Wallis test showed significant differences between the intact and predrilled bones. Conclusion The pre-drilled bone was much weaker in both static and dynamic tests than the natural or implanted specimens. According to the results of the dynamic tests and after a certain loading cycle the implanted samples behaved the same way as the control samples, which suggests that implantation have stabilized the skeletal bone structure.

scholarly journals Impact on refractive surgery due to increasing use of personal protection equipment: Insights from EUROCOVCAT group

2021 ◽  
pp. 112067212110186
Author(s):  
Arthur B Cummings ◽  
Cian Gildea ◽  
Antoine P Brézin ◽  
Boris E Malyugin ◽  
Ozlem Evren Kemer ◽  
...  
Keyword(s):  
Refractive Surgery ◽  
Unmet Need ◽  
World Health ◽  
Eye Care ◽  
Personal Protection Equipment ◽  
Social Distancing ◽  
Vision Correction ◽  
Emerging Issues ◽  
Health Organization ◽  
Motivating Factor

Since the World Health Organization declared COVID-19 to be a pandemic on 11th March 2020, changes to social and sanitary practices have included significant issues in access and management of eye care during the COVID-19 pandemic. Additionally, the fear of loss, coupled with social distancing, lockdown, economic instability, and uncertainty, have led to a significant psychosocial impact that will have to be addressed. In the current COVID-19 pandemic, personal protective equipment such as face masks or face coverings have become a daily necessity. While “mass masking” along with hand hygiene and social distancing became more widespread, new issues began to emerge – particularly in those who wore spectacles as a means of vision correction. As we began to see routine patients again after the first lockdown had been lifted, many patients visited our clinics for refractive surgery consultations with a primary motivating factor of wanting spectacle independence due to the fogging of their spectacles as a result of wearing a mask. In this article, we report on new emerging issues in eye care due to the widespread use of masks and on the new unmet need in the corneal and cataract refractive surgery fields.

Impact of Canada's Pacific Salmon Fleet Control Program

1979 ◽  
Vol 36 (7) ◽  
pp. 764-769 ◽  
Author(s):  
Peter H. Pearse ◽  
James E. Wilen
Keyword(s):  
Key Words ◽  
Statistical Data ◽  
Pacific Salmon ◽  
Control Program ◽  
Resource Rent ◽  
The Real ◽  
Before And After ◽  
Salmon Fishery

The available statistical data are analyzed to appraise the success of Canada's Pacific salmon fleet rationalization program, in terms of the extent to which it has prevented fishing costs from rising in pace with the value of the catch. It is found that while the fleet's revenues increased at about the same rate before and after the scheme was introduced in 1969, the real capital employed increased more slowly under the controls than earlier. The program has, nevertheless, failed in its purpose of preventing further expansion of redundant capital in the fleet. The reasons for this failure, and for certain apparent shifts in the structure of the fleet, are discussed. Key words: Pacific salmon fishery, capitalization, economic rationalization, resource rent

scholarly journals Novel Method of Measuring Corneal Viscoelasticity Using the Corvis ST Tonometer

2022 ◽  
Vol 11 (1) ◽  
pp. 261
Author(s):  
Agnieszka Boszczyk ◽  
Henryk Kasprzak ◽  
Joanna Przeździecka-Dołyk
Keyword(s):  
Intraocular Pressure ◽  
Viscoelastic Properties ◽  
High Speed ◽  
Central Area ◽  
Biomechanical Properties ◽  
P Value ◽  
Corvis St ◽  
Corneal Deformation ◽  
The Times ◽  
High Repeatability

Background: The process of rapid propagation of the corneal deformation in air puff tonometer depends not only on intraocular pressure, but also on the biomechanical properties of the cornea and anterior eye. One of the biomechanical properties of the cornea is viscoelasticity, which is the most visible in its high-speed deformations. It seems reasonable to link the corneal viscoelasticity parameter to two moments of the highest speed of corneal deformations, when the cornea buckles. The aim of this work is to present a method of determining the time and place of occurrence of corneal buckling, examine spatial and temporal dependencies between two corneal applanations and bucklings in the Corvis ST tonometer, and correlate these dependencies with corneal viscoelastic properties. Methods: Images of the horizontal cross section of the Corvis ST deformed cornea from the air puff tonometer Corvis ST were used. 14 volunteers participated in the study, each of them had one eye measured eight times. Mutual changes in the profile slopes of the deformed corneas were numerically determined. They describe pure corneal deformation, eliminating the influence of rotation, and displacement of the entire eyeball. For each point in the central area of the corneal profile, the maximum velocities of mutual slope changes accompanying the applanations were estimated. The times of their occurrence were adopted as buckling times. Results: The propagation of buckling along the corneal profile is presented, as well as the repeatability and mutual correlations between the buckling parameters and intraocular pressure. Based on the relationship between them, a new parameter describing corneal hysteresis: Corvis Viscoelasticity (CVE) is introduced. It is characterized by high repeatability: ICC = 0.82 (0.69–0.93 CI) and low and insignificant correlation with intraocular pressure: r = 0.25 (p-value = 0.38). Conclusion: The results show for the first time how to measure the corneal buckling and viscoelastic effects with Corvis ST. CVE is a new proposed biomechanical parameter related to the viscoelastic properties of the cornea, which has high repeatability for the examined subject. The distribution of its values is planned to be tested on different groups of patients in order to investigate its clinical applicability.

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