\r\n\tAll book chapters are produced by forward-thinking specialists in the area of renewable energy and smart grids, with detailed analysis and/or case studies. This book is intended to serve as a reference for graduate students, academics, professionals, and system operators.
",isbn:"978-1-83881-907-1",printIsbn:"978-1-83881-906-4",pdfIsbn:"978-1-83881-909-5",doi:null,price:0,priceEur:0,priceUsd:0,slug:null,numberOfPages:0,isOpenForSubmission:!1,hash:"42f44a6c474bb1bb3664945884ff1879",bookSignature:"Prof. Wenping Cao and Dr. Shubo Hu",publishedDate:null,coverURL:"https://cdn.intechopen.com/books/images_new/10498.jpg",keywords:"Wind Speed, Wind Farm Design, Wind Energy Prediction, Power Dispatch, Optimization Algorithms, Stability Analysis, Distributed Generation, Integrated Energy System, Market Mechanism, Demand Side Management, Data-Driven Method, Electric Grid Security",numberOfDownloads:39,numberOfWosCitations:0,numberOfCrossrefCitations:0,numberOfDimensionsCitations:0,numberOfTotalCitations:0,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"June 1st 2020",dateEndSecondStepPublish:"June 22nd 2020",dateEndThirdStepPublish:"August 21st 2020",dateEndFourthStepPublish:"November 9th 2020",dateEndFifthStepPublish:"January 8th 2021",remainingDaysToSecondStep:"7 months",secondStepPassed:!0,currentStepOfPublishingProcess:5,editedByType:null,kuFlag:!1,biosketch:"A Chair Professor of Electrical Power Engineering at the Aston University, UK, and a Marie Curie Fellow at the Massachusetts Institute of Technology, USA.",coeditorOneBiosketch:null,coeditorTwoBiosketch:null,coeditorThreeBiosketch:null,coeditorFourBiosketch:null,coeditorFiveBiosketch:null,editors:[{id:"174154",title:"Prof.",name:"Wenping",middleName:null,surname:"Cao",slug:"wenping-cao",fullName:"Wenping Cao",profilePictureURL:"https://mts.intechopen.com/storage/users/174154/images/system/174154.jpg",biography:"Dr. Wen-Ping Cao received the B.Eng degree in electrical engineering from Beijing Jiaotong University, Beijing, China, in 1991, and the Ph.D. degree in electrical machines and drives from the University of Nottingham, Nottingham, UK, in 2004. 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\n
1. Introduction
\n
The availability and use of electrical power in the society is crucial in the development and growth of the society. Power generated from power stations is transmitted using high voltage transmission lines. The transmission of power from the point of generation to the point of use requires complex network of high voltage lines, systems and components [1]. High voltage conductors are usually subjected to vibration and the vulnerabilities of the power lines to vibration can lead to fatigue failure. Thus, power loading determination and control on the power grid can influence the integrity of the transmission network. High voltage conductor vibration is very difficult to model due to the fact that the responses exhibit a non-linear behaviour. There has been concerted effort to try and predict the conductor response as a result of aeolian vibration. Evaluations of conductor vibration caused by aeolian forces have been investigated be several researchers [2, 3, 4, 5, 6].
\n
Recent researches developed models to investigate wind-induced vibration using nonlinear time history, expert systems, the concept of principal modes, aero-elastic and bending stiffness [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]. The investigation of vortex formation and the phenomenon of wind-induced vibration was done using the concept fluid–solid dynamic excitation [18, 19, 20]. The models were used to determine how wind loading influenced the oscillation of transmission lines. This form of investigation was done by experimental studies carried out in a wind tunnel [21, 22]. The outcomes of these experiments were used to determine conductor input loading. Several models developed by various researchers can be used to determine conductor damping and also the placement of vibration absorbers on the line conductors to curtail the effect of cable mechanical oscillation [23, 24, 25, 26, 27]. Based on the various models that have been developed by researchers as indicated in the first and second paragraphs, there is a need to further analyze wind-induced vibration using finite element method (FEM) in MATLAB.
\n
The design, construction and maintenance of power transmission network requires adequate understanding of the system dynamics that occurs when subjected to vortex induced vibration [28]. Various analysis can be conducted using techniques that suit certain objectives. System integrity in high voltage transmission lines is of paramount importance. MATLAB is a multi-model simulation environment used for numerical computing. It can be integrated with physical hardware or systems in order to determine real-time performance, characteristics and behavior. MATLAB also provides a platform for special hardware in loop simulations [29]. These functionalities amongst others are vital in determining various characteristics and behaviors in high voltage transmission lines.
\n
High voltage transmission lines and grid can experience vulnerabilities such as vibration, electromagnetic transients, fatigue, transmission loss, switching surges, conductor sag fluctuation [30, 31]. When the conductor experiences vibration, the transmission lines experience high amplitudes of vibrations from wind forces and can lead to fatigue of the transmission lines [1]. The use of systems simulation and analysis provides the platform to understand the response of the transmission conductor. The responses considered in the chapter include transmission line excitation through wind loading, conductor properties such as damping and damper placement used in mitigating the vibration.
\n
The chapter discussed the development and implementation of a wind-induced high voltage transmission line vibration using finite element method (FEM) in MATLAB. The sections in the chapter discussed the development of transmission line equation of motion, the solution to the equation of motion, free and forced vibration of the transmission line, dampers and conductor self-damping, FEM MATLAB setup and implementation, simulation of FEM models. The chapter also discussed results from FEM models, simulation and experimental investigation. The chapter is focused towards the development of a finite element method and its implementation on the MATLAB software. The developed finite element method (FEM) was based on the concept of the simply supported beam model and it was used in modeling the transverse vibration of power line conductors. The results from the FEM were then compared with results from the analytical model and results obtained from experimental studies documented in [1]. The results from MATLAB simulations from the finite element models and experimental results were compared in order to determine the accuracy of the models. The developed FEM was then used as the means to verify the effect of varying the conductor axial tension on the natural frequencies of the conductors.
\n
\n
\n
2. Transmission line equation of motion (EOM)
\n
The transverse displacement of high voltage transmission line conductor is generally caused by wind loading. This form of vibration with small displacement is known as aeolian vibration and it is a source of concern to the power lines reliability. One the vulnerabilities is that it can cause fatigue failure of the transmission lines. Conductors are example of continuous or distributed systems and modeling its mechanical vibration can either be as a beam or taut string. In [18, 19], it was ascertained that modeling a conductor as a beam is more accurate than modeling it as a taut string due to the effect of the bending stiffness. Hence, in line with the above, the conductor transverse vibration was modeled as a beam, simply supported or pinned at both ends. The distributed loading on the conductor is replaced by effective point load that can effectively have the same resultant effect as that of the actual distributed load.
\n
The high voltage transmission line equation of motion was formulated by assuming that power conductors can modeled as beams with fixed ends. The following assumptions were considered [1]:
The power conductor is uniform along its length and it is slender
The power conductor is a solid with cylindrical body having both linear and homogeneous physical properties throughout its cross-sectional area
The power conductor has a symmetrical plane which acts as the plane of vibration such that there is the decoupling of translational and rotational motion.
\n\n
The assumptions were based on beam theory. In considering the power conductor as a beam, sagged by a tensile force \n\nS\n\n, being acted upon by a concentrated wind load \n\nf\n\nx\nt\n\n\n, with cross-sectional area \n\nA\n\n, density \n\nρ\n\n, flexural rigidity \n\nEI\n\n, displaced at a distance of \n\nx\n\n after time. In Eq. (1), the high voltage transmission line equation of motion is expressed as:
In order to derive a possible solution, the model was simplified using dimensionless functions and Dirac delta functions. In Eqs. (7)–(12), the variables are expressed in dimensionless form and expressed as:
Where \n\nγ\n\n represents the power conductor weight per unit length and \n\ng\n\n represents gravitational constant. \n\n\nX\nn\n\nδ\n\n\nX\n−\n\nX\nn\n\n\n\n\n represents the Dirac delta function, \n\nF\n\nX\nτ\n\n\n denotes the net transverse force per unit length acting on the conductor and \n\n\nF\nn\n\n\nτ\n\n\n denotes the nth concentrated force acting transversely on the conductor.
\n
\n
\n
3. Solution to the EOM
\n
The general solution to the high voltage transmission line equation of motion was derived using Euler-Bernoulli equation. The particular solution to the equation of motion was derived using a product of two functions. The two functions were first separated using the principle of variable separation as expressed in Eq. (14) [19]:
\n
\n\nY\n\nx\nt\n\n=\nX\n\nx\n\nT\n\nt\n\n\nE14
\n
Where \n\nX\n\nx\n\n\n is the normalized function representing the mode shape of the equation of motion. The normalized function ensures that orthogonality condition was satisfied in the derivation of the EOM model solution. Applying the normalized function in the EOM yields Eqs. (15) and (16):
Where \n\n\nX\n\n////\n\n\n\nx\n\n=\n\n\n\nd\n4\n\ny\n\n\ndx\n4\n\n\n\n, \n\n\nX\n\n//\n\n\n\nx\n\n=\n\n\n\nd\n2\n\ny\n\n\ndx\n2\n\n\n\n, \n\n\nT\n¨\n\n\nt\n\n=\n\n\n\nd\n2\n\ny\n\n\ndt\n2\n\n\n\n and \n\n\nω\n2\n\n\n is a constant that equates \n\nx\n\n and \n\nt\n\n. Assuming that \n\nX\n\nx\n\n=\n\nZe\n\nΨ\nx\n\n\n\n, the model is expressed in Eq. (17) as:
Considering that \n\n\nZe\n\nΨ\nx\n\n\n≠\n0\n\n, hence \n\n\n\nEI\n\nΨ\n4\n\n−\nS\n\nΨ\n2\n\n+\nρA\n\nω\n2\n\n\n\n=\n0\n\n. The general solution of the Euler-Bernoulli equation which represents the solution to the equation of the motion of the transmission line is expressed in Eqs. (18) and (19) as [9]:
The values of \n\nΩ\n\n and \n\nΨ\n\n represents the general solution of the equation of motion. The practical implication of the derived solution is that it represents the transverse vibration of the high voltage transmission line. The derived solution has infinite number of solutions and the solution is indexed to accommodate all the possible solutions from the model. The indexed solution is expressed in Eqs. (20) and (21) as:
Where \n\n\nω\nn\n\n=\n2\nπ\n\nf\nn\n\n\n and for \n\nn\n=\n1\n,\n2\n,\n3\n,\n…\n\n.
\n
In Eqs. (22)–(24), the infinite natural frequencies of the power conductor were derived while considering that the mode shape is the same as a pinned-pinned beam eigenfunction model with no external force. Hence,
The self-damping model of the power conductor provided the basis to analyze free vibration experienced by the conductor. Free vibration occurs when the forcing function causing the power conductor to vibrate become zero. Hence the equation of motion is expressed in Eq. (28) as [19]:
Considering that the vibration model represents a multi-degree vibration system. The natural frequency of the power conductor is determined and expressed in Eqs. (34) and (35):
High voltage transmission lines are exposed to loading from the wind. The actual system representation through system simulation strategy considers a case of distributed load through the span of the conductor. In order to simplify simulations, the external force acting on the conductor is represented as a point load. In Eqs. (41)–(43), the equation of motion is solved with an excitation force in order to evaluate the actual response of high voltage transmission lines under aeolian vibration [1]. Hence,
The influence of external and internal damping mechanisms was considered in the conductor vibration model. The factors considered included the following [1, 32]:
The power conductor inter-strand motion and fluid damping. This is proportional to the conductor velocity and represented as viscous damping in the model.
The rate of strain in the power conductor. This proportional to the internal damping of the power conductor.
\n\n
The high voltage transmission line damped model is expressed in Eq. (48) as:
Where \n\nC\n\n and \n\nβ\n\n represent damping constants. In the presence of axial load, viscous air damping, strain rate damping or Kelvin-Voigt damping, high voltage transmission line integrity can be managed.
\n
There are various types of dampers that can be used to reduce vibration. The dampers are excited by the vibration of the power conductor and the vibration of their masses connected by the massager cable help to damp out energy. Stockbridge dampers are commonly installed on high voltage transmission lines to reduce aeolian vibrations. Stockbridge dampers can be symmetrical or asymmetrical in their design. An example of dampers installed on high voltage transmission lines is shown in \nFigure 1\n. The design of Stockbridge dampers follows the principle of cantilever beams with mass at the free ends. The contribution of dampers to power conductor vibration mitigation is to lower the severity of the vibration to a level that might prevent failure to the line.
\n
Figure 1.
Asymmetrical damper.
\n
\n
\n
7. FEM MATLAB model setup, formulation and implementation
\n
In order to implement the conductor model in MATLAB environment, finite element analysis formulation was done as function of the physical state of power transmission line conductor. The models developed using finite element analysis can then be implemented in MATLAB. The FEM model enables the analysis of the dynamic behavior and response of power line conductor to the dynamic forces of wind [33]. Consider a power transmission line subjected to dynamic aeolian vibration as an assembly of thin strands having distributed mass and elasticity. The physical model can be represented used partial differential equations. Each strand in the transmission line experiences axial, bending and torsional loads from the wind [34, 35]. The accurate representation of each factor is critical in the determination of the dynamic behavior of power transmission lines [36, 37]. Euler-Bernoulli curved beam theory was used to formulate the finite element model of power transmission lines.
\n
Consider a power transmission line experiencing a vertical force, curvature and an axial force has an axial displacement modeled in Eq. (49) as [21]:
Where \n\n\nθ\nx\n\n\n represents the rotation of the power line due to flexural effect, \n\nR\n\n represents the radius of rotation, \n\ny\n\n represents the distance from the axis of rotation to the centroidal axis of the conductor or transverse displacement, \n\nv\n\n represents tangential displacement and \n\nu\n\nx\n\n\n represents the axial displacement of the power lines. The shape function for power transmission lines having rotation, bending and axial motion components is modeled using discretization techniques and represented in Eqs. (50)–(52) as:
The power line matrix model contains the strand stiffness \n\nK\n\n, mass matrix \n\nM\n\n and the load vector \n\nF\n\n. They are expressed in Eq. (60) as:
Where \n\nA\n\n represents the cross-sectional area of the power line, \n\nE\n\n represents the young modulus of the power line material, \n\nI\n\n represents polar moment of area, \n\nT\n\n represents the kinetic energy of the system. The matrix is modeled in Eq. (61).
The finite element analysis follows a step by step numerical computation in the MATLAB environment as documented in [38, 39]. The dynamic response analysis assumes continuous displacement, velocity and acceleration [40, 41]. The numerical integration technique utilized was based on Newmark integration method. The compact form of the high voltage transmission line model is expressed in Eqs. (64)–(69) as [18]:
In order to test the validity of the models discussed earlier using MATLAB, an aluminum power conductor with a steel core having a total diameter of 35.56 mm and having an ultimate tensile strength of 51.51kN was used in setting up the MATLAB simulation. Further physical properties of the power cable are shown in \nTable 1\n. The power conductor had a minimum bending stiffness \n\n\nEI\nmin\n\n\n of 8.66 Nm2 and maximum bending stiffness \n\n\nEI\nmax\n\n\n of 433 Nm2. The wholistic finite element models where implemented in MATLAB using strategy expressed in \nFigure 2\n.
\n
\n
\n
\n
\n
\n
\n
\n\n
\n
Strand layer
\n
Strand material
\n
Diameter (mm)
\n
No. of strands
\n
Pitch per length (cm)
\n
Lay direction
\n
\n\n\n
\n
Layer 0
\n
Steel
\n
2.25
\n
1
\n
\n
\n
\n
\n
Layer 1
\n
Aluminum
\n
3.38
\n
6
\n
16.1
\n
Left hand lay
\n
\n
\n
Layer 2
\n
Aluminum
\n
3.38
\n
12
\n
22.2
\n
Right hand lay
\n
\n\n
Table 1.
Power transmission conductor physical properties.
\n
Figure 2.
FEM MATLAB implementation strategy.
\n
The inputs in the MATLAB algorithm were bending and axial loads, the cross-sectional area of the power conductor, strand radius and strand material type. The type of analysis which can be either static or dynamic was also specified as part initial and boundary conditions. Also included in the algorithm was to specify if the computation focuses on local vibration of the power conductor or the global vibration model.
\n
\n
\n
9. Experimental investigation of conductor vibration
\n
MATLAB code was written for the FEM and this was used to model the dynamic analysis of the problem of conductor vibration. To validate the FEM model an experimental study was conducted at the Vibration and Research Testing Centre (VRTC) situated at the University of KwaZulu-Natal which comprises of apparatus similar to that shown in \nFigure 3\n. The sweep tests (resonance search) were carried out and the test results were used to obtain natural frequencies and the modes of vibration for a Pelican conductor. The frequency range for the Pelican conductor was between 5 and 50 Hz and testing was done for three axial tensions of 20, 25, 30 and 35% of its ultimate tensile strength (UTS). The experimental results obtained were used to validate the developed FEM model. The comparison between results from the experimental data, FEM and the theoretical model for the three different axial tensions for high voltage conductors are reported in the next section.
\n
Figure 3.
Experimental test set-up [7] .
\n
\n
\n
10. Simulation and experimental results
\n
The results from the MATLAB simulations were compared with results from the finite element models (FEM) and experimental recordings. These are shown in \nFigures 4\n–\n7\n. The results were compared in terms of the natural frequency of vibration or vertical displacement of the power conductor.
\n
Figure 4.
Frequency of vibration at 20% UTS.
\n
Figure 5.
Frequency of vibration at 25% UTS.
\n
Figure 6.
Frequency of vibration at 30% of UTS.
\n
Figure 7.
Frequency of vibration at 35% of UTS.
\n
\n
\n
11. Conclusion
\n
The results showed that the implementation of the derived models in MATLAB provided a reliable strategy in the determination of the wind-induced dynamic properties of high voltage transmission lines. The results from MATLAB simulation, finite element method and experimental recordings were similar in values and showed similar trend. MATLAB as an environment can be used as a reliable simulation tool to implement and analyze high voltage conductor dynamics. The parameters obtained from the results, to some degree of accuracy can be used to predict the response of conductors due to aeolian vibration caused by wind loading.
\n
\n\n',keywords:"aeolian vibration, power conductor damping, resonant frequency, MATLAB",chapterPDFUrl:"https://cdn.intechopen.com/pdfs/60036.pdf",chapterXML:"https://mts.intechopen.com/source/xml/60036.xml",downloadPdfUrl:"/chapter/pdf-download/60036",previewPdfUrl:"/chapter/pdf-preview/60036",totalDownloads:647,totalViews:250,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,dateSubmitted:"September 6th 2017",dateReviewed:"February 11th 2018",datePrePublished:null,datePublished:"September 19th 2018",dateFinished:null,readingETA:"0",abstract:"Wind-induced vibration affects the performance and structural integrity of high voltage transmission lines. The finite element method (FEM) is employed to investigate wind-induced vibration in MATLAB. First, the FEM model was used to develop the equation of motion of the power line conductor. In addition, dampers, conditions for damping, free and forced vibrations of the overhead conductor were considered in the FEM model. Wind-induced experiments were conducted in the laboratory using an actual overhead power conductor. The developed FEM models were simulated in the MATLAB computing environment. The results from the MATLAB simulation, finite element and experimental recordings were compared in order to evaluate the efficacy of models simulated in MATLAB and developed using the FEM.",reviewType:"peer-reviewed",bibtexUrl:"/chapter/bibtex/60036",risUrl:"/chapter/ris/60036",book:{slug:"matlab-professional-applications-in-power-system"},signatures:"Chiemela Onunka and Evans Eshiemogie Ojo",authors:[{id:"221216",title:"Dr.",name:"Chiemela",middleName:null,surname:"Onunka",fullName:"Chiemela Onunka",slug:"chiemela-onunka",email:"connadoz@gmail.com",position:null,institution:{name:"Mangosuthu University of Technology",institutionURL:null,country:{name:"South Africa"}}},{id:"235240",title:"Mr.",name:"Evans E",middleName:null,surname:"Ojo",fullName:"Evans E Ojo",slug:"evans-e-ojo",email:"evanso@dut.ac.za",position:null,institution:null}],sections:[{id:"sec_1",title:"1. Introduction",level:"1"},{id:"sec_2",title:"2. Transmission line equation of motion (EOM)",level:"1"},{id:"sec_3",title:"3. Solution to the EOM",level:"1"},{id:"sec_4",title:"4. Free vibration of power conductor",level:"1"},{id:"sec_5",title:"5. Forced vibration of power conductor",level:"1"},{id:"sec_6",title:"6. Conductor self-damping and dampers",level:"1"},{id:"sec_7",title:"7. FEM MATLAB model setup, formulation and implementation",level:"1"},{id:"sec_8",title:"8. FEM MATLAB model implementation strategy",level:"1"},{id:"sec_9",title:"9. Experimental investigation of conductor vibration",level:"1"},{id:"sec_10",title:"10. Simulation and experimental results",level:"1"},{id:"sec_11",title:"11. Conclusion",level:"1"}],chapterReferences:[{id:"B1",body:'\nOjo EE. Dynamic characteristics of bare conductors [thesis]. Durban: University of KwaZulu-Natal; 2011\n'},{id:"B2",body:'\nGuerard S, Godard B, Lilien J-L. Aeolian vibrations on power-line conductors, evaluations of actual self-damping. IEEE Transactions on Power Delivery. 2011;26(4):2118-2122\n'},{id:"B3",body:'\nGodard B, Guerard S, Lilien J-L. Original real-time observations of aeolian vibrations on power-line conductors. IEEE Transactions on Power Delivery. 2011;26(4):2111-2117\n'},{id:"B4",body:'\nZhao L, Huang X. Integrated condition monitoring system of transmission lines based on fiber bragg grating sensor. In: Proceedings of the 2016 International Conference on Condition Monitoring and Diagnosis. 25-28 September, 2016; China, Xi?an: IEEE; 2016. p. 667-670\n'},{id:"B5",body:'\nLalonde S, Guilbault R, Langlois S. Numerical analysis of ACSR conductor-clamp systems undergoing wind-induced cyclic loads. IEEE Transactions on Power Delivery. 2017;99:1-9\n'},{id:"B6",body:'\nLu ML, Chan JK. Rational design equations for the aeolian vibration of overhead power lines. In: Proceedings of 2015 IEEE Power & Energy General Meeting. 26–30 July, 2015; USA, Denver: IEEE; 2015. p. 1-5\n'},{id:"B7",body:'\nLanglois S, Legeron FLF. Time history modelling of vibrations on overhead conductors with variable bending stiffness. IEEE Transactions on Power Delivery. 2014;29(2):607–614\n'},{id:"B8",body:'\nLanglois S, Legeron F. Prediction of aeolian vibration on transmission-line conductors using a nonlinear time history model – Part I: Damper model. IEEE Transaction on Power Delivery. 2014;29(2):1168-1175\n'},{id:"B9",body:'\nLanglois S, Legeron F. Prediction of aeolian vibration on transmission-line conductors using a nonlinear time history model – Part II: Conductor and damper model. IEEE Transaction on Power Delivery. 2014;29(3):1176-1183\n'},{id:"B10",body:'\nClaren R, Diana G. Mathematical analysis of transmission line vibration. IEEE Transactions on Power Apparatus And Systems. 1969;12:1741-1771\n'},{id:"B11",body:'\nHathout I, Callery-Broomfield K, Tang TT-T. Fuzzy probabilistic expert system for overhead conductor assessment and replacement. In: Proceedings of the 2015 IEEE Power & Energy Society General Meeting. 26–30 July, 2015; USA, Denver: IEEE; 2015. p.20-25\n'},{id:"B12",body:'\nLevesque F, Goudreau S, Langlois S, Legeron F. Experimental study of dynamic bending stiffness of ACSR overhead conductors. IEEE Transactions on Power Delivery. 2015;30(5):2252-2259\n'},{id:"B13",body:'\nAlminhana F, Mason M, Albermani F. A compact nonlinear dynamic analysis technique for transmission line cascades. Engineering Structures. 2018;158:164-174\n'},{id:"B14",body:'\nEl Damatty A, Elawady A. Critical load cases for lattice transmission line structures subjected to downbursts: Economic implications for design of transmission lines. Engineering Structures. 2018;159:213-226\n'},{id:"B15",body:'\nBarbieri N, Calado MKT, Mannala MJ, de Lima KY, Barbieri GSV. Dynamical analysis of various transmission line cables. Procedia Engineering. 2017;199:516-521\n'},{id:"B16",body:'\nYin X, Wu W, Li H, Zhong K. Vibration transmission within beam-stiffened plate structures using dynamic stiffness method. Procedia Engineering. 2017;199:411-416\n'},{id:"B17",body:'\nXie Q, Cai Y, Xue S. Wind-induced vibration of UHV transmission tower line system: Wind tunnel test on aero-elastic model. Journal of Wind Engineering & Industrial Aerodynamics. 2017;171:219-229\n'},{id:"B18",body:'\nDiana G, Falco M. On the forces transmitted to a vibrating cylinder by a blowing fluid. Meccanica. 1971;6:9-22\n'},{id:"B19",body:'\nCigrè Study Committee 22-Working Group 01. Report on aeolian vibration. Electra. 1989;1(124):101\n'},{id:"B20",body:'\nRawlins C.B. Model of power imparted to a vibrating conductor by turbulent wind [Report No. 93-83-3]. Spartanburg, South Carolina: Alcoa Conductor Products Company; 1983\n'},{id:"B21",body:'\nDeng HZ, Xu HJ, Duan CY, Jin XH, Wang ZH. Experimental and numerical study on the responses of a transmission tower to skew incident winds. Journal of Wind Engineering & Industrial Aerodynamics. 2016;157:171-188\n'},{id:"B22",body:'\nGhabraei S, Moradi H, Vossoughi G. Finite time-Lyapunov based approach for robust adaptive control of wind-induced oscillations in power transmission lines. Journal of Sound and Vibration. 2016;371:19-34\n'},{id:"B23",body:'\nEPRI. Transmission line reference book: Wind-induced conductor motion. Electrical Power Research Institute. Palo Alto, USA: EPRI; 1979\n'},{id:"B24",body:'\nEPRI. Transmission line reference book: Wind-induced conductor motion final report. Palo Alto, USA: EPRI; 2016\n'},{id:"B25",body:'\nVecchiarelli J, Currie I, Havard D. Computational analysis of aeolian conductor vibration with a stockbridge-type damper. Journal of Fluids and Structures. 2000;14:489-509\n'},{id:"B26",body:'\nHong K-J, Der Kiureghian A, Sackman JL. Mint: Bending behavior of helically wrapped cables. Journal of Engineering Mechanics. 2005;131(5):500\n'},{id:"B27",body:'\nGizaw M, Davidson IE, Loubser R, Bright G, Stephen R. Analyses of the vibration level of an OPGW at catenary value of 2100 m with multi-response Stockbridge dampers. In: Proceedings of the 2016 IEEE PES Power Africa Conference. June 28–July 2, 2016, Zambia, Livingstone: IEEE; 2016. p. 107-111\n'},{id:"B28",body:'\nXiao S, Wang H, Ling L. Research on a novel maintenance robot for power transmission lines. In: Proceedings of 4th International Conference on Applied Robotics for the Power Industry. 11–13 October, 2016; China, Jinan: IEEE; 2016. p. 1-6\n'},{id:"B29",body:'\nMathworks. MATLAB. The Mathworks Inc. 2017. [Online]. Available from: https://www.mathworks.com/products/matlab.html. [Accessed: Nov 11, 2017]\n'},{id:"B30",body:'\nXie T, Peng Z, Zhou Z. Study on optimization of anti-corona properties of 330-kv dampers. IEEE Transactions on Power Delivery. 2015;30(4):1827-1832\n'},{id:"B31",body:'\nLalonde S, Guilbault R, Langlois S. Modelling multilayered wire strands, a strategy based on 3D finte element beam-to-beam contacts – Part II: Application to wind-induced vibration and fatigue analysis of overhead conductors. International Journal of Mechanical Sciences. 2017;126:297-307\n'},{id:"B32",body:'\nHardy C. Analysis of self-damping characteristics of stranded cables in transverse vibration. In: Proceedings of CSME Mechanical Engineering Forum. 3–9 June, 1990; Canada, Toronto: CSME; 1990. p. 117-122\n'},{id:"B33",body:'\nOjo EE, Ijumba NM. Mint: Numerical method for evaluating the dynamic behaviour of power line conductors: A global approach for pure bending. International Journal of Engineering Research & Technology (IJERT). 2016;5(3):584-589. ISSN: 2278-0181\n'},{id:"B34",body:'\nLanteigne J. Theoretical estimation of the response of helically armored cables to tension, torsion, and bending. Journal of Applied Mechanics. 1985;52:423-432\n'},{id:"B35",body:'\nIEC 62219. Overhead electrical conductors-formed wire, concentric lay and stranded conductors. IEC. 2002;1:1-41\n'},{id:"B36",body:'\nJiang W, Wang T, Jones W. Forced vibration of coupled extensional-torsional systems. Journal of Engineering Mechanics. 1991;117:1171-1190\n'},{id:"B37",body:'\nOjo EE. Finite element formulation and analysis of the composite structure of overhead transmission lines conductors. In: Proceedings of the 10th South African Conference on Computational and Applied Mechanics. 3–5 October, 2016; South Africa, Potchefstroom: SACAM; 2016. p. 382-393\n'},{id:"B38",body:'\nOjo EE, Shindin S. Mint: Finite element analysis of the dynamic behaviour of transmission line conductors using MATLAB. Journal of Mechanics Engineering and Automation. 2014;4:142-148\n'},{id:"B39",body:'\nKwon YW, Bang H. Finite Element Method Using Matlab. 2nd ed. Boca Raton: CRC Press; 2000\n'},{id:"B40",body:'\nWilson EL, Clough RW. Dynamic response by step-by-step matrix analysis. In: Proceedings of the Symposium on the Use of Computers in Civil Engineering. 1–5 October, 1962; Portugal, Lisbon: CICE; 1962. p. 1-14\n'},{id:"B41",body:'\nNewmark MN. A method of computation for structural dynamics. Journal of Engineering Mechanics Division and ASCE Proceedings. 1959;85:EM3\n'}],footnotes:[],contributors:[{corresp:"yes",contributorFullName:"Chiemela Onunka",address:"onunka@mut.ac.za",affiliation:'
'}],corrections:null},book:{id:"6226",title:"MATLAB",subtitle:"Professional Applications in Power System",fullTitle:"MATLAB - Professional Applications in Power System",slug:"matlab-professional-applications-in-power-system",publishedDate:"September 19th 2018",bookSignature:"Ali Saghafinia",coverURL:"https://cdn.intechopen.com/books/images_new/6226.jpg",licenceType:"CC BY 3.0",editedByType:"Edited by",editors:[{id:"174893",title:"Dr.",name:"Ali",middleName:null,surname:"Saghafinia",slug:"ali-saghafinia",fullName:"Ali Saghafinia"}],productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},chapters:[{id:"62637",title:"Introductory Chapter: MATLAB Applications in Power System",slug:"introductory-chapter-matlab-applications-in-power-system",totalDownloads:882,totalCrossrefCites:0,signatures:"Ali Saghafinia",authors:[{id:"174893",title:"Dr.",name:"Ali",middleName:null,surname:"Saghafinia",fullName:"Ali 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\n
1. Introduction
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The cornea and the sclera are two conjugated quasi-spherical segments with unequal curvature radii; together they form corneoscleral (fibrous) tunic—the supporting structure of the eye capsule. Their mechanical properties play a crucial role of holding together the inner ocular structures. Despite them both being composed of connective tissue, they differ in physical (particularly, optical) and biomechanical properties [1].
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The cornea is the anterior part of the fibrous tunic of the eyeball, and it takes up 1/6 of its length. Despite it being relatively thin, its main function is protection—assured by its high durability. But the cornea also participates in light ray refraction, making up an important part of the visual apparatus; as such, it is characterized by high optical homogeneity and complete transparence.
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The cornea is an anisotropic, inhomogeneous structure; it mainly consists of highly specific connective tissue formed by parallel collagen fibrils that extend from one limb to another and act as load supporting elements [2].
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The sclera takes up the other 5/6 of the eye length and represents the posterior part of the fibrous tunic of the eyeball. Scleral tunic is the main supporting structure of the eyeball; it consists of dense collagen fibers. In contrast to cornea, the sclera has high dispersive power due to its chaotically distributed fibrils and fibers, which prevents light from entering the eye cavity from the side. In natural conditions, in the living eye, scleral elements are constantly in a strain-stress state determined by intraocular pressure and mechanical properties of the scleral tissue, as well as by anisotropy and inhomogeneity of these properties [3].
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Studying the biomechanical properties of the cornea is relevant for certain clinical needs associated with the appearance of new biomechanics examination methods, as well as the need to diagnose and monitor ectatic diseases of the cornea, to adequately select the parameters for keratorefractive surgeries, to correctly interpret the intraocular pressure (IOP) values, and, consequently, to appropriately assess IOP and monitor glaucomatous process.
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In addition, conducting studies on the biomechanical properties of the sclera is a necessary step in the research of pathogenic factors relevant for occurrence and progression of myopia, as well as finding effective means and methods of influencing the sclera in order to correct its biomechanical state.
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However, the lack of standardized terminology and uniform classification hurts the ability to compare research results and consequently hinders their introduction into the knowledge area of ophthalmology.
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\n
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2. Classification of approaches to study the biomechanics of the eye
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In accordance with different approaches, eye biomechanics can be divided into the following types:
theoretical;
physical (i.e., experimental); and
clinical.
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2.1. Theoretical biomechanics of the eye
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Theoretical biomechanics is a science that employs mathematical methodology and mathematical analysis. As applied to ophthalmology, it handles with specific physical constants characterizing elasticity, strength, and other mechanical parameters of the tissues (usually measured in vitro).
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The main theoretical approach is mathematical modeling. The research may target separate structures of the eyeball and the tunic, or the eye in its entirety. It can also include modeling of physiological or pathological processes, changes induced by specific stimuli or effects of surgical treatment.
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The results obtained from modeling can be used in experimental and clinical studies. In turn, all models are based on the figures acquired in experiments or from clinical diagnostic.
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Disadvantages of the theoretical approach in studying eye biomechanics are associated with structural complexity of the eyeball, inhomogeneity, and variability of morphology of the ocular structures, and dependence on the technological advancement of experimental and clinical research methods.
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\n
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2.2 Physical (experimental) biomechanics of the eye
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Experimental biomechanics of the eye is based on studying individual tissues and the eyeball as a whole in vitro or by conducting animal experiments using physical methods. It is the most developed subdiscipline of biomechanics with many years of research history. Capabilities of the approach are limited by post-mortem changes in eye tissues, and anatomical and physiological differences between humans and animals. The main purpose of experimental studies is to find potentially useful methods of studying biomechanical properties of eye tissues in clinical environment and to acquire data for mathematical modeling. The main advantages of experimental researches are the absence of restrictions for employed methods and approaches, and the choice of which is only limited by technological and scientific advancement.
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Methods of experimental biomechanics allow measurement of a big number of physical parameters of the cornea:
Young’s modulus (E),
Poisson’s ratio (μ),
Durability (σ),
Deformation capacity (Σ), etc.
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However, they do not fully reflect the properties of fibrous tunic of the eye in vivo.
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\n
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2.3. Clinical biomechanics of the eye
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Clinical biomechanics of the eye studies the influence of biomechanical properties of the fibrous tunic on the results of diagnostics, development, and treatment of various eye diseases. Clinical biomechanics operates on data obtained with specialized examination methods used in ophthalmology (in vivo) that characterize biomechanical properties of the fibrous tunic. Its research subject is strictly the eyeball as a whole, only allowing arbitrary delineation of the internal structures. This complicates the interpretation of data. However, in order to improve diagnostics and treatment of eye diseases, clinical methods for eye biomechanics need to have higher priority in research and development.
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The following corneal parameters can be measured clinically:
Friedenwald’s rigidity coefficient;
Corneal hysteresis;
Corneal resistance factor;
Coefficient of elasticity;
Corneal deformation.
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The biggest number of already existed studies are dedicated to investigation of biomechanical properties of the cornea, which is probably related to the specifics of corneal structure, or to its accessibility for examination.
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\n
\n
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3. Theoretical (mathematical) biomechanics
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The originator of mathematical approach to study biomechanical properties of the cornea was F.A. Rachevsky. In 1930, in his theoretical study, he pointed “…for the first time at the paramount importance of the radius of the corneal curve and especially of its thickness for specific results of intraocular pressure tonometry.” Besides that, he proved mathematically that under effect of external and internal forces, tangentially directed stress occurs in the cornea, particularly during applanation tonometry [4].
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At present, the research of corneal biomechanics is conducted in two main directions. Mathematical modeling is generally used for the calculation of parameters and prediction of results of keratorefractive surgeries [5, 6, 7, 8], as well as for the determination of possible procedural errors of applanation tonometry methods when biomechanical properties changed as the result of a surgery or a disease [9].
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The main obstacle for proper mathematical modeling is anisotropy of the cornea. The majority of the proposed models does not consider it, which limits their application in practical ophthalmology [10, 11, 12].
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According to Pinsky et al., the anisotropy of the cornea primarily depends on its structural features, that is, specific architectural organization of collagen fibers [13]. X-ray structural analysis revealed that collagen fibrils of the central area have orthogonal orientation predominantly in vertical and horizontal directions, while fibrils of the periphery have tangential orientation [14]. Pinsky et al. developed a mathematical model for corneal anisotropy mechanics that accounts for these findings [13]. Based on the finite element method, the model allows predicting biomechanical response of the cornea to tunnel cutting, radial keratotomy, and LASIK [15, 16, 17].
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In order to determine the possible error margin of applanation tonometry methods, several mathematical models have been developed [18]. Liu et al. used mathematical modeling to study isolated effects of various biometric and biomechanical parameters of the cornea on Goldmann tonometry readings [19]. Kwon et al. developed a mathematical model demonstrating the need to take into account not only corneal thickness, but also its biomechanical properties when interpreting Goldmann tonometry readings [20].
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4. Physical (experimental) biomechanics
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4.1. Normal (intact) cornea
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Experimental studies based on extensiometry revealed distinguishing biomechanical anisotropy and heterogeneity of the cornea. Corneal material acquired with a radial cut has the best durability and margin of deformation capacity. Those parameters decrease with distance from the radial direction. Corneal material stretched tangentially shows approximately the same elastic properties along the corneal disc. The samples stretched radially appeared to have the highest rigidity. In the course of the study, Poisson’s ratio was determined for various parts of the cornea. This ratio characterizes the transverse deformation lateral to stretch direction, for radial direction, it was in the range of 0.445–0.450, and for tangential direction, it was in the range from 0.290 to 0.310 (middle periphery) and from 0.340 to 0.350 (perilimbal) [21, 22].
\n
A variety of studies is dedicated to measuring the main elastic and strength properties of the cornea, but analysis of the data shows that isolated corneas exhibit big spread in the values—from 0.3 to 13.6 MPa. The phenomenon can be attributed to different experimental conditions and nonlinear nature of biomechanical properties of corneal material [23, 24, 25, 26]. Andreassen et al. studied the biomechanics of corneal discs with extensiometry; the discs were taken from patients with keratoconus after they underwent penetrating keratoplasty. The study revealed significant decrease of mechanical strength properties in pathologically altered corneas [27].
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Soergel et al. used dynamic mechanical spectroscopy to evaluate viscoelastic properties of the cornea in experimental environment. They found that elastic and shearing deformation depend on the hydration, time elapsed after death, and temperature of the tissue [28].
\n
Wang et al. calculated Young’s modulus by measuring the speed of ultrasound transmission through cadaver cornea and processing the data with Fourier analysis [29].
\n
Like ultrasound spectroscopy, Brillouin microscopy can determine intrinsic viscoelastic properties decoupled from the structural information and applied pressure. In contrast, it can measure the local acoustic properties with much higher spatial resolution and sensitivity, and the measurement is performed optically without the need for acoustic transducers or physical contact with the cornea [30].
\n
One of the techniques, holographic interferometry, is used to calculate Young’s modulus. The method is to some degree similar to videokeratography, that is, holographic technologies are used to examine the changes in corneal surface. A study conducted on an intact bull’s cornea showed Young’s modulus being two orders lower than when measured in an experiment with corneal tissue samples. The authors summarized that localization and hydration level plays the primary roles during measurement. This method, however, is limited in terms of practical use due to requiring maximum permissible laser emission in order for the resulting images to be high quality [31].
\n
\n
\n
4.2. Cornea after refractive surgery
\n
Some studies showed significant increase of tangential elasticity of the cornea after it was incised with radial cuts (up to 46.5% with an incision depth of 0.6 mm), that is, in the direction of the lesser material rigidity [32]. In certain cases, the changes led to severe complications in the long-term postoperative period. Particularly, it manifested as a significant decrease of eyeball’s resistance to trauma with potential disruption of corneal cicatrices and loss of membranes [33].
\n
Luminescent polariscopy revealed that after radial keratotomy, the main mechanical strain fell on the middle periphery of the cornea, particularly on the bottom of keratotomic incisions. An increase of intracameral pressure (analogue to intraocular pressure) raises the strain on peripheral part of the cornea and off-loads its central part, which can cause hypermetropic shift in refraction [34].
\n
However, with the appearance and widespread implementation of excimer laser technologies for correction of refraction errors, such risks have greatly decreased. It can be attributed to different mechanisms of corneal refraction change, that is, its thinning in the central area.
\n
Experimental studies on biomechanical properties of the cornea after excimer laser intervention indicate that thinning of the cornea in 6.0-mm optic zone for more than 15–20% results in significant changes of its mechanical properties. In terms of clinical relevance, the most meaningful change appears to be the significant (mean 20%) decrease of breaking load for experimental samples in comparison to the control samples. Additionally, changes in deformation properties of the cornea after laser ablation should also be taken into consideration, which manifested as lowered amount of movement the punch had to do before the cornea broke in experimental eyes in comparison to the control subjects in average by 10.72% [35].
\n
However, the mechanical properties of the data obtained using an isolated cornea cannot objectively reflect the parameters of the tissues in natural environment. Adequate information on the biomechanical state of the cornea can only be obtained from a living eye.
\n
\n
\n
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5. Clinical biomechanics
\n
\n
5.1. Normal (intact) cornea
\n
Clinical studies on the biomechanical properties of the relatively healthy cornea have been conducted since the middle of the twentieth century, but those methods remained widely unused due to various reasons.
\n
In 1937, Friedenwald suggested that rigidity coefficient could be calculated based on a logarithmic dependence between IOP changes and eye volume employing differential tonometry with Schiotz tonometer [36]. Friedenwald depicted the relation between pressure and volume in a coordinate system. As was shown by further clinical studies, the proposed coefficient strongly depends on the corneal curvature and thickness, as well as on the IOP level [37]. According to research results, the parameter suggested by Friedenwald—the rigidity coefficient—was inaccurate in eyes with deviations in biomechanics (thickness and curvature) from the norm. It was also strongly influenced by IOP.
\n
In 1936, S. F. Kalfa proposed a method of elastotonometry, that is, differential tonometry with four Maklakov tonometers weighing 5, 7.5, 10, and 15 g. Connecting the dots marked on a coordinate system forms an elastotonometric curve, which appears ascending line. The difference in mm Hg between the starting and ending points of the curve, that is, between IOP value obtained using 5.0 and 15.0 g tonometers, is called elasto-ascent. Essentially, Friedenwald’s rigidity coefficient and S. F. Kalfa’s elasto-ascent are different expressions of the same thing. In norm, the two figures are closely related, albeit not functionally [38].
\n
There are a number of techniques described by their authors as potential intravital methods for examination of biomechanical properties of the cornea, but they have not been adopted into clinical practice: electronic speckle interferometry [39], dynamic cornea visualization [40], corneal applanation and indentation [41], ultrasound elastometry [42], and photoelasticity method [43].
\n
As an alternative to holographic interferometry, a noncontact, nondisruptive method of electronic speckle interferometry was suggested; it is equally sensitive because it employs close wavelength for measurement. Advantages of the method include the absence of requirement of photographic hologram recording, which simplifies the procedure and enables real-time acquisition of corneal surface shift data using a television camera. The method is recommended for evaluation of changes in corneal biomechanics after excimer laser refractive surgery [39].
\n
Grabner et al. proposed a method of dynamic visualization of the cornea. It involves applying dosed pressure to the central area of the cornea during videokeratography by means of a special indenter and subsequent analysis of the topographic pattern. As the result, high correlation between the bending curve and depression depth was found. The form of the curve was noted to be affected by central corneal thickness, intraocular pressure, and patient age. Moreover, bending curves were different in keratoconus patients, as well as in patients who had underwent keratorefractive surgeries [40].
\n
Chang et al. studied biomechanical properties of the cornea in vivo using corneal applanation and indentation on rabbit and human eyes, regarding the cornea as a transversely isotropic material. The study showed normal Young’s modulus to vary from 1 to 5 MPa and transverse shift modulus from 10 to 30 KPa [41].
\n
Some authors used photoelasticity method to evaluate mechanical stress in the cornea involving the measurement of its polarization and optical properties [43].
\n
Scoping a large amount of clinical data, Edmund calculated Young’s modulus adhering to the hypothesis that the final form of cornea is the outcome of counteraction between tissue elasticity and intraocular pressure. The modulus values were significantly lower in keratoconus eyes when compared to norm. The study also showed significant difference between healthy and ectatic patients in relative distribution of stress in the central and peripheral areas of the cornea, which can help with the understanding of keratoconus pathogenesis. However, this method generally does not find much use in clinical practice [44].
\n
The one method most widely used in present day clinical practice involves ocular response analyzer (ORA)—a device that analyses corneal biomechanical properties based on bi-directional corneal applanation by an air pulse [45]. The method’s authors proposed to evaluate biomechanical response of the cornea by quantifying the differential inward and outward corneal response to an air pulse and thus obtaining two parameters—corneal hysteresis (CH) and corneal resistance factor (CRF). Corneal hysteresis characterizes the viscoelastic properties of the cornea responsible for the partial absorption of the air pulse energy. Corneal resistance factor is a derived parameter with high correlation to central corneal thickness that reflects the elastic properties of the cornea.
\n
Multiple studies have confirmed the usefulness of bi-directional corneal applanation for the evaluation of biomechanical properties of the cornea: they rise with the increase of the corneal thickness [46, 47]. Corneal hysteresis was in the average 10.8 ± 1.5 mm Hg and corneal resistance factor—11.0 ± 1.6 mm Hg. Statistically, a significant difference in the mean values of CH and CRF between groups of varying age was absent, with the exception of patients older than 60 years for whom the values were on lower. It is possible that the phenomenon reflects the changes in elastic properties of the cornea associated with age, but the authors also note the potential influence of other parameters (intraocular pressure and anterior-posterior axis length) that were disregarded in the study [48]. The comparison of CH and CRF in children and adults did not reveal any age-related differences [49].
\n
Studying the diurnal variations in CH and CRF parameters revealed their hourly stability, while minor changes observed between the morning and evening measurements can be explained by diurnal IOP fluctuations [50]. CH and CRF correlated strongly with corneal thickness and to a lesser degree with an amount of astigmatism. No correlation was found with keratometry, age, gender, spherical equivalent, or IOPcc [51]. Moreover, ORA shows good repeatability of biomechanical and tonometry measurements [52].
\n
Avetisov et al. studied the possibility of applying the dynamic pneumo-impression of the cornea approach to the existing corneal biomechanical properties analyzer (ORA). The fundamental principle was that at the curvature start point laying on the border of the impression area, the pneumatic jet is subject to the counter-force of IOP and corneal elasticity, in equal amounts. At the moment of maximum impression, the pneumatic jet is mainly countered by corneal elasticity—due to the maximum deformation of the cornea. As the result, a parameter named elasticity coefficient was calculated characterizing the elastic behavior of the cornea regardless of the IOP level [53].
\n
The same principle was used in CorVis device (Oculus, Germany), in which corneal deformation responding to a pulse of air is monitored with high-speed Scheimpflug camera. The device can help to measure a whole range of parameters that characterize the particularities of corneal deformation during the impression process. It records the process between the initial and the second applanations involving the cornea recovering its initial form, captures the maximum indentation point, and measures IOP [54, 55].
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\n
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5.2. Keratoconic cornea
\n
Intravital measurement of biomechanical properties of the cornea in keratoconus patients performed with dynamic bi-directional pneumo-applanation showed lower CH and CRF values than in healthy eyes. Apparent negative correlation between the CH and CRF parameters and the degree of keratoconus were also evident [56].
\n
Additionally, CH was significantly higher than CRF in the keratoconus group. The authors suggested the CH decrease of less than 8 mm Hg in conjunction with positive CH-CRF difference to be considered a stronger sign of keratoconus than isolated decrease of CH. Glaucoma patients showed reverse tendency: CRF value was higher than CH [57].
\n
Studying the parameters obtained with dynamic Scheimpflug analysis (Covis ST) showed the possibilities of the examination method for differential diagnostics of patients suspected of keratoconus or with early keratoconus from patients with normal cornea [58].
\n
\n
\n
5.3 Cornea after refractive surgery
\n
Intravital measurements of biomechanical properties of the cornea after excimer laser surgery performed using dynamic bi-directional pneumo-applanation also confirmed the loss of corneal strength. In patients who had underwent LASIK, examination showed decrease of IOP-related parameters such as corneal compensated IOP, as well as parameters reflecting the biomechanical properties. Along with that, significant correlation was observed between the amount of myopia correction and the deterioration of the biomechanical properties [59].
\n
Another study analyzed the results of dynamic bi-directional pneumo-applanation of the cornea and assessed the correlation between CH decrease and ablation depth in three patient groups: after photorefractive keratectomy, after LASIK with mechanical corneal flap creation, and after LASIK with femtosecond flap creation. The authors found that the strongest correlation was present in femto-LASIK group, while in the two other groups, it was significantly lower [60].
\n
Isolated creation of corneal flap was also found to cause minor changes in corneal refraction [61]. Roberts explained the phenomenon with a theory stating that after lamellar dissection, the corneal biomechanics change in such a way so that severed fibrils contract causing traction in the direction of limbus. With that, central corneal area deflates under the action of released fibrils inducing the so-called “hypermetropic” shift [62, 63].
\n
In parallel, a comparison of changes in biomechanical properties of the cornea after superficial and intrastromal keratectomy was done using OCULUS Corvis (Germany) tonometer. Both types of keratectomy were found to cause statistically significant decrease of biomechanical parameters [64].
\n
Despite the existing methods of measuring biomechanical properties of the cornea and the developed biomechanical models, the detection of ectasia after excimer laser vision correction varies from 0.04 to 0.6% of cases, but according to some researchers, the numbers may be an underestimation [65, 66].
\n
Iatrogenic keratectasia is known to develop due to two factors: an ectatic corneal disease that was undiagnosed in the preoperative stage and excessive thinning of the cornea [67]. In the first case, early detection of keratoconus poses objective challenges [68, 69].
\n
At the same time, even when keratoconus was timely diagnosed, the selection of candidates for keratorefractive surgeries is still difficult, and the evaluation of corneal biomechanics by means of dynamic bi-directional pneumo-applanation does not yield the necessary data.
\n
\n
\n
\n
6. Correction of corneal biomechanical properties
\n
Presently, the most common method of correcting (strengthening) biomechanical properties of the cornea is corneal cross-linking [70].
\n
The first specialists who in the 90s of the twentieth century created corneal cross-linking method for treating keratoconus were Wollensak, Spoerl, and Seiler [71]. They developed the protocol (“Dresden protocol”) for using this method of strengthening the cross-link bonds of collagen for treating progressive keratoconus involving riboflavin and ultraviolet A irradiation of the corneal stroma (UVA with a wavelength of 370 nm for peak absorption of riboflavin) [72].
\n
Careful preclinical experimental validation showed that the combination of riboflavin and UVA leads to a significant improvement of biomechanical stability of the cornea (increase of elastic modulus approximately by 300%) and the formation of large collagen molecular aggregates, including the appearance of cross links—predominantly between the fibril surface molecules and also between proteoglycans in the interfibrillar space [73, 74, 75].
\n
In the following decades, the corneal cross-linking technique has seen widespread clinical application with indications for its usage expanding significantly. Effectiveness of the method for strengthening biomechanical properties was confirmed for the treatment of not only progressive keratoconus, but also pellucid marginal degeneration and iatrogenic ectasia caused by excimer laser surgery [76].
\n
An important suggestion has been made recently for reinforcing the effect of corneal cross-linking—to combine the procedure with implantation of corneal segments [77, 78]. Comparative studies of different treatments—individually and in combination—showed the most pronounced effect to be from the combination therapy starting with the implantation of corneal segments and followed by cross-linking, and not in the reverse order. Such combination therapy also helps to achieve better results (weakening of manifest refraction and keratometric indicators) in cases with keratectasia after excimer laser surgery [79].
\n
There is another method described in the literature as directed laser ablation; it involves biomechanical approach to ablation calculations. Vaporization of the tissue thus happens on the middle periphery, which contains certain relatively flat spots, and not in the central (thin) area. The rationale is that thinning of the area leads to steepening of the cornea subsequently flattening the unablated area, which has more optical power [80]. It should be noted that in clinical practice, this method requires very careful consideration and cautiousness due to insufficient studies on its after effects.
\n
Furthermore, a multimodal approach involving implantation of intrastromal rings, CXL, and laser ablation in different configurations may provide not only stability of corneal topography, but also positive refraction result, thanks to the combination of all the methods’ advantages [81, 82, 83, 84, 85]. That said, the lack of established standards and clinical recommendations for combining different methods for the correction of corneal biomechanical properties may lead to various complications and unexpected aftermaths; it should be kept in mind when planning such treatment.
\n
\n
\n
7. Conclusion
\n
In summary, clinical relevance of studying biomechanics of the fibrous tunic is difficult to overestimate. The diversity of methods used for examination of biomechanical properties of the cornea means there is no single method that could fully satisfy the needs of practical ophthalmology. Further studies are necessary to develop simple, available, and sufficiently informative method for clinical assessment of ocular biomechanics. Moreover, the demand for techniques of correcting biomechanical properties keeps growing, and so this field of research has wide potential.
\n
\n
Conflict of interest
The author has no conflict of interest.
\n',keywords:"corneal biomechanics, refractive surgery, LASIK, keratokonus, IOP",chapterPDFUrl:"https://cdn.intechopen.com/pdfs/63146.pdf",chapterXML:"https://mts.intechopen.com/source/xml/63146.xml",downloadPdfUrl:"/chapter/pdf-download/63146",previewPdfUrl:"/chapter/pdf-preview/63146",totalDownloads:426,totalViews:169,totalCrossrefCites:0,dateSubmitted:"April 29th 2018",dateReviewed:"July 14th 2018",datePrePublished:"November 5th 2018",datePublished:"January 30th 2019",dateFinished:null,readingETA:"0",abstract:"Knowledge of biomechanical properties of eye globe is necessary both for correct selection of candidates for refractive surgery and right choice of operative intervention parameters. No less important, it is for corneal ectatic disease diagnostics and monitoring. Also it gives inestimable contribution for interpretation of intraocular pressure (IOP) indices especially in cases with irregular eye shape or after past corneal surgical procedures. Moreover, it allows studying injury mechanism by glaucoma process on optic nerve head fibers. Above it, scleral biomechanical properties research is necessary for the investigation of pathophysiologic factors of myopia manifestation and progression. This chapter is devoted to review of existed to date methods of study of eye fibrous tunic biomechanical properties. It describes mathematical, experimental, and clinical models provided evaluation of unsearchable by direct measurement parameters. It also observes effective technics of impact on both sclera and cornea with the aim of correction of its biomechanical condition.",reviewType:"peer-reviewed",bibtexUrl:"/chapter/bibtex/63146",risUrl:"/chapter/ris/63146",signatures:"Irina Bubnova",book:{id:"6843",title:"Biomechanics",subtitle:null,fullTitle:"Biomechanics",slug:"biomechanics",publishedDate:"January 30th 2019",bookSignature:"Hadi Mohammadi",coverURL:"https://cdn.intechopen.com/books/images_new/6843.jpg",licenceType:"CC BY 3.0",editedByType:"Edited by",editors:[{id:"212432",title:"Prof.",name:"Hadi",middleName:null,surname:"Mohammadi",slug:"hadi-mohammadi",fullName:"Hadi Mohammadi"}],productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"}},authors:[{id:"256707",title:"Ph.D.",name:"Irina",middleName:null,surname:"Bubnova",fullName:"Irina Bubnova",slug:"irina-bubnova",email:"bubnova.irina@gmail.com",position:null,institution:null}],sections:[{id:"sec_1",title:"1. Introduction",level:"1"},{id:"sec_2",title:"2. Classification of approaches to study the biomechanics of the eye",level:"1"},{id:"sec_2_2",title:"2.1. Theoretical biomechanics of the eye",level:"2"},{id:"sec_3_2",title:"2.2 Physical (experimental) biomechanics of the eye",level:"2"},{id:"sec_4_2",title:"2.3. Clinical biomechanics of the eye",level:"2"},{id:"sec_6",title:"3. Theoretical (mathematical) biomechanics",level:"1"},{id:"sec_7",title:"4. Physical (experimental) biomechanics",level:"1"},{id:"sec_7_2",title:"4.1. Normal (intact) cornea",level:"2"},{id:"sec_8_2",title:"4.2. Cornea after refractive surgery",level:"2"},{id:"sec_10",title:"5. Clinical biomechanics",level:"1"},{id:"sec_10_2",title:"5.1. Normal (intact) cornea",level:"2"},{id:"sec_11_2",title:"5.2. Keratoconic cornea",level:"2"},{id:"sec_12_2",title:"5.3 Cornea after refractive surgery",level:"2"},{id:"sec_14",title:"6. Correction of corneal biomechanical properties",level:"1"},{id:"sec_15",title:"7. Conclusion",level:"1"},{id:"sec_19",title:"Conflict of interest",level:"1"}],chapterReferences:[{id:"B1",body:'Iomdina EN, Bauer SM, Kotliar KE. Eye Biomechanics: Theoretical Aspects and Clinical Applications. Moscow: Real Time; 2015. p. 208\n'},{id:"B2",body:'DelMonte DW, Kim T. Anatomy and physiology of the cornea. Journal of Cataract & Refractive Surgery. 2011;37(3):588-598\n'},{id:"B3",body:'Egorova E, Borsenok S, Bessarabov A, Miligert A, Sevostyanov M, Baikin A. Biomechanical properties of sclera in groups of patients with different refraction. Ophthalmosurgery. 2015;4:65-69\n'},{id:"B4",body:'Avetisov SE, Bubnova IA, Antonov AA. Corneal biomechanics: Clinical importance, evaluation, possibilities of sistemization of examination approaches. Vestnik Oftalmologii. 2010;126(6):3-7\n'},{id:"B5",body:'Lanchares E, Calvo B, Cristóbal JA, Doblaré M. Finite element simulation of arcuates for astigmatism correction. Journal of Biomechanics. 2008;41(4):797-805. 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Interferometric technique to measure biomechanical changes in the cornea induced by refractive surgery. Journal of Cataract & Refractive Surgery. 2005;31(1):175-184\n'},{id:"B40",body:'Grabner G, Eilmsteiner R, Steindl C, Ruckhofer J, Mattioli R, Husinsky W. Dynamic corneal imaging. Journal of Cataract & Refractive Surgery. 2005;31(1):163-174\n'},{id:"B41",body:'Chang S, Hjortdal J, Maurice D, Pinsky P. Corneal Deformation by Indentation and Applanation Forces. Investigative Ophthalmology & Visual Science. Philadelphia, PA: Lippincott-Raven Publ; 1993. p. 19106\n'},{id:"B42",body:'Dupps WJ, Netto MV, Herekar S. Surface wave elastometry of the cornea in porcine and human donor eyes. Journal of Refractive Surgery. 2007;23(1):66-75\n'},{id:"B43",body:'Volokov V, Juravlev A, Malyshev L, Saulgosis U, Nekrasov U, Pavilainen V. Current state and prospects of application of the method of photoelasticity in ophthalmology. Journal of Ophthalmology. 1990;8:479-482\n'},{id:"B44",body:'Edmund C. Corneal topography and elasticity in normal and keratoconic eyes. A methodological study concerning the pathogenesis of keratoconus. Acta Ophthalmologica. Supplement. 1989;193:1-36\n'},{id:"B45",body:'Luce DA. Determining in vivo biomechanical properties of the cornea with an ocular response analyzer. Journal of Cataract & Refractive Surgery. 2005;31(1):156-162. DOI: 10.1016/j.jcrs.2004.10.044\n'},{id:"B46",body:'Medeiros FA, Weinreb RN. Evaluation of the influence of corneal biomechanical properties on intraocular pressure measurements using the ocular response analyzer. Journal of Glaucoma. 2006;15(5):364-370\n'},{id:"B47",body:'Annette H, Kristina L, Bernd S, Mark-Oliver F, Wolfgang W. Effect of central corneal thickness and corneal hysteresis on tonometry as measured by dynamic contour tonometry, ocular response analyzer, and Goldmann tonometry in glaucomatous eyes. Journal of Glaucoma. 2008;17(5):361-365\n'},{id:"B48",body:'Kotecha A, Elsheikh A, Roberts CR, Zhu H, Garway-Heath DF. Corneal thickness-and age-related biomechanical properties of the cornea measured with the ocular response analyzer. Investigative Ophthalmology & Visual Science. 2006;47(12):5337-5347\n'},{id:"B49",body:'Kirwan C, O’keefe M, Lanigan B. Corneal hysteresis and intraocular pressure measurement in children using the reichert ocular response analyzer. American Journal of Ophthalmology. 2006;142(6):990-992\n'},{id:"B50",body:'Gonzalez-Meijome JM, QueirOS A, Jorge J, DIAz-Rey A, Parafita MA. Intraoffice variability of corneal biomechanical parameters and intraocular pressure (IOP). Optometry and Vision Science. 2008;85(6):457-462\n'},{id:"B51",body:'Montard R, Kopito R, Touzeau O, Allouch C, Letaief I, Borderie V, et al. Ocular response analyzer: Feasibility study and correlation with normal eyes. Journal Français d\'Ophtalmologie. 2007;30(10):978-984\n'},{id:"B52",body:'Moreno-Montanés J, Maldonado MJ, García N, Mendiluce L, García-Gómez PJ, Seguí-Gómez M. Reproducibility and clinical relevance of the ocular response analyzer in nonoperated eyes: Corneal biomechanical and tonometric implications. Investigative Ophthalmology & Visual Science. 2008;49(3):968-974\n'},{id:"B53",body:'Avetisov SE, Novikov IA, Bubnova IA, Antonov AA, Siplivyi VI. Determination of corneal elasticity coefficient using the ORA database. Journal of Refractive Surgery. 2010;26(7):520-524\n'},{id:"B54",body:'Reznicek L, Muth D, Kampik A, Neubauer AS, Hirneiss C. Evaluation of a novel Scheimpflug-based non-contact tonometer in healthy subjects and patients with ocular hypertension and glaucoma. British Journal of Ophthalmology. 2013;97(11):1410-1414\n'},{id:"B55",body:'Asaoka R, Nakakura S, Tabuchi H, Murata H, Nakao Y, Ihara N, et al. The relationship between Corvis ST tonometry measured corneal parameters and intraocular pressure, corneal thickness and corneal curvature. PLoS One. 2015;10(10):e0140385\n'},{id:"B56",body:'Fontes BM, Ambrósio R, Velarde GC, Nosé W. Ocular response analyzer measurements in keratoconus with normal central corneal thickness compared with matched normal control eyes. Journal of Refractive Surgery. 2011;27(3):209-215\n'},{id:"B57",body:'Touboul D, Roberts C, Kérautret J, Garra C, Maurice-Tison S, Saubusse E, et al. Correlations between corneal hysteresis, intraocular pressure, and corneal central pachymetry. Journal of Cataract & Refractive Surgery. 2008;34(4):616-622\n'},{id:"B58",body:'Francis M, Pahuja N, Shroff R, Gowda R, Matalia H, Shetty R, et al. Waveform analysis of deformation amplitude and deflection amplitude in normal, suspect, and keratoconic eyes. Journal of Cataract & Refractive Surgery. 2017;43(10):1271-1280\n'},{id:"B59",body:'Pedersen IB, Bak-Nielsen S, Vestergaard AH, Ivarsen A, Hjortdal J. Corneal biomechanical properties after LASIK, ReLEx flex, and ReLEx smile by Scheimpflug-based dynamic tonometry. Graefe\'s Archive for Clinical and Experimental Ophthalmology. 2014;252(8):1329-1335\n'},{id:"B60",body:'Hamilton DR, Johnson RD, Lee N, Bourla N. Differences in the corneal biomechanical effects of surface ablation compared with laser in situ keratomileusis using a microkeratome or femtosecond laser. Journal of Cataract & Refractive Surgery. 2008;34(12):2049-2056\n'},{id:"B61",body:'Güell JL, Velasco F, Roberts C, Sisquella MT, Mahmoud A. Corneal flap thickness and topography changes induced by flap creation during laser in situ keratomileusis. Journal of Cataract & Refractive Surgery. 2005;31(1):115-119. DOI: 10.1016/j.jcrs.2004.09.045\n'},{id:"B62",body:'Potgieter FJ, Roberts C, Cox IG, Mahmoud AM, Herderick EE, Roetz M, et al. Prediction of flap response. Journal of Cataract & Refractive Surgery. 2005;31(1):106-114\n'},{id:"B63",body:'Roberts C. Biomechanical customization: The next generation of laser refractive surgery. Journal of Cataract & Refractive Surgery. 2005;31(1):2-5\n'},{id:"B64",body:'Hassan Z, Modis L, Szalai E, Berta A, Nemeth G. Examination of ocular biomechanics with a new Scheimpflug technology after corneal refractive surgery. Contact Lens & Anterior Eye. 2014;37(5):337-341. DOI: 10.1016/j.clae.2014.05.001\n'},{id:"B65",body:'Vahdati A, Seven I, Mysore N, Randleman JB, Dupps WJ. Computational biomechanical analysis of asymmetric ectasia risk in unilateral post-LASIK ectasia. Journal of Refractive Surgery. 2016;32(12) :811-820. DOI: 10.3928/1081597X-20160929-01\n'},{id:"B66",body:'Santhiago MR, Giacomin NT, Smadja D, Bechara SJ. Ectasia risk factors in refractive surgery. Clinical Ophthalmology (Auckland, NZ). 2016;10:713. DOI: 10.2147/OPTH.S51313\n'},{id:"B67",body:'Pallikaris IG, Kymionis GD, Astyrakakis NI. Corneal ectasia induced by laser in situ keratomileusis. Journal of Cataract & Refractive Surgery. 2001;27(11):1796-1802\n'},{id:"B68",body:'Comaish IF, Lawless MA. Progressive post-LASIK keratectasia: Biomechanical instability or chronic disease process? Journal of Cataract & Refractive Surgery. 2002;28(12):2206-2213\n'},{id:"B69",body:'Dupps WJ. Biomechanical modeling of corneal ectasia. Journal of Refractive Surgery. 2007;23(1):186-190\n'},{id:"B70",body:'Roberts CJ, Dupps WJ. Biomechanics of corneal ectasia and biomechanical treatments. Journal of Cataract & Refractive Surgery. 2014;40(6):991-998. DOI: 10.1016/j.jcrs.2014.04.013\n'},{id:"B71",body:'Spoerl E, Seiler T. Techniques for stiffening the cornea. Journal of Refractive Surgery. 1999;15(6):711-713\n'},{id:"B72",body:'Spoerl E, Mrochen M, Sliney D, Trokel S, Seiler T. Safety of UVA-riboflavin cross-linking of the cornea. Cornea. 2007;26(4):385-389\n'},{id:"B73",body:'Wollensak G, Spoerl E, Seiler T. Stress-strain measurements of human and porcine corneas after riboflavin–ultraviolet-A-induced cross-linking. Journal of Cataract & Refractive Surgery. 2003;29(9):1780-1785\n'},{id:"B74",body:'Kohlhaas M, Spoerl E, Schilde T, Unger G, Wittig C, Pillunat LE. Biomechanical evidence of the distribution of cross-links in corneastreated with riboflavin and ultraviolet A light. Journal of Cataract & Refractive Surgery. 2006;32(2):279-283\n'},{id:"B75",body:'Seiler T, Hafezi F. Corneal cross-linking-induced stromal demarcation line. Cornea. 2006;25(9):1057-1059\n'},{id:"B76",body:'Hersh PS, Greenstein SA, Fry KL. Corneal collagen crosslinking for keratoconus and corneal ectasia: One-year results. Journal of Cataract & Refractive Surgery. 2011;37(1):149-160. DOI: 10.1016/j.jcrs.2010.07.030\n'},{id:"B77",body:'Dauwe C, Touboul D, Roberts CJ, Mahmoud AM, Kérautret J, Fournier P, et al. Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus. Journal of Cataract & Refractive Surgery. 2009;35(10):1761-1767. DOI: 10.1016/j.jcrs.2009.05.033\n'},{id:"B78",body:'Kılıç A, Kamburoglu G, Akıncı A.Riboflavin injection into the corneal channel for combined collagen crosslinking and intrastromal corneal ring segment implantation. Journal of Cataract & Refractive Surgery. 2012;38(5):878-883\n'},{id:"B79",body:'Coskunseven E, Jankov MR II, Hafezi F, Atun S, Arslan E, Kymionis GD. Effect of treatment sequence in combined intrastromal corneal rings and corneal collagen crosslinking for keratoconus. Journal of Cataract & Refractive Surgery. 2009;35(12):2084-2091\n'},{id:"B80",body:'Cennamo G, Intravaja A, Boccuzzi D, Marotta G, Cennamo G. Treatment of keratoconus by topography-guided customized photorefractive keratectomy: Two-year follow-up study. Journal of Refractive Surgery. 2008;24(2):145-149\n'},{id:"B81",body:'Stojanovic A, Zhang J, Chen X, Nitter TA, Chen S, Wang Q. Topography-guided transepithelial surface ablation followed by corneal collagen cross-linking performed in a single combined procedure. Journal of Refractive Surgery. 2010;26(2):145-152. DOI: 10.3928/1081597X-20100121-10\n'},{id:"B82",body:'Krueger RR, Kanellopoulos AJ. Stability of simultaneous topography-guided photorefractive keratectomy and riboflavin/UVA cross-linking for progressive keratoconus. Journal of Refractive Surgery. 2010;26(10):S827-SS32. DOI: 10.3928/1081597X-20100921-11\n'},{id:"B83",body:'Kamburoglu G, Ertan A. Intacs implantation with sequential collagen cross-linking treatment in postoperative LASIK ectasia. Journal of Refractive Surgery. 2008;24(7):S726-S7S9\n'},{id:"B84",body:'Kanellopoulos AJ. Comparison of sequential vs same-day simultaneous collagen cross-linking and topography-guided PRK for treatment of keratoconus. Journal of Refractive Surgery. 2009;25(9):S812-S8S8. DOI: 10.3928/1081597X-20090813-10\n'},{id:"B85",body:'Kymionis GD, Kontadakis GA, Kounis GA, Portaliou DM, Karavitaki AE, Magarakis M, et al. Simultaneous topography-guided PRK followed by corneal collagen cross-linking for keratoconus. Journal of Refractive Surgery. 2009;25(9):S807-SS11. DOI: 10.3928/1081597X-20090813-09\n'}],footnotes:[],contributors:[{corresp:"yes",contributorFullName:"Irina Bubnova",address:"bubnova.irina@gmail.com",affiliation:'
Research Institute of Eye Diseases, Moscow, Russian Federation
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The company was founded in Vienna in 2004 by Alex Lazinica and Vedran Kordic, two PhD students researching robotics. While completing our PhDs, we found it difficult to access the research we needed. So, we decided to create a new Open Access publisher. A better one, where researchers like us could find the information they needed easily. The result is IntechOpen, an Open Access publisher that puts the academic needs of the researchers before the business interests of publishers.
",metaTitle:"Our story",metaDescription:"The company was founded in Vienna in 2004 by Alex Lazinica and Vedran Kordic, two PhD students researching robotics. While completing our PhDs, we found it difficult to access the research we needed. So, we decided to create a new Open Access publisher. A better one, where researchers like us could find the information they needed easily. The result is IntechOpen, an Open Access publisher that puts the academic needs of the researchers before the business interests of publishers.",metaKeywords:null,canonicalURL:"/page/our-story",contentRaw:'[{"type":"htmlEditorComponent","content":"
We started by publishing journals and books from the fields of science we were most familiar with - AI, robotics, manufacturing and operations research. Through our growing network of institutions and authors, we soon expanded into related fields like environmental engineering, nanotechnology, computer science, renewable energy and electrical engineering, Today, we are the world’s largest Open Access publisher of scientific research, with over 4,200 books and 54,000 scientific works including peer-reviewed content from more than 116,000 scientists spanning 161 countries. Our authors range from globally-renowned Nobel Prize winners to up-and-coming researchers at the cutting edge of scientific discovery.
\\n\\n
In the same year that IntechOpen was founded, we launched what was at the time the first ever Open Access, peer-reviewed journal in its field: the International Journal of Advanced Robotic Systems (IJARS).
\\n\\n
The IntechOpen timeline
\\n\\n
2004
\\n\\n
\\n\\t
Intech Open is founded in Vienna, Austria, by Alex Lazinica and Vedran Kordic, two PhD students, and their first Open Access journals and books are published.
\\n\\t
Alex and Vedran launch the first Open Access, peer-reviewed robotics journal and IntechOpen’s flagship publication, the International Journal of Advanced Robotic Systems (IJARS).
\\n
\\n\\n
2005
\\n\\n
\\n\\t
IntechOpen publishes its first Open Access book: Cutting Edge Robotics.
\\n
\\n\\n
2006
\\n\\n
\\n\\t
IntechOpen publishes a special issue of IJARS, featuring contributions from NASA scientists regarding the Mars Exploration Rover missions.
\\n
\\n\\n
2008
\\n\\n
\\n\\t
Downloads milestone: 200,000 downloads reached
\\n
\\n\\n
2009
\\n\\n
\\n\\t
Publishing milestone: the first 100 Open Access STM books are published
\\n
\\n\\n
2010
\\n\\n
\\n\\t
Downloads milestone: one million downloads reached
\\n\\t
IntechOpen expands its book publishing into a new field: medicine.
\\n
\\n\\n
2011
\\n\\n
\\n\\t
Publishing milestone: More than five million downloads reached
\\n\\t
IntechOpen publishes 1996 Nobel Prize in Chemistry winner Harold W. Kroto’s “Strategies to Successfully Cross-Link Carbon Nanotubes”. Find it here.
\\n\\t
IntechOpen and TBI collaborate on a project to explore the changing needs of researchers and the evolving ways that they discover, publish and exchange information. The result is the survey “Author Attitudes Towards Open Access Publishing: A Market Research Program”.
\\n\\t
IntechOpen hosts SHOW - Share Open Access Worldwide; a series of lectures, debates, round-tables and events to bring people together in discussion of open source principles, intellectual property, content licensing innovations, remixed and shared culture and free knowledge.
\\n
\\n\\n
2012
\\n\\n
\\n\\t
Publishing milestone: 10 million downloads reached
\\n\\t
IntechOpen holds Interact2012, a free series of workshops held by figureheads of the scientific community including Professor Hiroshi Ishiguro, director of the Intelligent Robotics Laboratory, who took the audience through some of the most impressive human-robot interactions observed in his lab.
\\n
\\n\\n
2013
\\n\\n
\\n\\t
IntechOpen joins the Committee on Publication Ethics (COPE) as part of a commitment to guaranteeing the highest standards of publishing.
\\n
\\n\\n
2014
\\n\\n
\\n\\t
IntechOpen turns 10, with more than 30 million downloads to date.
\\n\\t
IntechOpen appoints its first Regional Representatives - members of the team situated around the world dedicated to increasing the visibility of our authors’ published work within their local scientific communities.
\\n
\\n\\n
2015
\\n\\n
\\n\\t
Downloads milestone: More than 70 million downloads reached, more than doubling since the previous year.
\\n\\t
Publishing milestone: IntechOpen publishes its 2,500th book and 40,000th Open Access chapter, reaching 20,000 citations in Thomson Reuters ISI Web of Science.
\\n\\t
40 IntechOpen authors are included in the top one per cent of the world’s most-cited researchers.
\\n\\t
Thomson Reuters’ ISI Web of Science Book Citation Index begins indexing IntechOpen’s books in its database.
\\n
\\n\\n
2016
\\n\\n
\\n\\t
IntechOpen is identified as a world leader in Simba Information’s Open Access Book Publishing 2016-2020 report and forecast. IntechOpen came in as the world’s largest Open Access book publisher by title count.
\\n
\\n\\n
2017
\\n\\n
\\n\\t
Downloads milestone: IntechOpen reaches more than 100 million downloads
\\n\\t
Publishing milestone: IntechOpen publishes its 3,000th Open Access book, making it the largest Open Access book collection in the world
We started by publishing journals and books from the fields of science we were most familiar with - AI, robotics, manufacturing and operations research. Through our growing network of institutions and authors, we soon expanded into related fields like environmental engineering, nanotechnology, computer science, renewable energy and electrical engineering, Today, we are the world’s largest Open Access publisher of scientific research, with over 4,200 books and 54,000 scientific works including peer-reviewed content from more than 116,000 scientists spanning 161 countries. Our authors range from globally-renowned Nobel Prize winners to up-and-coming researchers at the cutting edge of scientific discovery.
\n\n
In the same year that IntechOpen was founded, we launched what was at the time the first ever Open Access, peer-reviewed journal in its field: the International Journal of Advanced Robotic Systems (IJARS).
\n\n
The IntechOpen timeline
\n\n
2004
\n\n
\n\t
Intech Open is founded in Vienna, Austria, by Alex Lazinica and Vedran Kordic, two PhD students, and their first Open Access journals and books are published.
\n\t
Alex and Vedran launch the first Open Access, peer-reviewed robotics journal and IntechOpen’s flagship publication, the International Journal of Advanced Robotic Systems (IJARS).
\n
\n\n
2005
\n\n
\n\t
IntechOpen publishes its first Open Access book: Cutting Edge Robotics.
\n
\n\n
2006
\n\n
\n\t
IntechOpen publishes a special issue of IJARS, featuring contributions from NASA scientists regarding the Mars Exploration Rover missions.
\n
\n\n
2008
\n\n
\n\t
Downloads milestone: 200,000 downloads reached
\n
\n\n
2009
\n\n
\n\t
Publishing milestone: the first 100 Open Access STM books are published
\n
\n\n
2010
\n\n
\n\t
Downloads milestone: one million downloads reached
\n\t
IntechOpen expands its book publishing into a new field: medicine.
\n
\n\n
2011
\n\n
\n\t
Publishing milestone: More than five million downloads reached
\n\t
IntechOpen publishes 1996 Nobel Prize in Chemistry winner Harold W. Kroto’s “Strategies to Successfully Cross-Link Carbon Nanotubes”. Find it here.
\n\t
IntechOpen and TBI collaborate on a project to explore the changing needs of researchers and the evolving ways that they discover, publish and exchange information. The result is the survey “Author Attitudes Towards Open Access Publishing: A Market Research Program”.
\n\t
IntechOpen hosts SHOW - Share Open Access Worldwide; a series of lectures, debates, round-tables and events to bring people together in discussion of open source principles, intellectual property, content licensing innovations, remixed and shared culture and free knowledge.
\n
\n\n
2012
\n\n
\n\t
Publishing milestone: 10 million downloads reached
\n\t
IntechOpen holds Interact2012, a free series of workshops held by figureheads of the scientific community including Professor Hiroshi Ishiguro, director of the Intelligent Robotics Laboratory, who took the audience through some of the most impressive human-robot interactions observed in his lab.
\n
\n\n
2013
\n\n
\n\t
IntechOpen joins the Committee on Publication Ethics (COPE) as part of a commitment to guaranteeing the highest standards of publishing.
\n
\n\n
2014
\n\n
\n\t
IntechOpen turns 10, with more than 30 million downloads to date.
\n\t
IntechOpen appoints its first Regional Representatives - members of the team situated around the world dedicated to increasing the visibility of our authors’ published work within their local scientific communities.
\n
\n\n
2015
\n\n
\n\t
Downloads milestone: More than 70 million downloads reached, more than doubling since the previous year.
\n\t
Publishing milestone: IntechOpen publishes its 2,500th book and 40,000th Open Access chapter, reaching 20,000 citations in Thomson Reuters ISI Web of Science.
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40 IntechOpen authors are included in the top one per cent of the world’s most-cited researchers.
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Thomson Reuters’ ISI Web of Science Book Citation Index begins indexing IntechOpen’s books in its database.
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2016
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IntechOpen is identified as a world leader in Simba Information’s Open Access Book Publishing 2016-2020 report and forecast. IntechOpen came in as the world’s largest Open Access book publisher by title count.
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2017
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Downloads milestone: IntechOpen reaches more than 100 million downloads
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Publishing milestone: IntechOpen publishes its 3,000th Open Access book, making it the largest Open Access book collection in the world
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