Finite Element Models of the Human Lens PDF Download
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Author: Sally Hiu Ching Che
Publisher:
ISBN:
Category : Cataract
Languages : en
Pages : 134
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Book Description
Author: Sally Hiu Ching Che
Publisher:
ISBN:
Category : Cataract
Languages : en
Pages : 134
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Book Description
Author: Tri Le
Publisher:
ISBN: 9780542226847
Category : Engineering, Civil
Languages : en
Pages :
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Book Description
The crystalline human lens is modeled by using the finite element software, ABAQUS/CAE Version 6.5-1 as an axisymmetric shell to study the optical power and displacement of anterior and posterior poles induced due to zonule traction. Several different element types were tested to obtain the optimum mesh. These elements were three and six-noded triangular hybrid and four-noded quadrilateral hybrid for modeling of the cortex and nucleus. Constant strain triangular and regular quadrilateral elements were examined for modeling the capsule. One dimensional two degree of freedom spring elements were used to model the anterior, posterior, and equatorial zonules. Six different lens profiles were selected to mathematically model the lens geometry, which included Lizak; Krueger A; Krueger B; Strenk A; Strenk B; and Trial lens. A displacement-based incremental loading history was applied to the equatorial zonule to conduct geometric nonlinear analysis. The converged solution was obtained by coupling Hilbert L-2 norm and equating external work done to internal system strain energy. The converged and optimum solution was compared with analytical solution reported in literature and was selected to conduct a comprehensive parametric study. (Abstract shortened by UMI.).
Author: Venetia V. Chan
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
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Book Description
A three-dimensional finite element model was created to analyze the mechanical interactions between the various substructures within the human eye. During certain activities, mechanical interactions may lead to a resultant distribution of stresses within the eye that may in turn produce various retinal diseases. The entire eye was modeled using dynamic finite element analysis to incorporate the mechanical effects of all of the substructures on the retina. A set of mechanical properties for each substructure was determined from previously published studies. Saccadic motion was modeled in the normal human eye to determine the location and magnitude of peak stresses in the retina and optic nerve head during initial loading. After 0.6125 ms, stresses as high as 5.4 x 107 Pa were reached. The peak stresses occurred in the portions of the retina and the optic nerve head close to the boundary between these two substructures.
Author: Kehao Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Author: Cynthia J. Roberts
Publisher: Kugler Publications
ISBN: 9062998860
Category : Medical
Languages : en
Pages : 546
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Book Description
Covering all major components of the ocular system, this state-of-the-art text is essential for vision scientists, biomedical engineers, and advanced clinicians with an interest in the role of mechanics in ocular function, disease, therapeutics, and surgery. With every chapter, leading experts strengthen the arguments that biomechanics is an indispensable and rapidly evolving tool for understanding and managing ocular disease.
Author: Rajendra Acharya U
Publisher: Artech House
ISBN: 1596932090
Category : Computers
Languages : en
Pages : 378
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Book Description
This groundbreaking resource gives you full details on state-of-the-art 2D and 3D eye imaging and modeling techniques that are paving the way to breakthrough clinical applications in eye health. ItOCOs the first book to explore in depth a new generation of computational methods that combine image processing, simulation, and statistical discrimination tools in efforts to improve early detection of cataracts, diabetic retinopathy, glaucoma, iridocyclitis, corneal haze, maculopathy, and other visual impairments and conditions."
Author: Luka Sterle
Publisher:
ISBN:
Category :
Languages : en
Pages : 85
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Book Description
Biomechanical properties of ocular tissues are assumed to play an important role in the pathogenesis of a variety of ocular diseases. This is particularly true for glaucoma, where the tissue biomechanics appears to determine which level of intraocular pressure can be tolerated in an individual eye. In the recent years several mathematical models were established and measurements of ocular biomechanical properties were obtained from in vitro and in vivo measurements. In this master thesis we developed finite element modeling of the human eye. New algorithms integrated all available data on ocular biomechanical properties, available at the Center of Medical Physics and Biomedical Engineering from interferometric measurements.
Author: E. Y. K. Ng
Publisher: CRC Press
ISBN: 1439869936
Category : Technology & Engineering
Languages : en
Pages : 432
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Book Description
Advanced image processing and mathematical modeling techniques are increasingly being used for the early diagnosis of eye diseases. A comprehensive review of the field, Human Eye Imaging and Modeling details the latest advances and analytical techniques in ocular imaging and modeling. The first part of the book looks at imaging of the fundus as well as infrared imaging. It begins by exploring developments in the analysis of fundus images, particularly for the diagnosis of diabetic retinopathy and glaucoma. It also reviews anterior segment imaging and reports on developments in ocular thermography, especially the use of thermal imaging as the basis of tear evaporimetry and dry eye diagnosis. The second part of the book delves into mathematical modeling of the human eye. Coverage includes modeling of the eye during retinal laser surgery, a framework for optical simulation, heat distribution using a 3D web-splines solution, and exposure to laser radiation. The text also examines computer simulation of the human eye based on principles of heat transfer, as well as various bioheat equations to predict interior temperatures based on the surface temperature. Featuring contributions by established experts in eye imaging, this is a valuable reference for medical personnel and researchers who want to know more about state-of-the-art computer-based imaging and detection methods. It presents novel imaging and modeling algorithms that can aid in early diagnosis, with the aim of enriching the lives of people suffering from eye abnormalities.
Author: Geoffrey S. Wilde
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Computational models of human accommodation hold the promise of an improved under- standing of the mechanism and of the development of presbyopia. A detailed and reliable model could greatly assist the design of treatments to restore accommodation to presbyopic eyes. However, a large quantity of data is required for such an endeavour. Currently, the details of the age-related increase in the stiffness of the lens is a major source of uncertainty as the published data differ markedly depending on the form of testing employed. A new version of the spinning lens test is presented, based on the method originated by Fisher, R. F. (1971) 'The elastic constants of the human lens', Journal of Physiology, 212(1):147-180. This test assesses the stiffness of the lens substance by photographically measuring the deformations induced by rotation of the lens about its axis of symmetry. The principal changes introduced in the present version are the removal of the capsule from the lens prior to testing, the synchronization of the photography with the orientation of the lens, and the use of a hyperelastic finite-element model of the test coupled with a numerical op- timization procedure to quantify the heterogeneous stiffness of the lens. These alterations, together with further improvements, provide a substantially more accurate means of measur- ing the stiffness of the lens 'substance'. Measurements made with the new test on a series of human lenses are reported. Good- quality tests were obtained for 29 lenses aged from 12 to 58 years. The older lenses were found to be much stiffer than younger lenses. In younger lenses the cortex of the lens is found to be stiffer than the nucleus, but the nucleus stiffens more rapidly, surpassing the cortex by about 44 years. These results differ substantially from those of the original spinning test. The stiffness values calculated for the lens substance are used in a series of hyperelastic finite-element models of the accommodation mechanism. Models corresponding to subjects aged 29 and 45 years follow clinical measurements of the decline in accommodation am- plitude between these ages. Adjusting the material parameters values indicates that it is the increase in stiffness which is largely responsible for the modelled fall in accommodation am- plitude. The 45-year model is adapted to represent the effect of laser lentotomy, a proposed presbyopia treatment. Among the lentotomy options trialled, the best result is a modest O.4D increase in the modelled accommodation amplitude.
Author: Begoña Calvo Lopez
Publisher: Springer Science & Business Media
ISBN: 9400745524
Category : Technology & Engineering
Languages : en
Pages : 196
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Book Description
This book addresses patient-specific modeling. It integrates computational modeling, experimental procedures, imagine clinical segmentation and mesh generation with the finite element method (FEM) to solve problems in computational biomedicine and bioengineering. Specific areas of interest include cardiovascular problems, ocular and muscular systems and soft tissue modeling. Patient-specific modeling has been the subject of serious research over the last seven years and interest in the area is continually growing and this area is expected to further develop in the near future.
