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Wyszukujesz frazę "tonometry" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
Applanation pressure function in Goldmann tonometry and its correction
Autorzy:
Śródka, W.
Powiązania:
https://bibliotekanauki.pl/articles/306833.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
eyeball
biomechanical model
tonometry
IOP
correction factors
gałka oczna
tonometria
korekcja
model biomechaniczny
Opis:
So far applanation tonometry has not worked out any theoretical basis for correcting the result of intraocular pressure measurement carried out on a cornea with noncalibration dimensions by means of the Goldmann tonometer. All the tables of instrument reading corrections for cornea thickness or cornea curvature radius are based exclusively on measurements. This paper represents an attempt at creating a mechanical description of corneal apex deformation in Goldmann applanation tonometry. The functional dependence between intraocular pressure and the pressure exerted on the corneal apex by the tonometer was determined from a biomechanical model. Numerical GAT simulations, in which this function was also interrelated with the cornea’s curvature radius and thickness were run and a constitutive equation for applanation tonometry, i.e. a full analytical description of intraocular pressure as a function of the above variables, was derived on this basis. The correction factors were defined and an algorithm for correcting the measured pressure was formulated. The presented formalism puts the results of experimental tonometry in new light. Analytical correction factors need not to come exclusively from measurements. A geometric interdependence between them and their dependence on pressure have been revealed. The theoretical description of applanation tonometry contained in the constitutive equation consists of a pressure function developed for a cornea with calibration dimensions and a coefficient correcting this calibration function, dependent exclusively on the cornea’s actual thickness and curvature radius. The calibration function is a generalization of the Imbert–Fick law.
Źródło:
Acta of Bioengineering and Biomechanics; 2013, 15, 3; 97-106
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of corneal and fatty tissues biomechanical response in dynamic tonometry tests by using inverse models
Autorzy:
Jannesari, M.
Kadkhodaei, M.
Mosaddegh, P.
Kasprzak, H.
Behrouz, M. J.
Powiązania:
https://bibliotekanauki.pl/articles/307551.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
biomechanika rogówki
okulistyka
tkanka tłuszczowa
tonometria
corneal biomechanics
fatty tissue
dynamic tonometry
inverse finite element method
Opis:
The assessment of corneal biomechanics is essential for studying ophthalmological operations, such as refractive surgeries, and for more accurate estimation of intraocular pressure. The chief aim of the current study is to characterize corneal and fatty tissues in order to construct a model to predict eye globe behavior during dynamic tonometry tests. Methods: In the present study, images from corneal deformation, acquired from Corvis ST tonometer, were processed. Then, corneal pure displacement and eye globe retraction were calculated. Utilizing inverse finite element method, corneal material properties were calculated in order to predict pure deformation obtained from Corvis ST. Using a similar approach, material parameters of fatty tissue were estimated in order to predict the eye globe retraction. The model used for fatty tissue was considered as corneal boundary condition in a forward finite element model to create a joint model, which could simulate corneal behavior in dynamic tonometry tests. Results: It was shown that an isotropic material model is accurate enough to predict corneal deformation in dynamic tonometry tests. Moreover, effects of IOP on the estimated material properties were investigated. Finally, utilizing the joint model, it was demonstrated that there is strong correlation between corneal stiffness and the biomechanical parameter introduced by Corvis ST. Conclusions: An eye globe model was constructed and characterized by two distinct inverse models for corneal and fatty tissue. This model can be utilized for predicting eye globe behavior during dynamic tonometry tests besides other ophthalmological operations.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 1; 39-48
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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