Wyniki wyszukiwania - Biblioteka Nauki

1

Distribution of parameters of elliptic approximation of the human pupil

100%

Szmigiel M. A. , Kasprzak H.

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2015

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tom Vol. 45, nr 1

41--50

EN

The paper describes the results of measurements of the shape of the human eye pupil with the use of a high-speed CCD camera. Sequences of 2000 frames were recorded within 10 s. The examination was performed on a group of patients. For each patient, the age and intraocular pressure were identified. The form of the pupil was approximated by an ellipse and parameters of area, eccentricity, lengths of semi axes and orientation angle were calculated. Correlations between pairs of averaged parameters for all measurements were analyzed. Distribution of averaged geometrical parameters of the pupil was examined for all measured pupils. Significant correlation was found between the age and the pupil area S. The average eccentricity ε of the pupil was 0.285 ± 0.083. There were no statistical differences between pupil eccentricities of both eyes. The average value of orientation angle α of the longer semi-axis a of the ellipse to horizon was 83.3°. Also the difference of orientation angle α for the left eye (85.2°) and the right eye (93.2°) was statistically insignificant.

2

New shape of a videokeratometric illuminator

100%

Siedlecki D. , Kasprzak H.

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tom Vol. 32, nr 4

665-672

EN

The aim of this paper is to define such shape of a videokeratometric Placido disc-based illuminator that would guarantee flat image formation and, consequently, sharp and reliable information an corneal geometry. It is especially important for contact lens fitting to have reliable corneal data in a corneal peripheral area. It has been proved that shape of this stimulator profile depends on assumed corneal geometry. The ellipsoidal corneal shape has been assumed. The results show that the surface on which Placido rings are painted should have a cigar-like shape. Probably none of the devices used currently in clinical practice have such shape.

3

Kronika

80%

Ławniczak-Jabłońska K. , Nowina-Konopka M. , Sobiczewski A. , Kasprzak H.

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2004

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tom T. 55, z. 5

236-239

PL

Tytuły profesorskie. Polska członkiem ESRF. Pamięci Władysława Natansona. Kryształowa Brukselka w Bronowicach. Nazwa pierwiastka 111. Naruszenie parzystości w rozpraszaniu elektron-elektron. Zerowa rozszerzalność cieplna. Trójkąt bermudzki dla satelitów? Konferencja optyki stosowanej.

4

Application of coherence function for calculating time shifts between axial corneal displacements and electrical heart activity

80%

Danielewska M. , Kowalska M. , Kasprzak H.

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tom Vol. 31, no. 1

17-25

EN

The heart activity is one of the most important factors influencing the ocular pulsation. It is known that the high correlation between axial corneal displacements and cardiovascular system activity exists. However, phase relationships between those factors are still unknown. The main goal of the research was to measure noninvasively longitudinal corneal apex displacement (LCAD) of the left eye, applying an ultrasonic sensor. Synchronically, the electrical heart activity (ECG) was recorded in Einthoven's triangle. To find phase dependencies between these signals the coherence function was used. It is observed that coherence value, computed between the first five harmonics of both signals, is different for shifted signals along each other. Therefore, the time delay between the ECG and LCAD signals, for which particular harmonic achieves the maximum of coherence function, was examined. It can be noticed that for increasing number of the signals' harmonic, the time delay between considered signals decreases. This tendency is clear for both of examined subjects. To receive more information about this phenomenon more subjects should be measured and the statistical test should be introduced to calculate the time delay values. The presented noninvasive method might be helpful in the future for measuring the IOP pulse and estimating hemodynamic status of the eye.

5

Assessment of corneal and fatty tissues biomechanical response in dynamic tonometry tests by using inverse models

71%

Jannesari M. , Kadkhodaei M. , Mosaddegh P. , Kasprzak H. , Behrouz M. J.

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tom Vol. 20, no. 1

39--48

EN

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.

6

High concentrations of excised oxidative DNA lesions in human cerebrospinal fluid

61%

Rozalski R. , Winkler P. , Gackowski D. , Paciorek T. , Kasprzak H. , Olinski R.

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nr Supplement 1