Dissertations / Theses on the topic 'PentaRay'

Per quanto risulti chiaro come l'innesco della fibrillazione atriale (principalmente parossistica) sia da attribuire a sorgenti focali collocate prevalentemente in prossimità delle vene polmonari (nel 94% dei casi), risulta tutt'ora estremamente dibattuto quali siano i meccanismi di mantenimento di tale anomalia del ritmo cardiaco. Fra le varie teorie riportate in letteratura, una delle più accreditate risulta essere la teoria dei rotori, secondo la quale il mantenimento della FA sarebbe da attribuire a pattern di rotazione spiraliformi, in grado di persistere, come osservato nel celebre studio CONFIRM, per tempi superiori ai 10 minuti. Il presente lavoro di tesi ha quindi l'obiettivo di dare un contributo alla teoria dei rotori, attraverso la realizzazione di mappe di fase ottenute elaborando segnali endocavitari acquisiti durante procedure di ablazione transcatetere con il sistema di mappaggio elettroanatomico CARTO 3 e l'elettrocatetere diagnostico PentaRay, della Biosense Webster. Dopo aver introdotto la fisiopatologia della fibrillazione atriale, soffermandosi particolarmente sulla teoria dei rotori, nel Capitolo 1, e aver introdotto la procedura di ablazione transcatetere, focalizzandosi sull'ausilio del CARTO 3 come sistema di mappaggio real-time, nel Capitolo 2, è stata infatti presentata l'elaborazione eseguita per poter ottenere dai segnali unipolari intracardiaci prelevati, le mappe di fase dalle quali è stata indagata l'eventuale presenza di rotori in 6 pazienti affetti principalmente da FA persistente (Capitolo 3). In conclusione, nell'ultimo capitolo è stata eseguita un'analisi dei risultati, valutando non solamente l'eventuale presenza di rotori nelle regioni della camera atriale in cui sono stati maggiormente osservati in letteratura, ma soffermandosi anche sulla validità dell'elettrocatetere Pentaray nell'indagare la dinamica alla base dei pattern di rotazione spiraliformi.

La fibrillation atriale (FA) est l’arythmie cardiaque soutenue la plus fréquemment rencontrée dans la pratique clinique. Pour la traiter, l’ablation par cathéter de zones cardiaques jugées responsables de soutenir l’arythmie est devenue la thérapie la plus utilisée. Un nouveau protocole d’ablation se base sur l’identification des zones atriales où les électrogrammes (EGM) enregistrés à l’aide d’un cathéter à électrodes multiples, appelé PentaRay, manifestent des décalages spatiotemporels significatifs sur plusieurs voies adjacentes. Ce phénomène est appelé dispersion spatio-temporelle (DST). L’intervention devient ainsi plus adaptée aux spécificités de chaque patient et elle atteint un taux de succès procédural de 95%. Cependant, à l’heure actuelle les zones de DST sont identifiées de manière visuelle par le spécialiste pratiquant l’ablation. Cette thèse vise à identifier automatiquement les sites potentiels d’ablation basée sur la DST à l’aide de techniques d’apprentissage statistique et notamment d’apprentissage profond adaptées. Dans la première partie, les enregistrements EGM sont classés par catégorie en DST vs. non-DST. Cependant, le rapport très déséquilibré entre les données issues des deux classes dégrade les résultats de classification. Nous abordons ce problème en utilisant des techniques d’augmentation de données adaptées à la problématique médicale et qui permettent d’obtenir de bons taux de classification. La performance globale s’élève ainsi atteignant des valeurs de précision et d’aire sous la courbe ROC autour de 90%. Deux approches sont ensuite comparées, l’ingénierie des caractéristiques et l’extraction automatique de ces caractéristiques par apprentissage statistique à partir d’une série temporelle, appelée valeur absolue de tension maximale aux branches du PentRay (VAVp). Les résultats montrent que la classification supervisée de VAVp est prometteuse avec des valeurs de précision, sensibilité et spécificité autour de 90%. Ensuite, la classification des enregistrements EGM bruts est effectuée à l’aide de plusieurs outils d’apprentissage statistique. Une première approche consiste à étudier les circuits arithmétiques à convolution pour leur intérêt théorique prometteur, mais les expériences sur des données synthétiques sont infructueuses. Enfin, nous investiguons des outils d’apprentissage supervisé plus conventionnels comme les réseaux de neurones convolutifs (RNC). Nous concevons une sélection de représentation des données adaptées à différents algorithmes de classification. Ces modèles sont ensuite évalués en termes de performance et coût de calcul. L’apprentissage profond par transfert est aussi étudié. La meilleure performance est obtenue avec un RNC peu profond pour la classification des matrices EGM brutes, atteignant 94% de précision et d’aire sous la courbe ROC en plus d’un score F1 de 60%. Dans la deuxième partie, les enregistrements EGM acquis pendant la cartographie sont étiquetés ablatés vs. non-ablatés en fonction de leur proximité par rapport aux sites d’ablation, puis classés dans les mêmes catégories. Les annotations de dispersion sont aussi prises en compte comme une probabilité à priori dans la classification. La meilleure performance représente un score F1 de 76%. L’agrégation de l’étiquette DST ne permet pas d’améliorer les performances du modèle. Globalement, ce travail fait partie des premières tentatives d’application de l’analyse statistique et d’outils d’apprentissage pour l’identification automatique et réussie des zones d’ablation en se basant sur la DST. En fournissant aux cardiologues interventionnels un outil intelligent, objectif et déployé en temps réel qui permet la caractérisation de la dispersion spatiotemporelle, notre solution permet d’améliorer potentiellement l’efficacité de la thérapie personnalisée d’ablation par cathéter de la FA persistante
Catheter ablation is increasingly used to treat atrial fibrillation (AF), the most common sustained cardiac arrhythmia encountered in clinical practice. A recent patient-tailored AF ablation therapy, giving 95% of procedural success rate, is based on the use of a multipolar mapping catheter called PentaRay. It targets areas of spatiotemporal dispersion (STD) in the atria as potential AF drivers. STD stands for a delay of the cardiac activation observed in intracardiac electrograms (EGMs) across contiguous leads.In practice, interventional cardiologists localize STD sites visually using the PentaRay multipolar mapping catheter. This thesis aims to automatically characterize and identify ablation sites in STD-based ablation of persistent AF using machine learning (ML) including deep learning (DL) techniques. In the first part, EGM recordings are classified into STD vs. non-STD groups. However, highly imbalanced dataset ratio hampers the classification performance. We tackle this issue by using adapted data augmentation techniques that help achieve good classification. The overall performance is high with values of accuracy and AUC around 90%. First, two approaches are benchmarked, feature engineering and automatic feature extraction from a time series, called maximal voltage absolute values at any of the bipoles (VAVp). Statistical features are extracted and fed to ML classifiers but no important dissimilarity is obtained between STD and non-STD categories. Results show that the supervised classification of raw VAVp time series itself into the same categories is promising with values of accuracy, AUC, sensi-tivity and specificity around 90%. Second, the classification of raw multichannel EGM recordings is performed. Shallow convolutional arithmetic circuits are investigated for their promising theoretical interest but experimental results on synthetic data are unsuccessful. Then, we move forward to more conventional supervised ML tools. We design a selection of data representations adapted to different ML and DL models, and benchmark their performance in terms of classification and computational cost. Transfer learning is also assessed. The best performance is achieved with a convolutional neural network (CNN) model for classifying raw EGM matrices. The average performance over cross-validation reaches 94% of accuracy and AUC added to an F1-score of 60%. In the second part, EGM recordings acquired during mapping are labeled ablated vs. non-ablated according to their proximity to the ablation sites then classified into the same categories. STD labels, previously defined by interventional cardiologists at the ablation procedure, are also aggregated as a prior probability in the classification task.Classification results on the test set show that a shallow CNN gives the best performance with an F1-score of 76%. Aggregating STD label does not help improve the model’s performance. Overall, this work is among the first attempts at the application of statistical analysis and ML tools to automatically identify successful ablation areas in STD-based ablation. By providing interventional cardiologists with a real-time objective measure of STD, the proposed solution offers the potential to improve the efficiency and effectiveness of this fully patient-tailored catheter ablation approach for treating persistent AF

Dissertação Apresentada para Obtenção do Grau de Mestre em Engenharia Biomédica
Neste trabalho realizou-se um estudo clínico conducente à obtenção duma relação entre a densidade óptica do cristalino e os parâmetros fluxo, vácuo e potência de ultra-sons, utilizados na cirurgia da catarata – facoemulsificação – de forma a adequar este procedimento cirúrgico a cada patologia de catarata. Para tal, foi utilizado o sistema de diagnóstico oftalmológico Pentacam, para se mediram as densidades ópticas a 23 pacientes e classificar cada catarata em graus através de dois sistemas de classificação: o LOCS III, que classifica as cataratas numa escala de 0 a 6, segundo o tom de cor do núcleo do cristalino, e o PNS, o qual, consoante o valor da densidade óptica do núcleo do cristalino, classifica as cataratas numa escala de 0 a 5. Feita a classificação, obteve-se a relação entre a densidade óptica e os graus da catarata, dos dois sistemas de classificação, que, por sua vez, foram relacionados com os parâmetros da facoemulsificação. Na sequência da classificação das cataratas em graus, não se verificou uma relação entre os valores de densidade óptica e os graus da catarata do sistema LOCS III; enquanto para o sistema PNS constatou-se uma relação linear crescente, até ao Grau 3. A partir deste grau não foi possível tirarem-se conclusões, uma vez que não se obtiveram casos clínicos para os graus 4 e 5. Relativamente à análise da densidade óptica com os parâmetros da facoemulsificação, verificou-se que a densidade aumenta com a diminuição do fluxo e do vácuo, considerando a potência de ultra-sons a mesma para todos os graus. O facto de não se ter observado uma dependência entre a densidade óptica e os graus da catarata do sistema LOCS III, possibilitou concluir que a densidade óptica e a cor do cristalino são métodos diferentes de avaliação da catarata, sendo que um aumento da densidade óptica não implica um tom mais escuro do núcleo do cristalino. Como consequência, conclui-se, de igual modo, que o sistema LOCS III é um método subjectivo, ao passo que o sistema PNS demonstra ser um método mais objectivo. Relativamente ao estudo sobre a facoemulsificação, este mostrou que os valores de fluxo e de vácuo diminuem com o aumento da densidade óptica do cristalino. Tal facto revela ser possível a extracção das cataratas minimizando-se o uso dos ultra-sons, evitando, assim, danos nas estruturas oculares. Acresce-se ainda a esta análise que, quando usado o sistema LOCS III no diagnóstico e avaliação das cataratas, as pupilas devem estar dilatas, no sentido de os valores dos parâmetros da facoemulsificação serem os mais correctos para a avaliação de cada caso clínico.

Polyarene dendrimers are composed entirely of aromatic rings and are of interest as they possess rigid and shape-persistent structures, which have potential applications in materials chemistry and as scaffold for functional molecules. This thesis describes the synthesis and characterisation of a number of new polyarene dendrimers containing pentaphenylbenzene-like (pentaaryl dendrimers) and hexaphenylbenzene-like (hexaaryl dendrimers) branching units which are capable of focal and peripheral expansions. These structures are based on terminal and internal 1,3-dialkyne cores, onto which two polyaryl sections were introduced via Diels-Alder reaction. These compounds possess inherent axial chirality as a result of the dialkyne position on the core, and a range of differently substituted polyaryl units which result in further chiral axes. Several crystal structures of pentaryl dendrimers were obtained, with these crystallising either as meso conformers or conformers with C2 symmetry. Introduction of a chiral auxiliary onto the central aromatic ring of these dendrimers provided evidence of the atropisomers in solution. These were studied via VT 13C NMR, revealing fast rotation and an energy barrier of about 66 kJ mol-1. The presence of additional aromatic rings on a hexaaryl dendrimer enabled observation of atropisomerism in solution owing to the greater steric hindrance of rotation of its branching units about the chiral axes. Fluorine-containing analogues of these dendrimers were synthesised and subjected to conformational studies through 19F-19F Exchange Spectroscopy (EXSY). Qualitative and quantitative analysis of the spectra revealed the kinetic and thermodynamic parameters, showing that the energy barrier of rotation of these dendrimers was within the range of 75-80 kJ mol-1, which was sufficient for spectroscopic observation but not for physical separation. Polyaryls with symmetry or lacking symmetry have been synthesised. The lack of symmetry was achieved by stepwise introduction of the polyaryl fragments. This demonstrates a route to polyaryls with sections possessing different structural features and thus potentially engineered properties and future chemical differentiations.

Jag arbetar med frodiga och pompösa skulpturer som är tillverkade i keramik. Projektet Black Mass har musikgenren BlackMetal som utgångspunkt. Här undersöker jag hur musikgenren Black Metal går att överföra till keramik. Den krock mellankeramik och Black Metal tar sin form i en fiktiv ritual där ambitionen varit att utgå från musiken som beskriver ondska, mörkeroch satanism. I min essä förklarar jag min bakgrund till musik genren och hur det kommer sig att jag valde Black Metal somutgångspunkt till mina keramiska verk. Jag beskriver mitt förhållande till leran och varför den blivit mitt huvudsakliga medium imin konstnärliga praktik. Sedan har jag försökt bena ut vad det är inom genren/subkulturen Black Metal som jag velat ta tillvarapå och införliva i min installation ”Black Mass”.

Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains viii, 222 p.; also includes graphics Includes bibliographical references (p. 214-222). Available online via OhioLINK's ETD Center

This work aims to improve the predictability of asphericity and average keratometry in keratoconus patients after implantation of intrastromal corneal ring segments (ICRS) by creating computational models based on machine learning, using tomographic data of the cornea. This study included 209 eyes of 160 keratoconus (grades I, II and III) implanted with ICRS. The Ferrara ICRS with 160 degrees of arch was implanted in all patients. The ICRS thickness varied from 150 to 250 micra. One or two segments were implanted. The base was composed of corneal tomography Pentacam® (Oculus, Wetzlar, Alemanha) parameters, clinical data and Ferrara ring data totaling 39 parameters. To create the models, neural network algorithms type multlayer perceptron (MLP) and linear regression were used. This study was conducted in four phases: (1) Preparation of the database and setting the values to be predicted mean keratometry and asphericity; (2) Calculation of the variation mean keratometry and asphericity and the nomogram calculation error; (3) Application of machine learning algorithms and attribute selection; (4) Mean keratometry and asphericity variation calculation provided for comparing algorithm with the variation of the preoperative and postoperative calculation of the algorithm and of the error. As a result, the best mean absolute error value found for asphericity was 0.19 and mean keratometry was 1.18. Comparing the mean absolute error values of the nomogram and the average absolute error of the algorithm, there was an improvement of 0.11 to asphericity and 0.09 to mean keratometry in relation to the current nomogram, confirming that the use of computational models can achieve more accurate results may contribute to surgical decision in an attempt to improve the quality of vision of keratoconus patients.
O presente trabalho destina-se a melhorar a previsibilidade da asfericidade e da ceratometria média no pós-operatório de implante de anel intraestromal (SAIC) em pacientes com ceratocone por meio da criação de modelos computacionais baseados em aprendizagem de máquina, utilizando dados tomográficos da córnea. Foram incluídos 209 olhos de 160 pacientes com graus I, II e III de ceratocone submetidos a cirurgia com implante de SAIC. Em todos os pacientes foi implantado anel de Ferrara com 160o de arco com variação de espessura entre 150 e 250 µm e presença de 1 ou 2 segmentos. A base foi composta por parâmetros da tomografia de córnea pentacam®, dados clínicos e dados do anel de Ferrara totalizando 39 parâmetros. Para criação dos modelos, foram utilizados os algoritmos Rede Neural do tipo multlayer perceptron (MLP) e regressão linear. Este estudo foi desenvolvido em 4 fases distintas: (1) Preparação da base de dados e definição dos valores a serem preditos de ceratometria média e asfericidade; (2) Cálculo da variação da ceratometria média e asfericidade e cálculo do erro do nomograma; (3) Aplicação dos algoritmos de aprendizagem de máquina e seleção de atributos; (4) Cálculo da variação da ceratometria média e da asfericidade prevista pelo algoritmo comparando com a variação do pré e pós operatório e cálculo do erro do algoritmo. Como resultado, o melhor valor do erro absoluto médio encontrado para asfericidade foi 0.19 e para ceratometria média foi 1.18. Comparando os valores do erro médio do nomograma e o erro médio do algoritmo, houve uma melhora de 0.11 para asfericidade e 0.09 para ceratometria média em relação ao nomograma atual, confirmando que a utilização de modelos computacionais é capaz de alcançar resultados mais precisos podendo contribuir para decisão cirúrgica na tentativa de melhorar a qualidade de visão de pacientes com ceratocone.

Esse trabalho visa a investigar a estrutura bi-Hamiltoniana de uma classe de sistemas dinâmicos. Depois de introduzir as ferramentas necessárias, a saber, as noções de variedade de Poisson, de grupo de PoissonLieedenetworknodiscoenoanêl,introduziremosossistemasdinâmicos relevantes nessa dissertação, chamados de reticulados de Coxeter-Toda. Esses sistemas dinâmicos, cujo espaço de fase pode ser identicado com umoportunoquocientedeumacéluladupladeCoxeter-Bruhatdogrupo linear geral, são obtidos por redução do sistema de Toda em GLn. Na parte nal do presente trabalho apresentaremos alguns resultados relacionado à um sistema dinâmico discreto chamado de aplicação do pentagrama, o qual pode ser obtido através uma oportuna discretização do sistema dinâmico de Boussinesq.
This work aims to study the bi-Hamiltonian structure of a class of dynamical systems. After introducing the relevant tools, namely the notions of Poisson manifold, Poisson-Lie group and of network dened in a disc and in an annulus, we will introduce the dynamical systems of interest for this dissertation, i.e., the Coxeter-Toda lattices. These dynamical systems, whose phase-space can be identied with a suitable quotient of a Coxeter double Bruhat cell of the general linear group, are obtained by reduction starting from the Toda ow on GLn. In the nal part of the present work will be presented some results concerning a discrete integrable system close to the so called Pentagram map, which is a discretization of the Boussinesq dynamical system..

Online basierte Lernplattformen sind an Universitäten und Hochschulen im Bereich der Lehre weitestgehend eingeführt. An Schulen werden diese Lernplattformen ebenfalls immer mehr genutzt. Bei der Nutzung von online basierten Lernplattformen verspricht man sich eine Reihe von Verbesserungen im Bereich der Selbstlernkompetenzen. In der vorliegenden Arbeit wird untersucht, in welcher Form Lernangebote auf der Basis von Lernplattformen über das Internet für Schüler bereitgestellt werden können und welche Konsequenzen sich für den Aufbau der Lernplattformen ergeben, wenn diese in der Schule eingesetzt werden. Parallel hierzu wird untersucht, wie stark sich die Selbstlernkompetenz der Schüler während der Nutzung von online basierten Lernplattformen verändert. Damit eine Zuordnung der entwickelten Szenarien zu den jeweiligen Lernplattformen vereinfacht wird, wurde ein Diagramm in der Form eines Fünfeckes entwickelt. Dieses Diagramm wird als didaktisches Pentagramm in der Arbeit eingeführt und verwendet. Bei der Nutzung der Lernplattformen wird die Möglichkeit der Kollaboration zwischen den Nutzern (Lehrende und Lerner) als Klassifikationskriterium aus der Sicht eines Lerners eingeführt. Daraus ergeben sich zwei Typen von Lernplattformen: - Primär kollaborative Systeme (PKS) bzw. Gruppenlernsysteme, bei denen die Kollaboration einen wesentlichen Bestandteil des Wissenserwerbs darstellt und - Sekundär kollaborative Systeme (SKS) bzw. Individuallernsysteme, bei denen eine Kollaboration mit anderen Lernern in den Hintergrund rückt. Der Einsatz der Lernplattformen wird zum einen durch einen Fragebogen zum anderen durch die Messung der Leistungsentwicklung im Vergleich zu Testgruppen ohne die Nutzung von online basierten Lernplattformen erfasst. Aus diesen Ergebnissen heraus werden allgemeine technische Anforderungen an Lernplattformen abgeleitet. Durch die Umsetzung dieser Forderungen soll sichergestellt werden, dass bei einem Einsatz der Lernplattformen im schulischen Bereich ein optimaler Lernerfolg erreicht werden kann. Es wird nachgewiesen, dass für Einsatz von online basierten Lernplattformen bei Lernern mit einer gering ausgeprägten Selbstlernkompetenz eine Steuerung des Lernweges notwendig ist. In diesem Fall führt der Einsatz von online basierten Lernplattformen des Types SKS zu einer Verbesserung der Lernleistung. Der kollaborative Ansatz unter Nutzung eines primär kollaborativen Systems bzw. Gruppenlernsystems führt bei den Testgruppen zwar zu einer Verbesserung der Selbstlernkompetenz, hierbei können jedoch keine Verbesserungen von Lernleistungen gegenüber dem klassischen Lehransatz nachgewiesen werden. ---- <img src="http://vg01.met.vgwort.de/na/532892aa69654092b591f5531a8bf22c" width="1" height="1" alt=""/>

Online basierte Lernplattformen sind an Universitäten und Hochschulen im Bereich der Lehre weitestgehend eingeführt. An Schulen werden diese Lernplattformen ebenfalls immer mehr genutzt. Bei der Nutzung von online basierten Lernplattformen verspricht man sich eine Reihe von Verbesserungen im Bereich der Selbstlernkompetenzen. In der vorliegenden Arbeit wird untersucht, in welcher Form Lernangebote auf der Basis von Lernplattformen über das Internet für Schüler bereitgestellt werden können und welche Konsequenzen sich für den Aufbau der Lernplattformen ergeben, wenn diese in der Schule eingesetzt werden. Parallel hierzu wird untersucht, wie stark sich die Selbstlernkompetenz der Schüler während der Nutzung von online basierten Lernplattformen verändert. Damit eine Zuordnung der entwickelten Szenarien zu den jeweiligen Lernplattformen vereinfacht wird, wurde ein Diagramm in der Form eines Fünfeckes entwickelt. Dieses Diagramm wird als didaktisches Pentagramm in der Arbeit eingeführt und verwendet. Bei der Nutzung der Lernplattformen wird die Möglichkeit der Kollaboration zwischen den Nutzern (Lehrende und Lerner) als Klassifikationskriterium aus der Sicht eines Lerners eingeführt. Daraus ergeben sich zwei Typen von Lernplattformen: - Primär kollaborative Systeme (PKS) bzw. Gruppenlernsysteme, bei denen die Kollaboration einen wesentlichen Bestandteil des Wissenserwerbs darstellt und - Sekundär kollaborative Systeme (SKS) bzw. Individuallernsysteme, bei denen eine Kollaboration mit anderen Lernern in den Hintergrund rückt. Der Einsatz der Lernplattformen wird zum einen durch einen Fragebogen zum anderen durch die Messung der Leistungsentwicklung im Vergleich zu Testgruppen ohne die Nutzung von online basierten Lernplattformen erfasst. Aus diesen Ergebnissen heraus werden allgemeine technische Anforderungen an Lernplattformen abgeleitet. Durch die Umsetzung dieser Forderungen soll sichergestellt werden, dass bei einem Einsatz der Lernplattformen im schulischen Bereich ein optimaler Lernerfolg erreicht werden kann. Es wird nachgewiesen, dass für Einsatz von online basierten Lernplattformen bei Lernern mit einer gering ausgeprägten Selbstlernkompetenz eine Steuerung des Lernweges notwendig ist. In diesem Fall führt der Einsatz von online basierten Lernplattformen des Types SKS zu einer Verbesserung der Lernleistung. Der kollaborative Ansatz unter Nutzung eines primär kollaborativen Systems bzw. Gruppenlernsystems führt bei den Testgruppen zwar zu einer Verbesserung der Selbstlernkompetenz, hierbei können jedoch keine Verbesserungen von Lernleistungen gegenüber dem klassischen Lehransatz nachgewiesen werden. ---- <img src="http://vg01.met.vgwort.de/na/532892aa69654092b591f5531a8bf22c" width="1" height="1" alt=""/>

Purpose: To determine whether semi-scleral contact lenses (sSCL) can be appropriately fitted using corneal sagittal depth measurements, and to determine the impact of fit on visual acuity, effect of time on topographic corneal clearance and comfort ratings. Method: Three sSCL (Jupiter 15mm; Essilor) were fit to 20 subjects who had previous diagnoses of KC (n=18) or PMD (n=2). The fitting of the sSCL were based on the CSD measured with the Visante™ OCT at a 15mm chord on the horizontal meridian. To select the sSCL from the diagnostic trial lens set, values of 325 (lens 1), 375 (lens 2) and 425 (lens 3) μm were randomly added in sequence to the CSD. Subjects were allowed to wear each of the sSCL for 1hour. After this time, the central corneal clearance (CCC) was assessed using an UL-OCT, high contrast visual acuity (HCVA) and low contrast visual acuity (LCVA) were measured using a LogMAR VA chart and comfort ratings were obtained using a comfort rating scale (0-100). Results: The mean CSD in the horizontal meridian was 3.78±0.53 (range: 3.33-4.17) mm at a 15mm chord. The mean CCC was 190±100, 360±120 and 450±170 µm for each lens respectively (p=0.001). The mean CCC loss was 30.00±40.00, 30±60.00 and 40.00±50 µm for each lens respectively (p>0.05). The mean HCVA for lenses 1, 2 and 3 were 0.05±0.12, 0.07±0.11 and 0.11±0.08 respectively, which were significantly different (p=0.02). Tukey post hoc analysis demonstrated that this difference was only significant between lenses 1 and 3 (p=0.01). Similar findings were found for LCVA. The overall comfort rating for all three sSCL was 77.7±10.6. The comfort ratings for lenses 1, 2 and 3 were 74.9±9.2, 79.7 ±11.6 and 78.6±10.8 respectively. These differences were not significantly different (p=0.24). Conclusion: Evaluation of CSD can be used effectively to select which sSCL to fit on the eye. The results of this study suggest that lens 2 (adding 375 μm to the CSD) gave the best combination of VA and comfort ratings. However, evaluation of the fluorescein pattern must be balanced with the VA and comfort ratings for successful fitting of sSCL in a clinical setting. There was also a likelihood of topographic corneal loss after 1 hour of sSCL wear; however, this may vary depending on many factors such as scleral zone and its relationship with the scleral conjunctiva. Eyelid force, design of the contact lens and other unknown factors may play a part in the contact lens settling time and amount.

Univerzita Karlova 1. lékařská fakulta Studijní program: Zobrazovací metody v lékařství (P5150) Studijní obor: Zobrazovací metody v lékařství (5103V000) MUDr. Adam Kopecký Změny na předním segmentu po 25G+ PPV Changes in the Anterior Segment after 25G+ PPV Abstract Vedoucí závěrečné práce/Školitel: doc. MUDr. Jiří Pašta, CSc., FEBO Praha, 2019 Abstract: Pars plana vitrectomy is a dominant surgical method in posterior segment surgery of the eye. The principle of this method is the surgical approach via the pars plana anatomical region. With this approach, surgeon performs the posterior segment surgery without directly affecting the anterior segment of the eye. Short-term effect of pars plana vitrectomy on the anterior segment of the eye has been repeatedly proven. That might be an important factor both in assessing the complications of this method and planning the surgery in complicated patients. Generally, it is presumed that we do not observe long-term effects on anterior segment after pars plana vitrectomy. The aim of our work is to evaluate the long-term changes in the anterior segment after the uncomplicated 25G + PPV with gas tamponde. The group of 20 patients was selected according to strict indication criteria. Using a series of examinations, we examined specific parameters such as: intraocular...