A virtual environment for modeling and analysis of human eye

The aim of this work is to develop a virtual environment for modelling and analyse individual virtual eyes which are able to integrate the modern imaging techniques input data. This environment is realized in 3D CAD software by means of specific plug-ins. The tools for analysing the virtual eye are based on ray-tracing and curvature analysis, while the shape of the eye is represented by NURBS or mesh surfaces. This thesis develops, and validates the use of, the plug-ins for the modelization of virtual eyes inside a 3D CAD environment; in particular a novel lens model whose shape is linked to geometrical and optical constraints was created. Shape was also tested on real crystalline images obtained with shadow photogrammetry. Moreover real eye topography was used for modelization of anterior cornea and preliminary results from ray tracing are shown. This model and the ray-tracing tools may be used in future works for design of ophthalmic, contact or intraocular lenses, specifically customised of a single ametropy.Lo scopo di questo lavoro è stato quello di sviluappare un ambiente virtuale per la modellazione e l’analisi di un occhio virtuale personalizzato, che fosse in grado di integrare le moderne tecniche di analisi ottica come dati di ingresso. Questo ambiente è stato sviluppato all’interno di un software CAD tramite l’ultilizzo di plug-in specifici. Gli strumenti utilizzati per analizzare l’occhio virtuale sono basati sul ray-tracing e sull’analisi di curvatura, mentre la geometria dell’occhio è stata modellizzata tramite l’utilizzo di superfici NURBS o mesh. La presente tesi sviluppa, e valida l’utilizzo, di codesti plug-in per la modellizzazione di un occhio virtuale in un ambiente CAD 3D; in particolare è stato creato un modello innovativo di lente, la cui forma è legata a vincoli geometrici ed ottici. La forma di tale lente è stata confrontata con cristallini reali le cui immagini sono state ottenute tramite fotografia ad ombra. Inoltre la topografia di un occho reale è state utilizzata per modellare la superficie anteriore della cornea e sono quindi riportati i risultati preliminari del ray-tracing. Questo modello e gli strumenti di ray-tracing utilizzati potranno essere utilizzati in futuro per la progettazione di lenti oftalmiche, a contatto o intraoculari specificatamente costumizzate sulle esigenze dell’ametrope

Shape modeling and analysis of a human eye based on individual experimental data

The aim of this work is to develop a virtual environment for modeling and analysis an individual virtual eye which is able to integrate the modern imaging techniques as input data. Method: The virtual environment is developed in a 3D CAD by means of specific plug-ins due to the ability of this software to manage freeform surfaces and to the simplicity in the scripts implementation. Result: Spot of confusion analysis has been performed on two virtual eyes, with data derived from literature and by topography measurements. Discussion & Conclusion: Experimental measurements and literature data provide expected results in the spot of confusion analysis

Morfologické detaily v AlN epivrstvách připravených magnetronovým napařováním

The aim of this study is to characterize the surface topography of aluminum nitride (AlN) epilayers prepared by magnetron sputtering using the surface statistical parameters, according to ISO 25178-2:2012. To understand the effect of temperature on the epilayer structure, the surface topography was investigated through atomic force microscopy (AFM). AFM data and analysis of surface statistical parameters indicated the dependence of morphology of the epilayers on their growth conditions. The surface statistical parameters provide important information about surface texture and are useful for manufacturers in developing AlN thin films with improved surface characteristics. These results are also important for understanding the nanoscale phenomena at the contacts between rough surfaces, such as the area of contact, the interfacial separation, and the adhesive and frictional properties.Cílem této studie je charakterizovat topografii povrchu AlN epivrstev připravených pomocí magnetronového napařování. K tomu využíváme statistické parametry povrchu dle normy ISO 25178-2:2012. Abychom pochopili vliv teploty, byla topografie povrchu provedena pomocí AFM mikroskopu. Data z AFM mikroskopu a analýza statistických parametrů povrchu ukazují závislost morfologie epivrstev na podmínkách jejich růstu. Statistické parametry poskytují důležité informace o textuře povrchu a jsou významné pro výrobu tenkých vrstev AlN se zlepšenými charakteristikami povrchu. Tyto výsledky jsou také důležité pro pochopení jevů v nanoměřítku v kontaktních bodech drsných povrchů - oblasti kontaktu, separace rozhraní a o adhesivních a frikčních vlastnostech

Localized cervical cancer (stage <IIB): accuracy of MR imaging in planning less extensive surgery

PURPOSE: This study was undertaken to determine the accuracy of magnetic resonance (MR) imaging in the preoperative staging of patients with clinically localised cervical cancer eligible for less extensive surgery. MATERIALS AND METHODS: Fifty-three patients with biopsy-proven carcinoma of the uterine cervix and eligible for conservative surgery prospectively underwent MR imaging. Images were assessed for tumour site and size, infiltration of the cervical stroma, infiltration of vaginal fornices and relationship between the tumour and the internal os of the endocervical canal and the presence and dimensions of pelvic and lumboaortic lymph nodes (cutoff values 1 cm and 0.5 cm minimum axial diameter). MR imaging data were compared with the histopathological findings. RESULTS: The endocervix was the site of origin of 25% (13/53) of the cervical tumours and the exocervix the site of origin of 75% (40/53). In the assessment of cervical stroma infiltration, there was agreement between MR imaging and histopathology in 75% of cases. MR imaging had 67% sensitivity, 92% specificity and 91% diagnostic accuracy in assessing infiltration of the vaginal fornices. In the evaluation of the infiltration of the internal os, MR imaging had 86% sensitivity, 93% specificity and 92% accuracy. In the assessment of the lymph nodes, when using a cutoff value of 1 cm, MR imaging had a sensitivity, specificity and diagnostic accuracy of 28%, 100% and 89%, respectively. With a cutoff value of 0.5 cm, MR imaging had a sensitivity, specificity and diagnostic accuracy of 33%, 92% and 83%, respectively. CONCLUSIONS: MR imaging had a high level of accuracy in the preoperative assessment of the extent of cervical tumour in patients eligible for conservative surgery. Accuracy is lower in the evaluation of the pelvic and lumboaortic lymph nodes