The retina is the fundamental component of vision as it contains the photoreceptors, specialised cells which convert light stimuli into electrical signals, and which represent the first stage of the visual process. The electroretinogram (ERG) is a functional test widely used in clinical practice to help diagnose diseases of the retina and optic nerve. In fact, it measures the electrical response to a light stimulus of retinal cells and different ERG tests can be used to probe different retinal areas and cells. The purpose of this thesis is to build a stimulus source for electroretinography that is capable of presenting an arbitrary pattern of pixels to the entire visual field of a test subject, thus bringing together the functionalities of the existing stimulators. The project was developed at the UIC Neural Engineering Vision Laboratory, during the PoliMi-UIC Master of Science program. The design was developed for the entire device, while only the central part of it was prototyped and tested, as proof of concepts. Luminance uniformity of the device was analysed and the concern about the 32 % luminance variation across the pixels of a previously developed prototype was largely overcome. Considering the colour channel of greatest interest for pERG protocol, the contrast between black and white checks was much higher than the minimum 80 % required by the standards, for all the definitions of contrast used. Finally, the prototyped device was able to elicit consistent flicker ERG and full-field ERG responses in a healthy volunteer subject.
La retina è il componente fondamentale della visione in quanto contiene i fotorecettori, cellule specializzate che convertono gli stimoli luminosi in segnali elettrici e che rappresentano il primo stadio del processo visivo. L'elettroretinogramma (ERG) è un test funzionale ampiamente utilizzato nella pratica clinica per aiutare a diagnosticare malattie della retina e del nervo ottico. Infatti esso misura la risposta elettrica ad uno stimolo luminoso delle cellule della retina e tipi differenti di ERG possono essere utilizzati per sondare diverse aree e cellule della retina. Lo scopo di questa tesi è quello di costruire un nuovo stimolatore per elettroretinografia che sia in grado di presentare un pattern arbitrario di pixel all'intero campo visivo di un soggetto di test, unendo così le funzionalità degli stimolatori esistenti. Il progetto è stato sviluppato presso il Neural Engineering Vision Laboratory della UIC, durante il programma di master PoliMi-UIC. Il design è stato progettato per l'intero dispositivo, mentre solo la parte centrale è stata prototipata e testata, come prova di fattibilità. L'uniformità di luminanza del dispositivo è stata analizzata, superando ampiamente la preoccupazione a proposito della variazione del 32 % nei pixel del prototipo precedentemente sviluppato. Considerando il canale di colore di maggiore interesse per il protocollo pERG, per tutte le definizioni di contrasto utilizzate il contrasto tra bianco e nero è stato molto più elevato del minimo 80 % richiesto dagli standard. Infine, il dispositivo prototipato è stato in grado di evocare in un soggetto volontario sano risposte consistenti sia al flicker ERG che al full-field ERG.
Analysis, design, and testing of a configurable full-field stimulus source for electroretinography
CROCIONI, GIULIA
2018/2019
Abstract
The retina is the fundamental component of vision as it contains the photoreceptors, specialised cells which convert light stimuli into electrical signals, and which represent the first stage of the visual process. The electroretinogram (ERG) is a functional test widely used in clinical practice to help diagnose diseases of the retina and optic nerve. In fact, it measures the electrical response to a light stimulus of retinal cells and different ERG tests can be used to probe different retinal areas and cells. The purpose of this thesis is to build a stimulus source for electroretinography that is capable of presenting an arbitrary pattern of pixels to the entire visual field of a test subject, thus bringing together the functionalities of the existing stimulators. The project was developed at the UIC Neural Engineering Vision Laboratory, during the PoliMi-UIC Master of Science program. The design was developed for the entire device, while only the central part of it was prototyped and tested, as proof of concepts. Luminance uniformity of the device was analysed and the concern about the 32 % luminance variation across the pixels of a previously developed prototype was largely overcome. Considering the colour channel of greatest interest for pERG protocol, the contrast between black and white checks was much higher than the minimum 80 % required by the standards, for all the definitions of contrast used. Finally, the prototyped device was able to elicit consistent flicker ERG and full-field ERG responses in a healthy volunteer subject.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/150545