Nystagmus and eye reflex sensor

Swart, Wayne (2011-12)

Thesis (MScEng)--Stellenbosch University, 2011.

Thesis

ENGLISH ABSTRACT: Nystagmus is an eye movement pattern that consists of a drifting gaze component, known as the slow phase, followed by a corrective quick phase component. The presence of nystagmus or the lack thereof under certain conditions can be used for various diagnostic purposes including the diagnosis of physiological, pathological and neurological conditions. The angular velocity of the quick phase can make the detection of nystagmus a challenging task for the untrained eye, since the quick phases are usually comparable with saccadic eye motions. The goal is thus to develop a fully automated diagnostic tool that can identify the presents of nystagmus in a patient’s eye motions. In this thesis, an appropriate eye tracking method was selected from a number of eye tracking methods that are commonly implemented in the literature. A video-oculography goggle concept was chosen based on criteria such as invasiveness, sampling rate, accuracy and telemedicine capability, amongst other nystagmus related necessities. A binocular video-oculography concept was chosen that satisfied the technical requirements and provided a cost-effective design. An automated analysis algorithm was developed for automatic nystagmus identification from eye motion data. The algorithm was validated by testing the performance of the algorithm on an optokinetic nystagmus signal. It proved to provide a reliable automatic identification of nystagmus beats, even in signals that contained nystagmus as well as random motion components. A statistical analysis showed that the algorithm provided a sensitivity of 91.8% and a specificity of 96.5% for pure nystagmus signals, and a sensitivity and specificity of 87.8% and 91.1% respectively for mixed signals.

AFRIKAANSE OPSOMMING: Nystagmus is ’n oogbewegingspatroon wat bestaan uit ’n dwalende tuurkomponent, wat die stadige fase genoem word, gevolg deur ’n vinnige korrigereringsbeweging wat bekend staan as die vinnige fase. Die teenwoordigheid van nystagmus, of afwesigheid daarvan in sekere gevalle, kan gebruik word in ’n verskeidenheid diagnostiese toepassings, onder andere die diagnose van fisiologiese-, patalogiese- en neurologiese kwale. Die hoeksnelheid van die vinnige fase lei daartoe dat nystagmus dikwels moeilik is om te bespeur vir ongeöefende oë, aangesien dit vergelykbaar is met saccade bewegings. Die doel van hierdie navorsing is dus die ontwikkeling van ’n stelsel wat ’n volledige automatiese identifisering van nystagmus kan behartig. ’n Gepaste oogvolgtegniek was gekies vanuit ’n aantal verskillende oogvolgmetodes wat dikwels in die praktyk gebruik word. Die finale keuse was ’n skermbril, video-oogvolgmetode wat gekies was op grond van kriteria soos onder andere, invallendheid, meetfrekwensie, akkuraatheid en geskiktheid vir telemedisyne toepassings. Die ontwikkelde brilkonsep bied ’n koste-effektiewe oplossing, met die moontlikheid om albei oë te volg en bevredig al die bogenoemde tegniese spesifikasies. ’n Geoutomatiseerde nystagmus identifiseringsalgoritme is ontwikkel. Die algoritme se effektiwiteit is getoets op optokinetiese nystagmusseine. Betroubare resultate is vekry vanaf die algoritme, selfs in die geval van gemengde seine wat bestaan uit arbritrêre- en nystagmus komponente. Statistiese analiese het gewys dat die algoritme ’n sensitiwiteit van 91.8% en ’n spesifisiteit van 96.5% kon behaal vir seine met slegs nystagmus inhoud. Vir gemengde inhoud seine het die algoritme ’n sensitiwiteit van 87.8% en spesifisiteit van 91.1% behaal.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/18019
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