Document Type

Theses, Ph.D


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Publication Details

Successfully submitted for the award of Doctor of Philosophy (Ph.D) to the Dublin Institute of Technology, 2006.


Background/Aim: Previous research has shown that several clinical conditions cause increased pre-attentive visual search (PAVS) times, implying reduced parallel search capabilities in glaucoma, DLB dementia and Parkinson’s disease. The purpose of the research reported here was two-fold • To examine for the first time the effect of a number of variables on PAVS performance including optical blur, age, retinal eccentricity and perceptual learning. Such investigations are designed to elucidate the nature of best clinical practise and to determine whether the test remains viable in the presence of such potentially confounding variables. • To analyse the efficiency of PAVS in cases of established glaucoma: glaucoma suspects and age –matched normals. Such an investigation is designed to determine the differential diagnostic capacity of the current test and to provide diagnostic cut-off performance indices to facilitate clinical categorisation of patients Methods: Suitably configured flicker, motion displacement and orientation pop-out stimuli were presented to subjects on a computer monitor. The subjects’ task was to accurately locate the pop-out target from among 120 distractors on either left or right of the monitor as rapidly as possible. PAVS performance was determined through analysis of the speed of accurate target location and its relation to the individuals’ complex (non-preattentive) reaction time. Results: The current test remains largely resistant to the sensory degradation effects of optical blur and retinal eccentricity. Only the orientation task requires a reasonable level of visual acuity (better than 6/18). The perceptual learning effect is minimal, therefore little practice is required prior to clinical application of the test. The sensory and motor effects of age are rendered negligible through the development of a measure of perceptual search ability. The test therefore remains clinically robust. In relation to glaucomatous neuropathy, the test yields consistently high sensitivity and specificity for each task and thus appears to provide a suitable means of glaucoma detection. Conclusions: All investigations thus far indicate that, at the very least, the test provides a simple, rapid and accurate means of screening for the effects of glaucomatous optic neuropathy. Its capacity to differentiate glaucoma from suspects suggests its diagnostic ability extends beyond that achieved by conventional perimetry. Longitudinal analysis should confirm whether this is true.