Thesis (doctoral)--Technische Universiteit Eindhoven, 1999. / "SPIE digital library." Originally published: Knegsel : HV Press, 1999. Includes bibliographical references and index. Also available in print version.

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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 39-45). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 43-46). Also available via the Internet.

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Early visual processing is subject to binocular interactions because cells in striate cortex show binocular responses and ocular dominance (Hubel & Weisel, 1968). The work presented in this thesis suggests that these physiological interactions can be revealed in psychophysical experiments using normal human observers. In the region corresponding to the blind spot, where binocular interactions differ from areas of the visual field which are represented by two eyes, monocular contrast sensitivity is increased. This finding can be partially explained by an absence of normal binocular interactions in this location (Chapter 2). A hemianopic patient was studied in an attempt to discover whether the effect in normal observers was mediated by either a mechanism in striate cortex or via a subcortical pathway. However, the results were unable to distinguish between these two explanations (Chapter 3).In a visual search task, no difference in reaction time was observed for targets presented to the region corresponding to the blind spot compared with targets presented to adjacent binocularly represented areas of the visual field. Since performance was unaffected by the monocularity of the region corresponding to the blind, pop-out for orientation may be mediated beyond striate cortex where cells are binocularly balanced (Chapter 5). Further support for this contention was provided by studies of orientation pop-out in central vision which found that dichoptic presentation of stimuli did not affect the degree of pop-out obtained and that in general, visual search for a target based solely on eye of origin is impossible (Chapter 6). However, a task that measured orientation difference sensitivity more directly than the search experiments, found that thresholds were higher for dichoptically presented stimuli. This suggests the involvement of neurons that receive a weighted input from each eye. A model of orientation difference coding can account for the results by assuming that the range of inhibition across which orientation differences are coded is narrower for dichoptic stimuli leading to a greater resolvable orientation difference (Chapter 7).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 46-51). Also available via the Internet.

Thesis (doctoral)--Technische Universiteit Eindhoven, 1999. / Originally published: Knegsel : HV Press, 1999. Includes bibliographical references and index.

Visual field testing, or perimetry, measures peripheral visual loss in eye diseases such as glaucoma. Rarebit Perimetry (RBP) is a new and novel perimetric method, introduced in 2002 by Lars Frisén (2002), with the aim of detecting low degrees of neural damage within the retina. / RBP is unlike conventional perimetric methods that measure levels of retinal sensitivity, but instead uses very bright (i.e. suprathreshold) and very small targets to detect tiny areas of absolute blindness within otherwise normal areas of vision. RBP thus claims to locate miniscule gaps in the receptive field matrix of neurons in the retina, with the assumption that dead neurons leave gaps in this matrix. The most useful application of this idea is to detect progressive eye disease in the earliest stages (Frisén, 2002). Current research shows that RBP correlates with other standard visual field tests (Brusini, Salvetat, et al., 2005; Frisén, 2003; Gedik, Akman, et al., 2007; Martin & Wanger, 2004), but may afford greater sensitivity by detecting very mild visual losses missed by other tests (Martin, Ley, et al., 2004; Martin & Nilsson, 2007; Nilsson, Wendt, et al., 2007). / To date, there are no studies that definitively test the theoretical basis of RBP, so in this thesis I aim to explore the proposed underlying mechanisms and assumptions of this test. In particular, the proposed mechanism of RBP leads to specific predictions as to how responses will alter when the luminances of the RBP targets are systematically decreased. I therefore compared RBP responses of mean hit rate as a function of target luminance and found results to be inconsistent with the proposed RBP mechanism. Mathematical simulations were performed to explore reasons for the differences between the two groups (Chapter Seven).