Optometry and Vision Sciences - Theses

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    Ageing effects on ocular blood flow, oxygen tension and function during IOP elevation
    Lim, Jeremiah Kah Heng ( 2012)
    This is the first study to simultaneously measure electroretinography, ocular blood flow, and oxygen tension during intraocular pressure elevation. By doing so it shows that changes in oxygen tension are more closely related to function than blood flow. Moreover, by comparing these parameters in young and older eyes this study shows that older eyes have less oxygen availability with higher intraocular pressure despite having similar function. This argues that older eyes use more oxygen to sustain normal function.
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    Time course of retinal changes in models of chronic IOP elevation
    Hui, Flora ( 2010)
    Glaucoma is an increasingly common sight threatening disease. Our understanding of the pathogenesis requires good models for disease risk factors. This thesis refines models of chronic intraocular pressure elevation in rats. Non-invasive assessment showed evidence of widespread retinal dysfunction. It is clear that dysfunction was not solely determined by intraocular pressure, but is associated with either ocular trauma or agent toxicity. Clear methodological recommendations are provided to minimise widespread damage and thus provide improved models for understanding glaucoma.
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    Exploring the mechanisms of Rarebit perimetry
    Hackett, Deborah Anne ( 2009)
    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).