Optometry and Vision Sciences - Theses

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Type: Masters Research thesis × Start date: 1980 × End date: 1999 ×

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    The mobility performance of people with Retinitis pigmentosa as a function of residual vision and psychological variables
    Haymes, Sharon Ann ( 1996)
    The purpose of this investigation was to explain the difference in the mobility performance of people who have retinitis pigmentosa (RP). I proposed that while the difference in performance is chiefly explained by differences in the amount of residual vision, psychological variables are also relevant. I measured the mobility performance of a group of eighteen subjects with RP on three real-world courses using Percentage Preferred Walking Speed (PPWS). I investigated the importance of residual vision using clinical measures of visual acuity, contrast sensitivity and residual visual field. In addition, I investigated the importance of psychological variables, such as anxiety, depression, self-esteem, locus of control and intelligence. I found a highly significant correlation between each of the vision variables and mobility performance. However, contrary to expectations derived from reading the literature, I did not find a significant correlation between psychological variables and mobility performance. I obtained the strongest correlation for a new measure of the residual visual field; the RP Concentric Field Rating. I was able to find a clinically useful model that explained 64% of the variance in functional mobility performance. The model incorporates the RP Concentric Field Rating and the Pelli-Robson measure of peak contrast sensitivity.
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    Changes in selected physiological parameters of the human cornea with age
    Horton, Peregrine ( 1989)
    The effects of age on corneal oxygen flux and the corneal oedema response to contact lens induced hypoxia were studied by comparing the measurements of these variables made on two subject groups of differing ages. No significant difference in corneal oxygen flux between the groups was detected, although a trend towards a decrease in oxygen flux with age was found. A difference was detected, however, in the amount of corneal oedema which occurred in response to eye closure, both in the presence of a thick hydrogel contact lens, which caused corneal hypoxia, and without a lens, with older corneas swelling significantly more than those of the younger group. The implications of this finding for the clinical management of contact lens wearers are discussed. These findings are of particular relevance to the fitting of extended wear lenses to elderly patients, as they cast doubt on the criteria commonly used to determine "acceptable" levels of corneal oedema during lens wear. An attempt was also made to correlate several aspects of corneal structure and physiology with age and each other. A significant difference in the thickness of the corneal epithelium was found to exist between central and peripheral locations - a previously unreported phenomenon. A mathematical model was constructed, relating the various corneal parameters measured.