M.Phil.(Optometry) / The concept of contact lenses was conceived over 500 years ago and has now evolved into a fundamental component of optometric practice. Soft contact lenses have become a convenient, aesthetically pleasing and comfortable alternative to spectacles that are becoming increasingly popular. The use of rigid contact lenses is imperative in the management of conditions such as keratoconus due to spectacles being insufficient in providing adequate vision. Placing a contact lens onto the cornea is an invasive procedure. The contact lens is a foreign body to the eye hence it is expected that the eye would react to that foreign body. Literature has revealed that the general reactions of the eye to contact lens wear are initial tearing, alteration of the tear layer and oedema due to reduced oxygen transmission but these are just a few of the known consequences amongst the multitude of the unknown consequences. What exactly goes on under a contact lens remains an enigma which contact lens researchers have strived to uncover over the past century. The consequence of contact lens wear is a vast area of research and can best be investigated by focusing on one aspect at a time. The aim of this study was to use dioptric power matrices and multivariate statistics to explore the effects of both gas permeable and gas non-permeable rigid contact lenses on corneal curvature. This study involves auto-keratometric measurements of the corneal curvature before and after lens wear to establish if there are any curvature changes induced by the contact lens. Keratometric data was collected with an automated keratometer (Nidek ARK-700) and was analysed correctly and completely using multivariate statistics. This thesis presents the findings of a study done in an effort to establish the short-term effects of rigid contact lens wear on keratometric behaviour by using complete methods of multivariate statistical analysis. Twenty four subjects were equally divided into three groups. One group wore polymethyl methacrylate (PMMA) rigid lenses, another group wore rigid gas permeable (RGP) contact lenses and the third group served as the control. The control group was included in the study to establish a reference for normal diurnal changes in keratometric behaviour. Fifty autoii keratometric measurements were taken before and immediately after three hours of rigid contact lens wear for the experimental groups and 50 auto-keratometric measurements were taken before and immediately after three hours of no lens wear for the control group. Data collected was analysed using multivariate statistical methods that in the past have been used infrequently in this area of research.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:7737 |
| Date | 17 September 2013 |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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