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The investigation of the thermal effect of contact lens wear

Nishimura, Sachiko 2015. The investigation of the thermal effect of contact lens wear. MPhil Thesis, Cardiff University.
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Since their introduction over 70 years ago, corneal contact lenses have continued to be improved in design and are safely used all over the world. Nevertheless, there is still some risk of infection, especially in soft contact lens (SCL) wearers. In comparison, rigid gas permeable lenses are less likely to cause a serious eye disease than SCL, including both traditional and silicone hydrogel lenses (SiHCL). Two possible reasons for this may be the difference in the tear exchange rate beneath the lens while on the eye, and the influence of lens material on the ocular surface temperature (OST) during the lens wear. This thesis investigates these two factors. Firstly, an in vitro model of the ocular surface was developed to investigate the effect of lens thermal conductivity amongst lens types, and the effect of the existence of the tear film on any subsequent temperature change. The experiment confirmed the successful use of an infrared camera to measure OST change, and also found that the tear film and the water content of the lens were factors in the OST over a lens surface. Secondly, the effect of the tear film on the OST was examined in human eyes. This study confirmed the in vitro study results and the importance of replenishing the lens water content and limiting tear evaporation. Finally, the dynamic changes in OST during lens wear were recorded with different lens types. The OST was measured at the central and peripheral lens, and the conjunctiva. This is the first study to compare the effect of RGP and SCL wear on OST in the same subjects. Once again, similar results emphasising the importance of tear exchange and water content were found, but no effect from tear exchange beneath the lens was observed. In summary, this thesis presents important findings about the influence of both the quality of the tear film and the type of contact lens on the OST. Also it demonstrated the usefulness of ocular thermography to investigate ocular surface changes during lens wear non-invasively

Item Type: Thesis (MPhil)
Status: Unpublished
Schools: Optometry and Vision Sciences
Subjects: R Medicine > RE Ophthalmology
Uncontrolled Keywords: Contact lens, Thermography, Temperature, Tear film
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:56

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