Optometry and Vision Sciences - Theses

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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.