Some Aspects of the Design and Ocular Response to Synthetic Hydrogel Contact Lenses Intended for Continuous Usage

Abstract

Placing a hydrogel contact lens over the invivo cornea creates a new environment for the cornea. Supply of glucose and other metabolites via the anterior chamber remains unaltered, as does the efflux of carbon dioxide. However, the direct access of dissolved atmospheric oxygen to the corneal epithelium is affected. Some physiological constraints on the design of continual (extended) wear contact lenses were reviewed and the theoretical potential of Sauflon T.M. 85, as a continual (extended) wear contact lens was examined. A self-recording, topographic corneal pachometer was constructed and some physiological variations of the in vivo human cornea were investigated using this apparatus. A 20-week comparative clinical study was embarked upon to investigate the ocular response to Sauflon T.M. 85 contact lenses, having firstly established their fitting rationale. Corneal pachometry was adopted as the principal method of investigation during the ocular response study. In addition to this, other factors covering aspects of ocular response, subjective symptoms and contact lens condition were also recorded to draw a more comprehensive picture of the 'eye in extended wear'. The effect of the extended wear of Sauflon T.M. 85 on the diurnal rhythm of the invivo corneal thickness was also examined. In general, the results from this study suggest that the overall ocular response to the continual (extended) wear of Sauflon T.M. 85 lenses is favourable over the 20-week period. However, new queries have arisen about the underlying reasons for some of the observations made. These are discussed along with suggestions and recommendations for further work that needs to be evaluated to increase our present understanding of the human eye in periods of continual (extended) wear of suitable hydrogel contact lenses