Effects of O2 transmissibility on corneal epithelium after daily and extended contact lens wear in rabbit and man.

Abstract

The role of the tear film and its adherence to the underlying ocular surface is dependent on a healthy corneal epithelium. A vital feature of the corneal epithelium is a continuous cycle of renewal and exfoliation as a protective mechanism against injury and invasion of infectious organisms. The corneal epithelial renewal rate is relatively rapid1 and dependent on the homeostatic balance of epithelial proliferation rate, centripetal and vertical cell migration and organized surface cell deletion/exfoliation.2 During daily and overnight contact lens wear, however, normal tear film stability and corneal epithelial surface integrity are compromised, which may lead to minor and occasionally more serious complications such as infectious corneal ulceration. This article discusses the preliminary results of our recent studies on the effects of contact lens oxygen transmissibility, lens type, wearing schedules and non-lens related hypoxia on human and rabbit corneal epithelium. The following outcome measures were assessed: bacterial binding to exfoliated corneal epithelial surface cells, corneal epithelial thickness and surface cell exfoliation in human subjects. Concomitantly, we examined the proliferation rate of the central corneal epithelium, corneal epithelial basal cell turnover rate and corneal epithelial surface cell apoptosis in the standard rabbit model of lens wear.