Rabbit models of contact lens--associated corneal hypoxia: a review of the literature.

Abstract

PURPOSE: To provide a review of the literature on rabbit models of contact lens-associated corneal hypoxia. METHODS: The literature was searched for articles describing corneal hypoxia in the rabbit coincident with contact lens wear. The articles were identified by key word searches for rabbit models, contact lens, hypoxia, and cornea. RESULTS: Designing a rabbit model of contact lens-associated corneal hypoxia requires identification of the key determinants of the physiologic response. The retention of soft contact lenses, particularly high-water content lenses, is problematic in the rabbit eye, in which blink frequency is on the order of minutes. An intact nictitating membrane may be beneficial in the hydration and, therefore, retention of soft contact lenses. Although tarsorrhaphy improves lens retention, lid closure also enhances the hypoxic response and may obscure the benefits of the greater oxygen transmissibility of soft contact lenses. The duration of lens wear in most reviewed studies was 24 hours or less, with only a few studies evaluating the hypoxic effect of lens wear of 1 week or more. Methods commonly used to characterize corneal hypoxia in rabbits include pachymetry, tear film lactate dehydrogenase measurements, clinical observations of limbal hyperemia, and more invasive methods of assessing cell proliferation and apoptosis. In summary, the ideal rabbit model of contact lens-associated corneal hypoxia depends on the question to be answered. CONCLUSIONS: This review tabulates the known studies, highlights key considerations in study design, and describes useful methods in characterization of the hypoxic response.