ARTIFICIAL TEAR SOLUTIONS AND PROTECTION OF THE CORNEAL EPITHELIUM FROM DESICCATION

Desiccation of the ocular surface in dry environments is one of the factors contributing to discomfort in dry eye patients. An in vivo desiccation model was used to test efficacy of artificial tear products for prevention of ocular surface damage during extended desiccating exposure. One drop of an artificial tear or a lens rewetting solution was placed on the eye of an anesthetized rabbit and the eye was held open with a speculum for 2 hr. Desiccated eyes were held open for 2 hr without application of a tear solution. Eyes were stained with 1% methylene blue in BSS. Naïve control eyes were stained with methylene blue without prior desiccation. The percentage of corneal area stained was scored and a 8-mm button of central cornea was extracted in acetone:saturated sodium sulfate (7:3). Absorbance of extracts was measured at 660 nm. Extract analysis showed that four of the five tear products tested offered complete protection from desiccation (not different from naïve control), while one solution, which was hypotonic, offered partial protection (uptake different from desiccated and naïve corneas). The lens rewetting solution, which contains EDTA, did not protect the cornea from desiccation. This in vivo model is useful in evaluating artificial tear solutions for their ability to protect the corneal epithelium from damage during prolonged desiccating exposure. This method can be used to test toxicity of tear solution components, for preclinical evaluation of new tear formulas and may be useful for prediction of product efficacy in clinical use.