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M. Nakamura, S.–I. Hirai, M. Kawahara, K. Sakamoto, A. Kimura; Analysis of Tear Film Stability With a Corneal Topographic Modeling System in Rabbits . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4437.
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Purpose: Corneal surface regularity, as reflected by the surface regularity index (SRI) determined with a corneal topographic modeling system, is abnormal in individuals with dry eye. This irregularity of the corneal surface is thought to be caused by changes in the tear film. Evaluation of corneal surface regularity thus represents a noninvasive, objective, and sensitive method for analysis of tear film stability. The aims of the present study were to establish a method for measurement of tear film stability in rabbits, to examine whether topographic irregularity causes corneal epithelial damage, and to investigate the effects of various topical lubricants on the SRI. Methods: The corneal SRI of anesthetized male Japanese white rabbits was measured with a corneal topographic modeling system at 0, 10, 20, 30, and 60 min after the instillation of 0.1% hyaluronan or saline into the eye. Corneal epithelial damage was evaluated after the last measurement of SRI by staining of the cornea with methylene blue. The SRI was also evaluated 0, 10, or 20 min after the instillation of 0.5% methylcellulose, 0.35% carboxymethylcellulose, or 1.0% chondroitin sulfate (CS). Results: Eyes instilled with saline manifested a time–dependent increase in the SRI of the cornea. Instillation of hyaluronan prevented the increase in SRI for up to 20 min. Methylene blue uptake into the cornea was significantly greater for eyes that received saline than for those treated with hyaluronan. Whereas eyes instilled with methylcellulose or carboxymethylcellulose manifested an increase in the SRI similar to that apparent in eyes that received saline, those treated with CS did not exhibit an increase in SRI for up to 10 min. Conclusions:A method was established for analysis of tear film stability in rabbits. This method revealed that tear film instability is related to corneal surface damage, and that topical instillation of 0.1% hyaluronan or 1.0% CS may prove effective for the treatment of dry eye.
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