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B.E. McCarey, F.E. Kane, K.E. Green; In vivo Corneal Deturgescence With a New Lubricant Eye Drop . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2992.
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Post–refractive patients can have immediate transient corneal edema. The denuded epithelial stroma of the post–PRK patient has the potential of significant edema. Clarity (Alimera) a new lubricant eye drop/dehydration solution is compared to Refresh Tears (Allergan) for corneal hydration control.
NZW rabbits (n=38 eyes) corneal/sclera rims were mounted in the laboratory perfusion specular microscope and the endothelial surface maintained with BSSplus (Alcon Lab). A series of experiments were performed with and without epithelium while the anterior corneal surface was bathed in Clarity or Refresh (full or 25% concentration to mimic tear dilution). Epithelial denuded corneas were swollen to 550µm before covering the stroma with the test solutions. Another experimental series with damaged epithelial cells was established with a 20 minute exposure to 0.01% BAK followed by a 60 minute bath in BSSplus. Epithelial and corneal thicknesses were recorded.
Swollen corneas without epithelium thinned 39% in 30 minutes with Clarity and 12% in 30 minutes with Refresh. Clarity at 25% strength demonstrated deturgescence for 50 minutes with 13% thinning, whereas Refresh at 25% strength demonstrated deturgescence for 50 minutes with 2% thinning. Intact corneas exposed to Clarity and Refresh had 9.6% and 8.5% thickness increases respectively and no change in epithelial thickness. When the test solutions were diluted to 25% concentration, no changes in either epithelial or corneal thicknesses were recorded. The BAK damage caused a corneal thickness increase of approximately 16.5% and an epithelial thickness increase of approximately 69%. Bathing the epithelium in 25% Clarity caused a 35% decrease in thickness at 40 minutes and 25% Refresh caused a respective 5% decrease.
The dehydration efficacy of tear lubricating solutions has been evaluated with an in vitro model. Clarity demonstrated a greater deturgescence than Refresh Tears at full and 25% concentrations in the denuded epithelial model. There was no significant difference in thickness changes in the intact epithelial model. The BAK damaged model showed a significantly greater thinning in the epithelium with Clarity than Refresh.
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