Effect of the use of artificial tears on the size of squamous cells of the rabbit corneal epithelium evaluated by scanning electron microscopy.
Female pigmented rabbits (2 to 2.3 kg) received 2 drops of a chlorobutanol 0.5%-preserved, polyvinyl alcohol-based artificial tear at 21.00 h and 09.00 h for 1, 2, 3, 6, or 12 days. The animals were euthanized at 15.00 h and the corneas fixed with 2.0% glutaraldehyde in 80 mM cacodylate buffer. Scanning electron micrographs were taken close to the corneal center at 500 x magnification and normal to the epithelial surface. The surface areas of the squamous cells were measured with a digitizer pad. As a result of the treatment, up to 9% of the cells were observed to be in the process of exfoliation with the effect being greatest after 3 days. Control (nontreated) corneas showed only 0.44% exfoliating cells. Over this time period there was a progressive shift of cell sizes to larger values followed by recovery back to control values by 12 days. The results confirm the lack of gross cytotoxic effect of chlorobutanol-preserved artificial tears and indicate that the corneal epithelium can adapt to the use of a polymer-containing artificial tear.
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