Effect of the use of artificial tears on the size of squamous cells of the rabbit corneal epithelium evaluated by scanning electron microscopy.

Optom Vis Sci 69(6):451-7 (1992) PMID 1641227

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.