Effect of tear lubricating solutions on in vivo corneal epithelial permeability

Abstract

PURPOSE. The rabbit corneal epithelial permeability was measured noninvasively following exposure to commercially available tear lubricating solutions. METHODS. The normal unanesthetized rabbit's corneal surface was either bathed in the tear lubricating solution for 5 min or received multiple applications of 2 drops per 30 min for 6 h for one or five days. The corneal epithelial permeability to carboxy-fluorescein after a 5-min bath was measured with the Fluorotron Master. Fifteen commercially available tear preparations were tested. RESULTS. The baseline corneal epithelial permeability was 0.0455 ± 0.0114 nm/s. The epithelial permeability values for the corneas bathed for 5 min in control solution (BSSplus) was 0.0798 ± 0.0074 nm/s, in the preservative-free tear lubricating solutions the range was 0.512 to 0.542 nm/s, and in the preserved tear lubricating solutions the range was 0.3518 to 11.8873 nm/s. The preservative-free tear lubricating solutions had epithelial cell permeabilities up to 6 times greater than the control solution. Whereas, the preserved tear lubricating solutions had epithelial cell permeabilities up to 149 times greater than the control solution. Multiple applications of the tear lubricating solutions for 5 days were less damaging to the epithelial permeability than the 5 min bath applications. The resulting epithelial permeabilities were up to 2 fold greater than the control with the corresponding preservative-free solution and up to 29 fold greater than control with the corresponding preserved solution. CONCLUSION. An extended exposure of 5 min to various tear lubricating solutions demonstrated significant differences in epithelial cell permeability between preserved solutions and unpreserved solutions, whereas the multiple drop application technique demonstrated all of the preservative-free solutions and some of the preserved solutions to be insignificantly different from the control solution.