Do different osmolar solutions change the epithelial surface of the healthy rabbit cornea?

Background: We evaluated various osmolar solutions in use for ophthalmic treatment for their effect on the corneal surface. Healthy corneas were exposed to hypoosmolar balanced salt solution (BSS), an isoosmolar solution and hyperosmolar solution Previn.

Methods: Rinsing solutions--BSS from Opsia, and Previn from Prevor--were provided by the manufacturers. Our laboratory made an iso-corneal solution from an electrolytes and amino acid composition, based on our measurements for osmolarity of human corneas. During final anesthesia, each six healthy rabbit eyes were exposed to 1 drop of the above-mentioned solutions, every second for 120 min. Drops were applied from a height of 2 cm, wetting the corneal surface homogeneously.

Results: Surface changes compared to healthy corneas were visible in scanning-electron-microscope images. In grading such changes,we found that balanced salt solution caused changes within the surface appearance, with increased cell-shape changes and microvilli loss. Isoosmolar and Previn solution did not show slightly pronounced nuclei within an intact cellular membrane.

Conclusion: Isoosmolar and hyperosmolar rising did not change the microvilli of the corneal-cell surface. Hypoosmolar rinsing changed the surfaces considerably. We believe that, contrary to prevalent opinion, application of hyperosmolar solutions to the healthy eye does not harm corneal surface integrity. Iso-corneal solution and Previn solution did not change the surface of the healthy rabbit cornea.