Effect of artificial tears on cultured keratocytes in vitro

We investigated the effects of artificial tears on cultured rabbit and human keratocytes in vitro. The cells were exposed to seven nonpreserved commercially available artificial tear formulations and examined under phase- contrast microscopy for 60 min. After 5-min exposures to the solutions, rabbit keratocytes were fixed for transmission electron microscopy (TEM). In rabbit keratocytes, phase-contrast microscopy and TEM demonstrated that Aqua Site (CIBA Vision Ophthalmics, Atlanta, GA, U.S.A.), Hypo Tears PF (Johnson and Johnson, Claremont, CA, U.S.A.), and Tears Naturale Free (Alcon, Humacao, Puerto Rico, U.S.A.) immediately induced intracytoplasmic vacuoles and cell swelling, and subsequent cell degeneration. Rabbit cells exposed to the other artificial tears, which contained Ca²⁺ and did not contain EDTA, maintained their normal shape and appearance for 60 min. Phase-contrast microscopy of human keratocytes showed that Aqua Site and Hypo Tears PF induced mild and delayed cellular swelling, but the other artificial tears tested did not affect the cell shape for the entire 60-min observation period. Electrolyte balance and osmolarity of artificial tears appear to be critical for keratocyte survival. Maintenance of keratocyte integrity may be an important factor to consider when selecting an artificial tear preparation to be used when corneal epithelium is not intact.