Carbomer- Versus Cellulose-Based Artificial-Tear Formulations: Morphologic and Toxicologic Effects on a Corneal Cell Line

Frequent instillation of artificial tears is the primary disadvantage of the treatment for dry-eye syndrome. Recently gel formulations have been proposed as an alternative to classic cellulose formulations. The higher viscosity of these gels presumably prolongs tear-retention time in the eye and results in fewer daily applications. However, no toxicologic studies with gel formulations have been performed. Our aim was to study the toxic effects of these formulations on corneal cells. SIRC cells from rabbit cornea were exposed for 30 min, and 1, 3, and 6 h to five commercially available artificial tears, three of them carbomer gel formulations (Lacrivisc, Lacrivisc unit-doses, and Viscotears) and two carboxymethylcellulose (CMC) formulations (Celluvisc and Cellufresh). A cytotoxicity assay and a scanning electron microscopy (SEM) study were used to analyze the putative toxic effects of the formulations. The preservatives of the gel formulations also were tested. Carbomer gel formulations, both with and without preservatives, caused more in vitro toxic effects in the corneal cells than did CMC formulations and caused severe damage even after 30 min of exposure. SEM revealed dramatic cell-surface alterations. Preservatives added to Lacrivisc and Viscotears also had toxic effects on cells, whose effects were not significantly different from those of the commercial preparations. These results demonstrate that in the in vitro study, CMC artificial tears are less toxic than carbomer gel formulations. Questions about the benefits of using high-viscosity gels in the treatment of dry-eye syndrome still remain.