AbstractMost ophthalmic preparations contain preservatives. Some are toxic to healthy corneal epithelium or retard healing of corneas from which part or all of the epithelium has been removed leaving an intact basement membrane. In this paper, the effect of commonly used concentrations of benzalkonium chloride (BAC), thimerosal, and ethylenediaminetetracetic acid (EDTA) upon the healing of rabbit corneas after partial lamellar keratectomy is investigated. This model has not been used previously for a study of preservative toxicity. Thimerosal (0.004%), BAC (0.01 %), or EDTA (0.1%) applied four times per day had no significant effect on the corneal healing or epithelial migration rates. A slight retardation occurred when BAC (0.01%) and EDTA (0.1%) were used together, while healing failed to occur as long as benzalkonium chloride (0.02%) was administered.