Toxicity of topical anesthetic agents to human keratocytes in vivo

Purpose: To test the potential toxicity on human keratocytes of topical anesthetic agents used after photorefractive keratectomy (PRK) to reduce or eliminate pain. Setting: Department of Ophthalmology, Doheny Eye institute, University of Southern California. Los Angeles. California, USA. Methods: Cultured human keratocytes were incubated with commercially available tetracaine and proparacaine at reduced concentrations of 0.001%, 0.01%, 0.1%, and 0.25%. Evaluations were performed by phase-contrast microscopy and tetrazolium salt colorimetric assay every 2 hours for 12 hours after adding 1 of the anesthetic agents to the media. Results: After time of incubation and concentration were adjusted, both drugs reduced overall cell viability; however, tetracaine produced a larger decrease in cell viability than proparacaine (P = .008). For both drugs, significant differences were found among concentrations for and across time (P < .001 and P = .004, respectively). Conclusion: Both tetracaine and proparacaine had toxic effects on stromal keratocytes related not only to drug concentrations but also to time exposure. These findings; underscore the widespread concern that anesthetic drugs may affect corneal stromal wound healing after PRK. J Cataract Refract Surg 1999; 25:975-980 (C) 1999 ASCRS and ESCRS.