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.