Abstract
PURPOSE: Topical corneal local anesthetics are short acting and may impair corneal healing. In this study we compared corneal anesthesia and toxicity of topically applied N-ethyl lidocaine (QX-314) versus the conventional local anesthetic, proparacaine (PPC). METHODS: Various concentrations of QX-314 and 15 mM (0.5%) PPC were topically applied to rat corneas. Corneal anesthesia was assessed with a Cochet-Bonnet esthesiometer at predetermined time points. PC12 cells were exposed to the same solutions to assess cytotoxicity. Repeated topical corneal administration in rats was then used to assess for histologic evidence of toxicity. Finally, we created uniform corneal epithelial defects in rats and assessed the effect of repeated administration of these compounds on the defect healing rate. RESULTS: QX-314 (15 mM) and PPC (15 mM) caused similar total duration (114 ± 17 and 87 ± 16 minutes, respectively; P = 0.06) of anesthesia. The depth of anesthesia was similar between these low-dose groups at 15 minutes after application (1.8 ± 0.3- and 2.0 ± 0.8-cm filament lengths). QX-314 (100 mM) provided more prolonged corneal anesthesia (174 ± 13 minutes; P < 0.0001), with improved depth at 15 minutes (0.7 ± 0.3-cm filament length; P = 0.007). All tested concentrations of QX-314 demonstrated similar or less toxicity than 0.5% PPC. CONCLUSIONS: Topical administration of QX-314 is effective for corneal anesthesia and demonstrates no histologic signs of local toxicity in a rodent model. In higher concentrations, QX-314 provides more than twofold the duration of anesthetic effect than does 0.5% PPC. TRANSLATIONAL RELEVANCE: Our study reveals a clinically relevant compound providing prolonged duration topical corneal anesthesia.