Abstract
PurposeTopical 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).MethodsVarious 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.ResultsQX-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.ConclusionsTopical 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 RelevanceOur study reveals a clinically relevant compound providing prolonged duration topical corneal anesthesia.
Highlights
Cataract, and refractive surgeries are customarily performed without general anesthesia, ophthalmologists rely on topical or regional administration of amino-amide and amino-ester local anesthetics (LA) to facilitate painless surgery.[3,4]
Animals treated with 15 mM QX-314 had a similar strated 86.1% 6 10.5% viability compared with 1.1% 6 0.5% in cells treated with PPC 15 mM (P, 0.0001)
We studied the effect of QX-314 on corneal epithelial healing rates
Summary
The human cornea is densely innervated and exquisitely sensitive to noxious stimuli.[1,2] As corneal, cataract, and refractive surgeries are customarily performed without general anesthesia, ophthalmologists rely on topical or regional administration of amino-amide and amino-ester local anesthetics (LA) to facilitate painless surgery.[3,4] Single-dose administration of such agents is common in the acute care setting to facilitate fluorescein examination and irrigation of debris in the setting of corneal abrasions.[5,6] Shortcomings of available topical LA agents include a short duration of effect,[7] the potential for corneal toxicity,[7,8] and the retardation of corneal epithelial healing.[9,10] It is desirable to find alternative topical ophthalmic anesthetics with prolonged duration of effect and reduced local toxicity.N-ethyl-lidocaine (QX-314) is a lidocaine derivative with a quaternary amine moiety conferring an TVST j 2019 j Vol 8 j No 5 j Article 28.
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