PURPOSE: To quantify the mydriatic effect and side effects of topical lidocaine hydrochloride with different pH values and concentrations in healthy volunteers. SETTING:Umeå University Hospital Eye Clinic, Umeå, Sweden. METHODS: In this intraindividual comparison double-masked randomized study, healthy volunteers were given topical lidocaine 8%, lidocaine 8% pH 6.0, or a placebo 3 times at 90-second intervals. Thereafter, a drop of tropicamide 0.5% or placebo was given (tropicamide setting). Another group of healthy volunteers was given topical lidocaine 4%, 8%, or 16% 3 or 6 times at 90-second intervals (dose-response setting). Before and 15, 30, 60, and 180 minutes after eyedrop instillation, the near point was determined and Scheimpflug photography was performed. RESULTS: The tropicamide setting comprised 26 volunteers (mean age 23.5 years) and the dose-response setting, 10 volunteers (mean age 24.5 years). The direct mydriatic effect of lidocaine was larger at pH 6.0 (mean peak effect 0.61+/-0.06 [SEM] versus 0.42+/-0.04 mm) (P< .05), and the augmentation of tropicamide mydriasis was larger at pH 6.0. Lidocaine 8% had a better direct mydriatic effect than lidocaine 4% and lidocaine 16% (mean peak effect 0.60+/-0.09 mm versus 0.19+/-0.08 mm and 0.28+/-0.10 mm, respectively) (P< .01). Lidocaine 16% given 6 times caused corneal side effects. CONCLUSIONS:Lidocaine 8% with pH 6.0 had a maximum direct mydriatic effect and gave maximum augmentation of tropicamide mydriasis without causing unwanted corneal side effects and thus should be preferable for topical anesthesia in cataract surgery.
RCT Entities:
PURPOSE: To quantify the mydriatic effect and side effects of topical lidocaine hydrochloride with different pH values and concentrations in healthy volunteers. SETTING: Umeå University Hospital Eye Clinic, Umeå, Sweden. METHODS: In this intraindividual comparison double-masked randomized study, healthy volunteers were given topical lidocaine 8%, lidocaine 8% pH 6.0, or a placebo 3 times at 90-second intervals. Thereafter, a drop of tropicamide 0.5% or placebo was given (tropicamide setting). Another group of healthy volunteers was given topical lidocaine 4%, 8%, or 16% 3 or 6 times at 90-second intervals (dose-response setting). Before and 15, 30, 60, and 180 minutes after eyedrop instillation, the near point was determined and Scheimpflug photography was performed. RESULTS: The tropicamide setting comprised 26 volunteers (mean age 23.5 years) and the dose-response setting, 10 volunteers (mean age 24.5 years). The direct mydriatic effect of lidocaine was larger at pH 6.0 (mean peak effect 0.61+/-0.06 [SEM] versus 0.42+/-0.04 mm) (P< .05), and the augmentation of tropicamidemydriasis was larger at pH 6.0. Lidocaine 8% had a better direct mydriatic effect than lidocaine 4% and lidocaine 16% (mean peak effect 0.60+/-0.09 mm versus 0.19+/-0.08 mm and 0.28+/-0.10 mm, respectively) (P< .01). Lidocaine 16% given 6 times caused corneal side effects. CONCLUSIONS:Lidocaine 8% with pH 6.0 had a maximum direct mydriatic effect and gave maximum augmentation of tropicamidemydriasis without causing unwanted corneal side effects and thus should be preferable for topical anesthesia in cataract surgery.