Background: To evaluate the intraocular penetration of lidocaine 2% gel after different duration of application and to assess their effects on intraoperative pain.
Methods: Samples of aqueous humor were obtained in 41 eyes that had phacoemulsification under topical anesthesia with 2% lidocaine gel. The duration between lidocaine gel application and paracentesis was recorded. The aqueous concentration of lidocaine was measured using high performance liquid chromatography (HPLC). Patients were also asked to report the severity of intraoperative pain using a verbal analogue scale. Correlation analysis was performed to analyze the relationship between duration of lidocaine gel application, aqueous lidocaine concentration and intraoperative pain score.
Results: The mean duration of lidocaine gel application was 20.3+/-6.1 min and the mean aqueous lidocaine level was 14.2+/-8.5 micro g/ml. Longer duration of lidocaine gel application was significantly associated with higher aqueous concentration of lidocaine (Spearman's rho=0.58, P<0.001). Eyes in which lidocaine gel was applied for 20 minutes or more had significantly higher aqueous lidocaine level (two-tailed t-test, P=0.001) However, the duration of lidocaine gel application and the aqueous concentration of lidocaine showed no correlation with the patent's perceived pain score (P=0.20 and P=0.79, respectively).
Conclusions: Increase in duration of lidocaine gel application resulted in higher aqueous concentration of lidocaine. Patients' level of perceived pain during phacoemulsification under lidocaine gel anesthesia was not related to the intraocular lidocaine absorption level after 10 min of gel application.