[Diffusion if lidocaine after intracameral injection]

To determine the lidocaine diffusion space, we compared lidocaine aquous humor concentration in topical anesthesia with 1% lidocaine intracameral injection and in peribulbar anesthesia with 2% lidocaine prior phacoemulsification.

A gas chromatography technique of analyzing 100 microliters aqueous humor was used to detect the presence of lidocaine prior to phakoemulsification cataract surgery in two groups of patients: group A: after peribulbar anesthesia with 10 ml 2% lidocaine, group B: after 1% tetracaine topical anesthesia and 0.5 ml intracameral injection of 1% preservative-free lidocaine. The intracameral volume was estimated mathematically in group B. Endothelial cells loss was analyzed in two groups with non contact specular microscopy.

Lidocaine was detected in aqueous humor with a good reliability. The mean concentration after intracameral injection was 6,300 micrograms/ml and was higher than after peribulbar injection. This concentration was near than theorical intracameral rate, suggesting that there was no diffusion in the posterior segment. There was no significant difference in the 2 groups in endothelial cells loss.

Intracameral injection of lidocaine is an effective technique to anesthetize intracameral structures without diffusion in posterior segment prior to phakoemulsification.