[Diffusion if lidocaine after intracameral injection]

Area of Science:

• Ophthalmology
• Anesthesia
• Pharmacokinetics

Background:

• Cataract surgery requires effective anesthesia for intraocular structures.
• Understanding local anesthetic diffusion is crucial for surgical safety and efficacy.
• Previous methods like peribulbar anesthesia raise concerns about potential posterior segment spread.

Purpose of the Study:

• To compare the diffusion of lidocaine in aqueous humor following intracameral injection versus peribulbar anesthesia.
• To quantify lidocaine concentration in the anterior chamber after different anesthetic techniques prior to phacoemulsification.
• To assess the safety of intracameral lidocaine regarding corneal endothelial cell loss.

Main Methods:

• Two groups of patients undergoing phacoemulsification were studied.
• Group A received peribulbar anesthesia with 2% lidocaine; Group B received topical tetracaine with intracameral 1% lidocaine.
• Aqueous humor lidocaine concentration was measured using gas chromatography; endothelial cell loss was assessed via specular microscopy.

Main Results:

• Lidocaine was reliably detected in the aqueous humor.
• Mean intracameral lidocaine concentration (6,300 µg/ml) was significantly higher than with peribulbar anesthesia.
• No significant difference in endothelial cell loss was observed between the groups, and intracameral levels suggested limited posterior diffusion.

Conclusions:

• Intracameral lidocaine injection is an effective method for anesthetizing intraocular structures during cataract surgery.
• This technique achieves high concentrations in the anterior chamber with minimal diffusion into the posterior segment.
• Intracameral lidocaine offers a safe and effective anesthetic option for phacoemulsification, preserving corneal endothelial cells.