IN VITRO STUDY ON CORNEAL ENDOTHELIAL TOXICITY OF LIDOCAIN FOR INTRAOCULAR ANESTHESIA DURING CATARACT SURGERY
P. Eggeling, T. Heuermann, N. Anders, E. Bertelmann, P. Rieck
The intraocular use of lidocaine 1% as a local anesthetic for cataract surgery has recently been introduced into clinical practice. Although no side effects have been reported so far, studies on a possible toxic effect on the delicate corneal endothelium are currently not available.
Material and Methods: The endothelium of corneoscleral buttons excised of fresh pig eyes was exposed to different concentrations (1,5 and 10%) of unpreserved lidocaine over various time periods (1-60h) (n = 6 for each time and concentration). Control corneas were incubated with 0,9% NaCI respecting the same time points. Quantitation of endothelial damage was performed by means of the Janus green photometry technique. Light- and scanning electron microscopy were done to analyze morphological changes induced by lidocaine.
Results: Quantitative analysis of corneal damage in control corneas revealed a mean value of 6,5%. The contact of the endothelium to lidocaine did not significantly increase the rate of overall endothelial damage even with concentrations of 10% with all incubation times (mean value with 5% lidocaine; 7,8%). With 10% lidocaine, light microscopic evaluations revealed widened intercellular spaces but no other morphological changes.
Conclusion: Our results demonstrate a low toxicity of lidocaine on the corneal endothelium in vitro, even with higher doses than used for intraoculal injection. However, in view of the importance of the endothelium to corneal transparency, low concentrations of lidocaine should be used for intraocular anesthesia.
Supported by DFG Ri 568/3-1
Dpt. of Ophthalmology, Charité, Campus Virchow Klinikum, D-13353 Berlin