Background To investigate the biochemical changes on the oxidant/antioxidant balance in corneal and lens tissues in rabbits, and to determine the relative corneal endothelial toxicities following the injection of intracameral anaesthetic agents: levobupivacaine 0.5% or lidocaine 2%.

Methods The experiment was conducted using New Zealand rabbits. The rabbits were randomly divided into three experimental groups. Twenty eyes received injections of 0.2 ml of one of the two anaesthetic preparations and 10 control eyes received injections of 0.2 ml balanced salt solution. Corneal thickness and clarity were measured before and 3 and 6 h after surgery. Anterior chamber reaction was evaluated 1, 3 and 6 h after surgery. In corneal and lens tissues, malondialdehyde and total thiol levels were measured using spectrophotometric methods.

Results Levobupivacaine 0.5% caused corneal thickening, oedema and anterior chamber reaction (p<0.001). There were no biochemical changes in the levobupivacaine group (p>0.05). No change was observed in the corneal thickness, oedema and anterior chamber reactions, whereas the level of malondialdehyde significantly increased in corneal and lens tissues (p<0.001, p=0.015, respectively), and the level of total thiol significantly decreased in the lens tissue in the lidocaine 2% group (p<0.001).

Conclusions The results of this study suggest that levobupivacaine 0.5% has an immediate toxicity on corneal endothelium. Lidocaine 2% causes oxidative damage on corneal and lens tissues. Surgeons should not use repetitive and high doses of intracameral lidocaine in the presence of corneal pathology during cataract surgery.