Abstract
Purpose :
Variability in the preoperative preparation of the eye for cataract surgery exists with respect to the order in which surgeons apply lidocaine gel for anesthesia and povidone-iodine (PI) for antisepsis. Previous in vitro studies have demonstrated that lidocaine gel may act as a mechanical barrier and decrease the antimicrobial efficacy of PI. The aim of this study is to determine if these findings are replicable with in vitro and in vivo models, which would strengthen the evidence for the need to standardize the sequence of preoperative aseptic preparation.
Methods :
In vitro antibacterial effects were tested against Staphylococcus aureus (S. aureus) with disc diffusion methods for application of lidocaine gel alone, PI alone, PI before lidocaine gel, and lidocaine gel before PI. Lidocaine gel and/or PI in their respective sequences were applied to a circular piece of hole-punched filter paper before being placed on a plate. All plates were incubated at 37°C overnight and bacterial zones of inhibition were estimated. In vivo studies were then performed using C57BL/6 mice. Mouse eyes were colonized with S. aureus to which lidocaine gel alone, PI alone, PI before lidocaine gel, lidocaine gel before PI, and S. aureus alone were applied. The eyes were then rinsed with saline, and the runoff fluid was collected, diluted, and plated on agar for viable bacterial estimation after incubation overnight at 37°C.
Results :
In vitro studies demonstrated a significantly smaller (P<0.001) mean zone of inhibition when lidocaine was applied before PI versus PI alone. Zones of inhibition were not significantly different between PI alone versus PI applied before lidocaine and PI applied before lidocaine versus lidocaine applied before PI (P>0.05). In vivo studies showed that mouse eyes treated with lidocaine prior to PI had significantly more S. aureus growth compared to eyes that had PI applied prior to lidocaine (P<0.001).
Conclusions :
Both in vitro and in vivo studies demonstrated that lidocaine gel interfered with PI’s antiseptic properties when placed between the surface and PI. Our results are consistent with previous in vitro studies and provide greater evidence for applying PI before lidocaine gel if a viscous anesthetic agent is used to ensure optimal antisepsis is achieved.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.