Use of intravitreal chlorhexidine for sterilizing the vitreous cavity in bacterial endophthalmitis

Abstract

Purpose : To test the safety and efficacy of intravitreal chlorhexidine for sterilizing vitreal cavity in bacterial endophthalmitis.

Methods : Full-thickness retina explants were harvested from freshly enucleated (<24 hours) donor eyes. 6-mm patches of the retina were incubated in a CO₂-independent medium with varying concentrations (0.625-800 µg/ml) of chlorhexidine digluconate under air at 37°C within a humidified incubator for 24 hours. Retinal strips kept in the CO₂-independent medium served as controls. At the end of the incubation period, retinal cell viability was determined using an ethidium/calcein-based assay. To test the bactericidal effect of the studied chlorhexidine concentrations (0.625-800 µg/ml), quantitative suspension test method was employed on a Staphylococcus aureus strain. In vivo confirmation of the results was also carried out using albino rabbits. For this purpose, varying concentrations (50-400 µg/ml) of chlorhexidine digluconate were injected into rabbit eyes. Retinal toxicity was assessed by flash electroretinography (ERG) that was performed at 6 and 24 hours after the injection. Light microscopy was also employed to determine the effect of chlorhexidine on retinal structure. Fellow eyes that received the same volume of the solvent into the vitreous cavity served as the control.

Results : Concentrations of chlorhexidine below 200 µg/ml did not impair retinal cell viability for up to 24 hours in vitro, while concentrations above 6.25 µgr/ml exerted bactericidal effect. No evidence of toxicity was noted on the ERG and retinal histology at concentrations below 200 µgr/ml.

Conclusions : Intravitreal chlorhexidine exerts bactericidal effect at doses >6.25 µgr/ml. Intravitreal concentrations up to 200 µg/ml do not cause any noticeable retinal cytotoxicity for up to 24 hours. While high concentrations within this range can be used acutely to sterilize the globe in endophthalmitis without the concern of bacterial resistance, lower concentrations can be prophylactically used during intraocular surgeries or as a first aid in traumatic globe injuries.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.