Povidone-iodine is still a premium antiseptic measure in ocular surgery.

Abstract

We would like to thank Oakley and Vote for sharing their experience and rationale in switching to aqueous chlorhexidine gluconate for antimicrobial prophylaxis during intravitreal injections (IVI) (Oakley & Vote 2016). There is no debating that strict aseptic technique and effective antisepsis are of utmost importance in prevention of endophthalmitis associated with any ophthalmic procedure. While chlorhexidine seems like a promising alternative to povidone-iodine (PVI) preparation, it is our view that at present there is no compelling reason warranting a change from current practice. Povidone-iodine (PVI) solutions in ocular site disinfection have been studied in projects focusing on large-scale epidemiological outcomes (Dossarps et al. 2015) as well as studies focusing on actual reduction of conjunctival flora (Apt et al. 1984). While the perfect PVI concentration may be a matter of debate and target for future studies, its effectiveness as an antiseptic as well as safety profile has been extensively tested. It is cheap and effective, and there have been no reports of resistance to PVI and no reports of anaphylaxis in topical ophthalmic use (Wykoff et al. 2011). Additionally, PVI does not seem to induce resistance or cross-resistance to antibiotics (Hsu et al. 2014). While chlorhexidine appears to be a promising alternative to PVI, especially for patients intolerant of the latter, there are a few caveats to adopting it for widespread use. Firstly, development of resistance to chlorhexidine has been demonstrated in vitro (Kunisada et al. 1997). Whether this effect persists in vivo in ocular flora is not known. Secondly, there have been reports of reduced susceptibility to chlorhexidine in methicillin-resistant Staphylococcus aureus, as compared to methicillin-susceptible S. aureus (Horner et al. 2012). Furthermore, specific, efflux-based, resistance mechanisms and genes coding for those to chlorhexidine have been identified in coagulase-negative staphylococci, including S. aureus (Horner et al. 2012). There was at least one reported epidemic related to contaminated chlorhexidine (Vigeant et al. 1998). Lastly, reduced effectiveness of chlorhexidine against fungi is of concern (Lachapelle et al. 2013). As to the referenced study by Trost et al. (2007) it is important to note that the authors used 0.1–0.4% PVI solution as an intravitreal injection, not topically. The study shows that small amounts of PVI injected intravitreally seem to have no observable toxic effect on ocular tissues in a rabbit model (Trost et al. 2007). This serves as reassurance that should a small amount of PVI be inadvertently transported into the anterior chamber during injection, it should not cause adverse effects for the patient. We applaud the effort authors went through to reduce patient-perceived pain during IVI. While studies regarding postinjection pain scores are few and far between, we have found two suggestions for minimizing postinjection pain. Merani & Hunyor (2015) suggest using lubricant preservative-free eyedrops one day before the injection to reduce pain levels. The use of 30-gauge needles has been reported to reduce pain scores in another study (Güler et al. 2015). Finally, lower concentrations of PVI provide another interesting alternative that may reduce pain associated with IVI. Povidone-iodine solutions as dilute as 0.1% were shown to have good in vitro activity (Berkelman et al. 1982) and continue to be effective in preventing endophthalmitis in vivo, with Shimada et al. (2013) reporting 0/15144 endophthalmitis rate after IVI with pre- and postprocedure, 5 ml 0.25% PVI flush.