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Abstract

We thank our colleagues for their interest in our study and for summarizing their previous excellent publications. After observing patient preference for aqueous chlorhexidine over povidone-iodine (PI) for many years, and considering the existing evidence, our ophthalmologists elected to use chlorhexidine exclusively for intravitreal injection antisepsis. Chlorhexidine has not been used widely in ophthalmology owing to concerns regarding toxicity, which stem from earlier case reports in which toxicity arose owing to the use of alcohol- or detergent-based formulations, rather than the aqueous form we describe.1Merani R. McPherson Z.E. Luckie A.P. et al.Aqueous chlorhexidine for intravitreal injection antisepsis: a case series and review of the literature.Ophthalmology. 2016; 123: 2588-2594Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar Shimada et al reserve chlorhexidine for patients with an “allergy” to PI. Modjtahedi et al have recently emphasized that true allergy to PI is very unlikely and most cases of intolerance are due to direct toxicity rather than true allergy.2Modjtahedi B.S. van Zyl T. Pandya H.K. et al.Endophthalmitis after intravitreal injections in patients with self-reported iodine allergy.Am J Ophthalmol. 2016; 170: 68-74Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar We highlighted that a longer contact time may be needed compared with PI, but scant ophthalmic data are available to support this. One of our ophthalmologists used a contact time of just 30 seconds and had no cases of endophthalmitis from 9266 injections in the present series.1Merani R. McPherson Z.E. Luckie A.P. et al.Aqueous chlorhexidine for intravitreal injection antisepsis: a case series and review of the literature.Ophthalmology. 2016; 123: 2588-2594Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar We also noted that the optimal concentration of aqueous chlorhexidine is not well-established. In our series, either 0.05% or 0.1% was used, but others have described using 0.2%. Toxicity has been reported with 0.5% chlorhexidine, but it is not known whether this toxicity relates to the higher concentration of chlorhexidine or the presence of cetrimide in that particular preparation.1Merani R. McPherson Z.E. Luckie A.P. et al.Aqueous chlorhexidine for intravitreal injection antisepsis: a case series and review of the literature.Ophthalmology. 2016; 123: 2588-2594Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar As summarized elsewhere, the optimal concentration for PI is also debatable.3Merani R. Hunyor A.P. Endophthalmitis following intravitreal anti-vascular endothelial growth factor (VEGF) injection: a comprehensive review.Int J Retina Vitreous. 2015; 1: 9Crossref PubMed Scopus (58) Google Scholar Although lower concentrations of PI liberate more free iodine,4Berkelman R.L. Holland B.W. Anderson R.L. Increased bactericidal activity of dilute preparations of povidone-iodine solutions.J Clin Microbiol. 1982; 15: 635-639Crossref PubMed Google Scholar there is a smaller reservoir of available free iodine that can be exhausted in the presence of a higher bacterial load.5Ferguson A.W. Scott J.A. McGavigan J. et al.Comparison of 5% povidone-iodine solution against 1% povidone-iodine solution in preoperative cataract surgery antisepsis: a prospective randomised double blind study.Br J Ophthalmol. 2003; 87: 163-167Crossref PubMed Scopus (116) Google Scholar It is for this reason that repeated application is needed if using very dilute concentrations of PI (e.g., 0.25%), but this may not be practical for procedures of very short duration such as intravitreal injections. There is no question that the evidence base for PI is much greater than for chlorhexidine in ophthalmology. Further validation is needed to establish the optimal concentration and contact time for chlorhexidine, and to determine the risk of allergy and resistance. Our series will hopefully serve as a springboard for such research. Although a randomized, controlled trial to compare PI and chlorhexidine would require a huge number of patients, such a comparison could be feasible if incorporated into other large, randomized, controlled trials. By publishing our experience we hope to have begun to challenge the misconception in ophthalmology that aqueous chlorhexidine is toxic, ineffective, or both. Re: Merani et al.: Aqueous chlorhexidine for intravitreal injection antisepsis (Ophthalmology. 2016;123:2588-2594)OphthalmologyVol. 124Issue 7PreviewWe read with interest the article by Merani et al1 on aqueous chlorhexidine for intravitreal injection antisepsis. Multidrug-resistant bacteria and Candida albicans are becoming more common as causative microorganisms of endophthalmitis; vancomycin-resistant bacteria have been reported. Because of the lack of effective antibiotics, endophthalmitis caused by multidrug-resistant bacteria tends to have a poor outcome. Thus, the use of povidone-iodine and chlorhexidine that have wide antimicrobial spectrum becomes more important. Full-Text PDF