Intracameral Antibiotics During Cataract Surgery: Barriers and Concerns
Although there is growing evidence to support the efficacy of intracameral antibiotic prophylaxis, the most important deterrent appears to be the lack of a commercially approved preparation in most countries, which explains the wide global variation in this practice. Using pharmacies to compound antibiotics raises the theoretical risk of introducing intraocular contaminants or adjuvants that can cause toxic anterior segment syndrome (TASS). Mixing antibiotics in the operating room raises the theoretical risk of dosing errors. Wong et al. reported transient macular edema in 6 of the 13 cases who received an overdose of intracameral cefuroxime. At least two cases of anaphylaxis associated with intracameral cefuroxime injection have been reported in the literature.[44,45]
Others have raised concerns that routine intraocular antibiotic prophylaxis can lead to increasing bacterial drug resistance.[46–48] A recent editorial by Naseri et al. effectively counters this concern by arguing that a one-time, highly concentrated dose of antibiotic injected into a physiologically isolated space is extremely unlikely to promote bacterial resistance. In fact, the concern over promoting antibiotic resistance should be directed more toward the common use of topical antibiotic prophylaxis.[39,50] PCR is one of the strongest risk factors for infectious endophthalmitis. Because of the evidence that intracameral moxifloxacin reduces the risk of endophthalmitis following PCR, surgeons not using routine intracameral antibiotic prophylaxis should strongly consider it in these higher risk eyes.
Endophthalmitis caused by cefuroxime-resistant organisms has been reported. Concerns have also been raised that intraocular moxifloxacin might not be effective for fluoroquinolone-resistant organisms. Although understandable, this theoretical concern may be misleading. After determining the MIC for endophthalmitis isolates in vitro, the characterization of antibiotic 'resistance' or 'sensitivity' is based on serum concentrations typically measured following systemic administration. However, analogous to intensive topical administration for corneal ulcers, direct intracameral injection achieves extremely high aqueous antibiotic levels that could never be attained systemically. Using postoperative aqueous taps, one study determined that the anterior chamber concentration of vancomycin exceeded the MIC for gram-positive organisms on average by a factor of 10 approximately 20 h after injecting 1 mg at the end of surgery. Because the efficacy of moxifloxacin is concentration dependent, we and others predict that the high intracameral levels from a direct injection would be effective against intraocular contamination with bacteria that might be 'resistant' to the much lower drug levels that would be achieved systemically. Libre postulates based on in-vitro studies that the 0.5 mg/0.1 ml intracameral moxifloxacin dose would be sufficient to eradicate resistant gram-positive organisms. This may explain the significant decrease in CoNS infections that we reported in our population following routine intracameral moxifloxacin prophylaxis.
Considering the rarity of endophthalmitis, the cost of routine intracameral antibiotic prophylaxis is another potential barrier and concern. However, a cost analysis in our 2016 AECS study found that the savings from treating 24 fewer endophthalmitis patients fully offset the additional costs of routine intracameral antibiotic prophylaxis in the 38 000 patients. Off label intracameral use of Vigamox in the United States without insurance coverage carries a high retail cost. However, common practice is to use the same bottle for topical prophylaxis resulting in no additional cost to patients using topical Vigamox. Although intracameral vancomycin was the most popular antibiotic chosen for intraocular prophylaxis in both the 2007 and 2014 ASCRS surveys, new evidence regarding its association with hemorrhagic occlusive retinal vasculitis (HORV) has led many surgeons to seek an alternative.[52–54,55] Published findings of a joint ASCRS–American Society of Retina Specialists (ASRS) task force on HORV included 36 eyes from 23 patients (13 bilateral cases). Every single case occurred following uncomplicated cataract surgery in which intraocular vancomycin was administered. HORV appears to be a type III hypersensitivity reaction to vancomycin, because the onset is delayed (mean onset after 1 week) and exposure of the second eye results in earlier and more severe vasculitis. Outcomes are frequently poor because of rapid onset of neovascular glaucoma. Although likely very rare, the true incidence of this devastating complication is unknown, and many surgeons have abandoned vancomycin for routine intracameral prophylaxis.
Curr Opin Ophthalmol. 2018;29(1):33-39. © 2018 Lippincott Williams & Wilkins