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Clinician recommends dual treatment for corneal ulcers
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ATLANTA – “We may be moving out of the era of single-agent response to corneal ulcers,” Aaron Bronner, OD, said here in a presentation at SECO. “This treatment will fail more frequently because of resistance trends.”
He said fluoroquinolones are effective against gram-negative pathogens.
“The problem is that MRSA/MRSE are becoming more common,” Bronner said. “Staphylococcal species are the most common cause of corneal infection, and between 38% and 50% of these ulcers are either MRSA or MRSE, which have very low levels of susceptibility to even the new generations of fluoroquinolones such as moxifloxacin and gatifloxacin.”
Besivance (besifloxacin, Bausch + Lomb) has no systemic equivalent, he said, and was shown by the ocular ARMOR study to have the best efficacy of any fluoroquinolone against MRSA.
“The issue is that in clinical practice, I haven’t seen that Besivance performs any better than the fourth-generation fluoroquinolones when dealing with resistant bugs, and, because there is no systemic equivalent, most micro labs are unable to acquire MIC discs to test for sensitivity to besifloxacin” Bronner said. “If a culture result has identified a moxifloxacin-resistant bug, do you put your patient on besifloxacin? I don’t. That doesn't mean I don't use Besivance for corneal ulcers, but when I do, and I think I'm dealing with a gram-positive pathogen, I will always pair it with another agent effective against MRSE and MRSA, such as trimethoprim/polymyxin B or one of the aminoglycosides. I’ll use dual agents. While prescribing dual agents may seem unwieldy, it actually puts us back in line with what is traditionally done at the highest levels. Corneal clinics have done this for decades with dual broad-spectrum fortified agents.”
PACK-CXL, which is photoactivated chromophore with cross-linking, is being investigated for infectious keratitis.
“You put riboflavin on the eye, expose it to UV light, the riboflavin gets activated, and that creates free radicals, suppressing replication and making the cornea stiffer,” Bronner said. “It’s been studied anecdotally for all of the big groups of pathogens.”
He said it does not work against viral infections, “but seems to work for most etiologies of infectious keratitis, including bacterial, fungal and protozoan.
“The concept is good, but I don’t think it will disseminate rapidly because it falls more in line with front-line treatment and it’s experimental,” Bronner continued. “We have used this as a supplement to antimicrobials.”
Iodine is a “delightfully toxic element” that has developed no resistance despite being used as a tissue disinfectant for more than 100 years, he said.
“It’s effective against everything: gram positive, gram negative, fungus, protozoan,” he said.
A recent study showed that Betadine (povidone-iodine ophthalmic solution, Alcon) 1% had efficacy similar to ciprofloxacin and neomycin-polymyxin B-gramicidin in patients hospitalized for corneal ulcers in India and the Philippines.
“This frees us up to use it in the U.S., but we don’t use it a lot because it hurts,” Bronner said.
Amniotic membranes have well-established anti-inflammatory properties and are purported to be somewhat antimicrobial, Bronner said, but it should not be thought of as a supplement to the antimicrobial component of treatment.
“We do use Prokera (BioTissue) in healing chronic epithelial defects,” he said. “Amniotic membrane can help if re-epithelialization is slow to occur.”
Bronner discussed the role of steroids in treating corneal ulcers.
“Do not put steroids on corneal pathology unless you know what you’re dealing with,” he said. “If you use a steroid, at least make an attempt to sterilize the corneal ulcer before you add it.”
Community practice is split as far as using steroids for adjunctive therapy in Acanthamoeba keratitis, Bronner said.
“It promotes proliferation of organism, but also inhibits encystment of organism,” he said.
Consider steroids for Acanthamoeba only after effective anti-amoebic therapy has been used for several weeks and only on a case-by-case basis, Bronner added.
“If you’re not comfortable managing corneal ulcers, refer,” he said. – by Nancy Hemphill, ELS, FAAO
References:
Bronner A. An ulcer walks into your office ... Presented at: SECO; Feb. 28-March 4, 2017; Atlanta.
Isenberg SJ, et al. Am J Opthalmol. 2016;doi:10.1016/j.ajo.2016.10.004.
Disclosure: Bronner reported no relevant financial disclosures.