Eyeworld

EW CORNEA 86 October 2018 Vancomycin is a good choice, if you have easy access to it, but consider trimethoprim if you don't, he said. Chloro-fluoroquinolones like besifloxacin are also a good op- tion. Besifloxacin has a lower mean inhibitory concentration than other antibiotics and has never been used systemically, so there is little chance of resistance, he said. It's important to remember that not all ulcers are the same; the treat- ment may depend on the ulcer's size and how much of an inflammatory reaction is present, according to Dr. Ayres. For smaller ulcers that are less than 2.5 millimeters in diameter, have a minimal anterior chamber reaction, and are not threatening the visual axis, culturing the tissue is a good idea but not essential, he said. Add a second antibiotic to kill any methicillin-resistant organisms, consider using besifloxacin, and continue using drops hourly until you see a clinical improvement, Dr. Ayres said. Be aware that the ulcer may progress for 24–48 hours even with appropriate management. Absolutely get a culture for large ulcers, where there is a deep, vision-threatening ulceration and a large inflammatory response, Dr. Ayres continued. But don't hold off on treatment if you can't culture the organism; change your treatment from a fluoroquinolone to fortified antibiotics hourly around the clock until you see an improvement, he said. EW Editors' note: Dr. Ayres has financial interests with Bausch + Lomb (Bridge- water, New Jersey). Dr. Beckman has no financial interests related to his comments. Dr. Berdahl has financial interests with Alcon (Fort Worth, Tex- as), Allergan, (Dublin, Ireland), and Bausch + Lomb. Dr. Mah has finan- cial interests with Allergan, Bausch + Lomb, and Novartis (Basel, Switzer- land). Dr. Yeu has financial interests with Johnson & Johnson Vision (Santa Ana, California). Contact information Ayres: bfast33@comcast.net Beckman: kenbeckman22@aol.com Berdahl: johnberdahl@gmail.com Mah: Mah.Francis@Scrippshealth.org Yeu: eyeulin@gmail.com If you're having trouble getting a tissue sample or culturing the organism, take the patient to the operating room (OR), pass a micro- suture through the stroma and let it grow in thioglycollate broth, said Kenneth Beckman, MD, Compre- hensive Eye Care of Central Ohio, Columbus. "You may not have access to cultures, but you do have access to an OR," Dr. Beckman said. "That's a good way to get a sample, even for someone who's been on drops." I typically reserve this for patients where the cultures were unreveal- ing, the ulcer is not responding, and the infection is deeper in the cornea. This allows me to access tissue within the actual infection. If this does not work, a corneal biopsy may be needed." Elizabeth Yeu, MD, Virginia Eye Consultants, Norfolk, Virgin- ia, recommended using confocal microscopy to look for hyphae to determine whether the infection is fungal. "Confocal microscopy in the setting of looking for hyphae is so helpful," Dr. Yeu said. "The hyphae are often abundant and clumped together, with a more classic appear- ance that looks like branching or unbranching bamboo. It is not un- common for the fungal smear to be negative, and the fungal culture can take 5–20 days for final results. I will initiate oral and topical anti-fun- gal therapy based on the confocal microscopy. Acanthamoeba can be more challenging to identify. The double-walled cysts of Acanthamoeba are often sparse and can be difficult to highlight among other debris and white cells within the infectious infiltrate." Treatment recommendations Once you have an idea of what the infectious agent is, you'll need to modify your treatment, according to Dr. Ayres. The majority of corneal ulcers are bacterial and Gram posi- tive; fungi and Acanthamoeba make up only a few percent of infections. If the fluoroquinolone anti- biotic is not working, adding a second agent may help. Penicillin derivatives may not be effective when treating Gram positive bac- teria, however, because methicillin resistance is growing among ocular pathogens and many organisms re- sistant to methicillin will be multi- drug resistant, Dr. Ayres said. How to continued from page 84 Stephens Instruments | 2500 Sandersville Rd | Lexington KY 40511 USA Toll Free ( USA ) 800.354.7848 | info@stephensinst.com | stephensinst.com © 2018 Stephens Instruments. All rights reserved. I N S T R U M E N T S | S I N G L E U S E | D R Y E Y E | B I O L O G I C S Take a closer look Stephens is more than instruments. 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