EyeWorld Asia-Pacific March 2019 Issue

62 March 2019 EWAP CORNEA How to treat corneal ulcers unresponsive to fluoroquinolones by Lauren Lipuma EyeWorld Contributing Writer Experts recommend identifying the infectious agent and modifying treatment C orneal ulcers are common but can be difficult for ophthalmologists to diagnose. It is not always easy to identify the underlying infection, and when the ulcer is unresponsive to the first line of treatment—a fluoroquinolone— physicians may be unsure what to do next. Cornea specialists addressed this issue during the “Cornea Essentials” symposium at the 2018 ASCRS•ASOA Annual Meeting. The purpose of the session was to run through common cornea scenarios and discuss some of the questions that come up when treating these patients, said Francis Mah, MD, Scripps Clinic Medical Group, La Jolla, California, who moderated the session. Brandon Ayres, MD, cornea service, Wills Eye Hospital, Philadelphia, described a two-pronged approach for treating corneal ulcers that are unresponsive to fluoroquinolones. First, identify the infectious agent, if possible; second, modify your treatment based on what you find. Ophthalmologists can’t always identify which kind of microbe is causing the infection, but culturing a sample of the cornea may offer some clues, according to Dr. Ayres. “There is no way you can look at a corneal ulcer and say, ‘I know what this is,’ because you will get tricked,” Dr. Ayres said. “But you can get a general sense of the infectious agent. It does help you steer what you’re going to do.” Identifying the infectious agent At the slit lamp, use topical anesthesia and a sterile spatula or calcium alginate swab to get a tissue sample from the cornea, Dr. Ayres said. Culture the sample in several types of culture medium, like blood, chocolate, Sabouraud, and thioglycollate. Use the cultures to perform multiple smears; do a Gram stain to see if the bacteria is Gram positive or negative, a calcofluor stain to see if it is fungal, and a hematoxylin and eosin stain to look for Acanthamoeba . “If you don’t have access to culture medium, it’s because you haven’t tried to get access to culture medium,” said John Berdahl, MD, Vance Thompson Vision, Sioux Falls, South Dakota. “Get a fridge, talk to your local hospital. It’s on you if you don’t have access to it.” Also look for clues in the patient’s history, like contact lens wear, exposure to vegetative matter, or swimming in lakes or rivers, Dr. Ayres said. Minimize steroid use until the infectious agent is identified and do a careful history and exam, looking for neurotropism and lid abnormality, he added. If you’re having trouble getting a tissue sample or culturing the organism, take the patient to the operating room (OR), pass a microsuture through the stroma and let it grow in thioglycollate broth, said Kenneth Beckman, MD, Comprehensive 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 unrevealing, 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, Virginia, 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 An ulcer caused by Streptococcus pneumoniae infection. Most corneal ulcers are bacterial and Gram positive. An ulceration caused by Pseudomonas bacteria that has spread to the sclera. Fungal keratitis present under LASIK flap. Keratitis caused by Acanthamoeba infection. Source: Brandon Ayres, MD Continued on page 64