EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78716
February 2011 March 2012 EW REFRACTIVE Handling atypical microbial keratitis after laser refractive surgery by Maxine Lipner Senior EyeWorld Contributing Editor How these unusual organisms are confounding practitioners A typical microbial keratitis after refractive surgery is thankfully a rare event. It affects just 0.035% of post-LASIK cases and about 0.2% of instances following photorefractive keratectomy, accord- ing to Daya P. Sharma, M.D., refrac- tive surgery fellow, Emmetropia Mediterranean Eye Clinic, Crete, Greece. In an article that appeared in the July 2011 issue of Future Microbiology, investigators led by Dr. Sharma reviewed what happened in instances involving atypical micro- bial keratitis cases. Dr. Sharma was moved in part to undertake the literature review by three cases of atypical infection that he saw after LASIK. "But the main motivation for the study was to review an important condition that happens infrequently but could cause a potentially serious problem after refractive surgery," Dr. Sharma said. "So it's important for any re- fractive surgeon to know about it." He pointed out that if not picked up and managed early, particularly fun- gal keratitis after LASIK can cause devastating results. Shifting atypical landscape One of the pivotal findings here came from a study published in the July 2011 issue of the Journal of Cataract & Refractive Surgery, which highlighted a 2008 ASCRS survey. "The key finding was that the proportion of organisms that are causing infection after LASIK is changing; the incidence of MRSA— methicillin-resistant Staphylococcus aureus—is increasing and the inci- dence of atypical mycobacteria is de- creasing," Dr. Sharma said. He sees that as likely the result of changing from microkeratome LASIK to fem- tosecond LASIK. "We know that the sterilization process for the micro- keratome head can increase the risk of atypical mycobacteria being pres- ent in the operating theater environ- ment," Dr. Sharma said. "Atypical mycobacteria can also occur after femtosecond LASIK and after LASIK retreatment, so changing to fem- tosecond LASIK doesn't exclude the possibility, but it seems to reduce the risk of atypical mycobacteria." diagnosed, the flap should be lifted and cultures should be done, unless there's an easily assessable infiltrate from an epithelial defect, so that a specific diagnosis can be made and antibiotic sensitivities can be deter- mined," Dr. Sharma said. Although atypical infections A recent study found that the incidence of MRSA keratitis after LASIK (pictured here) is increasing and the incidence of atypical mycobacteria is decreasing Source: Eric D. Donnenfeld, M.D. The study was also revealing of the types of organisms that can occur. "Some of them are quite rare and wouldn't be expected to be seen that commonly," Dr. Sharma said. "So it's important to keep in mind that there are other potentially seri- ous organisms that can occur." Diagnostic dilemmas Diagnostics can be a vexing issue when it comes to atypical cases. While confocal microscopy can be useful in some cases, this can steal valuable time in others. "Although that's a useful diagnostic method, sending a patient for confocal mi- croscopy could delay the diagnosis," Dr. Sharma said. "You may be better off taking the patient to the operat- ing theater, lifting the flap, and tak- ing specific microbiological studies." He pointed out that it is very impor- tant to make an early diagnosis and be suspicious of more serious infec- tions such as fungal keratitis. Dr. Sharma pointed to poly- merase chain reaction (PCR) as a po- tentially valuable diagnostic tool here. "I personally think that it's something that should be utilized more, and the reason for that is that it's something that can be done on samples that are taken at any cen- ter," Dr. Sharma said. "If you have an operating room microscope you can take samples through your slides, the cultures, and you can send these samples for PCR." One of the main problems that Dr. Sharma finds with unusual or- ganisms such as Acanthamoeba or fungal keratitis is that culturing methods can take quite a long time. "It can take up to 2 weeks to get a culture back if there is a culture re- sult," Dr. Sharma said. "So it can re- sult in significant delays." By contrast, the PCR test is rapid. "The test itself is hours rather than days to weeks," Dr. Sharma said. Of course logistics can come into play and depending upon where the lab is and what the transportation to it is like, there can be some delays here as well. As far as treatment for these atypical cases, investigators found that the specifics in terms of drugs varied depending upon the region. However, some important rules of thumb emerged. "If the infection is Enhancement continued from page 104 Pearls differ Surgeons have different tips for maximizing retreatment surgery outcomes. For Dr. Talley-Rostov, one of the keys is waiting at least 3 months post-op for the cornea to "settle down." "I don't rush into an enhance- ment," she said. For retreatments of eyes with low amounts of stigmatism—up to about 1 D—Dr. Culbertson has begun using a femtosecond laser in the stroma or sub-Bowman's level for an arcuate keratotomy that does not break the incision through to the surface. EW Editors' note: Drs. Culbertson, Nichamin, Rapuano, Steinert, and Talley-Rostov have no financial interests related to this article. Dr. Trattler has financial interests with Abbott Medical Optics (Santa Ana, Calif.). Contact information Culbertson: 305-326-6364, wculbertson@med.miami.edu Nichamin: 814-849-8344, nichamin@laureleye.com Rapuano: 215-928-3180, cjrapuano@willseye.org Steinert: 949-824-8089, steinert@uci.edu Talley-Rostov: atalley-rostov@nweyes.com Trattler: 305-598-2020, wtrattler@gmail.com tend to be rare, if these are not picked up early enough, patients are inclined to do badly. With that in mind, Dr. Sharma urged practition- ers to be vigilant. "We should have a high index of suspicion for micro- bial keratitis," he said. "It should be managed aggressively including tak- ing the patient back and lifting the flap to obtain specific microbiologi- cal investigations." Going forward, one potential thing to consider for the treatment of these atypical infections may be crosslinking with application of ri- boflavin and UVA. "We have noted from other studies that riboflavin and UVA do have the potential to kill all sorts of organisms—bacteria, fungi, and even Acanthamoeba can be killed by this," Dr. Sharma said. "So potentially a large number of or- ganisms are sensitive to that sort of treatment." He pointed out that this is already undergoing clinical study for the treatment of microbial kerati- tis, and that some case reports have shown this to be successful in in- stances of infectious keratitis. EW Editors' note: Dr. Sharma has no financial interests related to this article. Contact information Sharma: dr.daya.sharma@gmail.com 105