Eyeworld

60 | EYEWORLD | WINTER 2025 C ORNEA Contact Seitzman: Gerami.Seitzman@ucsf.edu Tuli: stuli@UFL.EDU Relevant disclosures Seitzman: None Tuli: None PhD, they've shown that metagenomic deep sequencing can reliably detect unexpected, fastidious, and atypical organisms in corneal samples. Dr. Tuli stressed that contacts lenses and contact lens hygiene are a big risk factor for many unusual corneal infections. Sleeping in, showering in, and swimming in contacts, not cleaning them, and buying them from non-tra- ditional sources are possible sources for an increased risk of all infections, but especially Acanthamoeba and fungus. Dr. Seitzman agreed that contact lens wear and water exposure are risk factors, particularly raising suspicion for Acanthamoeba. Any con- tact lens wearer diagnosed with HSV keratitis should be assumed to have Acanthamoeba first. "Post-surgical wounds, including LASIK flaps or corneal graft incisions, can harbor atypical mycobacteria," Dr. Seitzman said. "Agricultural trauma is a risk factor for fungal and nocardial infections, and of course, immunocompromised patients are more susceptible to atypical infec- tions in general." Treatment depends entirely on the organ- ism, Dr. Seitzman said. Acanthamoeba requires prolonged topical anti-amoebic therapy. Atypical mycobacterial infections often need combined topical and systemic antibiotics. In general, anti- microbial susceptibility testing is recommended to guide the treatment of atypical mycobacteria, she said. Triple therapy is commonly recom- mended. If susceptible, common topical treat- ments include amikacin, fluoroquinolones, and clarithromycin. Pythium can be very challenging to treat, Dr. Seitzman said. Topical linezolid and topical azithromycin are common first-line treatments with surgery commonly required for non-re- sponders. "Because these infections tend to present late and are more severe at diagno- sis, the treatment courses are longer and the outcomes less predictable compared to typical bacterial keratitis," she said. Dr. Seitzman reiterated that atypical in- fections often require long treatment courses. Acanthamoeba therapy, for example, has a mean treatment course of 4–6 months and even lon- ger in severe cases. Atypical mycobacteria also require extended therapy, with no well-defined clinical guidelines. "Treatment is individualized based on organism, sensitivities, and ocular surface comorbidities," she said. "Resolution is possible, but many patients are left with corneal scarring or need surgical intervention." Moving forward Dr. Tuli said that a new drug for Acanthamoeba has been approved in the E.U., PHMB 0.08%. She added that some studies have shown that crosslinking either with riboflavin with UV light or rose bengal with green light may help with Acanthamoeba and fungus, as well as atypical infections. Studies are still ongoing. Dr. Tuli stressed that having a high index of suspicion is important in cases that are not responding to treatment as expected or have unusual appearance. She also noted the impor- tance of culturing all larger or central ulcers, so that if there is an unusual organism it is picked up, and she recommended physicians become familiar with the ancillary treatment modalities, such as intrastromal injections. Dr. Seitzman is most excited about the ad- vances in diagnostics, particularly metagenomic deep sequencing, which allows for the detection of organisms without prespecifying a target. On the therapeutic side, there is ongoing interest in novel anti-amoebic agents and immunomodu- latory approaches, but most new strategies for atypical keratitis are still at the investigational stage. "The most important takeaway is that 'atypical' depends on your environment," Dr. Seitzman said. "Routinely culturing and keeping track of your local epidemiology is critical, and when you see an infection that worsens despite standard empiric therapy, always keep atypical organisms in mind." continued from page 59 Scedosporium apiospermum: an unusual filamentous fungal infection after a garden injury Source: Francis I. Proctor Foundation

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