Corneal crosslinking (CXL) is a relatively safe and effective procedure to reduce or halt vision loss progression in keratoconic patients, but possible complications such as microbial keratitis do occur, which can lead to moderate to poor patient outcomes. When researchers in a study examined the clinical and microbiological features in patients who developed microbial keratitis post-CXL, they found the infection was predominately associated with gram-positive bacteria in most cases and delayed epithelialization in others.

The study looked at the medical records of 10 patients (11 eyes) who were operated on at the Sydney Eye Hospital between 2012-2019 and infected by microbial keratitis following CXL (median infection time post-surgery was four days but ranged from three to 83 among patients). For 42% of the patients, the causative organism was Coagulase-negative staphylococcus (CoNS). Although this is a healthy component of normal ocular flora, CXL may induce changes that prevent nonpathogenic floral bacteria from inhibiting pathogenic bacterial growth as it typically would. However, causative organisms are not the same in different parts of the world; for example, Fusarium spp rather than CoNS is the most common cause of microbial keratitis in India. For this reason, individual treatment must be determined based on pathogenic patterns.

“The causative organisms identified in case reports of post-CXL keratitis have ranged from bacteria to herpes virus, fungal and even Acanthamoeba,” the researchers wrote. “In our study, all causative organisms were bacteria, with S. aureus infection cases having worse patient outcomes. Two of the three cases required corneal transplantation” and a third’s vision declined to counting fingers. “These data from this study inform clinicians that early and prompt treatment is needed with patients identified with gram-positive organisms, such that postoperative antibiotic prophylaxis should include gram-positive cover.”

Topical steroids and bandage contact lenses are often recommended for patients following CXL, which could help with controlling inflammation and improving clinical outcomes. However, it is possible that steroids and contact lens use post-CXL could exacerbate an infection by exhibiting an immunosuppressive effect, causing bacteria to replicate. In this study, more than 70% of patients used topical steroids and wore a contact lens in the month prior to infection, and a previous study also found that delaying the use of topical steroids until the epithelium healed reduced the risk of infection. 

Remind your CXL patients to be extremely careful in the initial few weeks post-surgery to avoid touching and rubbing their eyes and applying eye drops without properly washing hands before. Stress the importance of postoperative treatment compliance and prioritizing hygiene to reduce the likelihood of infection.

Khoo P, Cabrera-Aguas M, Watson SL. Microbial keratitis after corneal collagen cross-linking for corneal ectasia. Asia-Pacific Academy of Ophthalmology. 2021. [Epub ahead of print].