Microbial Keratitis Following CXL Affects Patient Outcomes

Microbial keratitis following corneal collagen crosslinking (CXL) may result in moderate to poor patient outcomes, according to research results published in the Asia-Pacific Journal of Ophthalmology. 

Through a retrospective case series study, investigators reported on both clinical and microbial features of patients with microbial keratitis after CXL, in the largest cohort of these patients to date, according to the research team. 

Adult patients who presented to the Sydney Eye Hospital with microbial keratitis, a CXL history, and a corneal scrape performed between 2012 and 2019 were included in the study. Medical records were reviewed for sociodemographic information, ocular and systemic history, clinical presentation, pathology, management, and outcomes. 

In the 8-year study period, 10 eyes of 10 patients (2 women; mean age, 29±11 years) developed microbial keratitis after CXL surgery, with 1 patient reporting 2 episodes during the study period. Microbial keratitis incidence was 2.4%, or 6 of 246 patients.

The majority of patients (80%) underwent CXL procedures for keratoconus. The median time to infection after surgery was 4 days (interquartile range [IQR], 16-48). Median hospital admission was 9 days (IQR, 7.5-16) and median healing time was 30 days (IQR, 15-53).

At presentation, patients had a median visual acuity of 1.30 logMAR; final visual acuity was 0.83, representing a change of 0.4 logMAR from initial to final measurement. 

After CXL surgery, 81% of patients received topical fluoroquinolone and topical steroids. Most patients with microbial keratitis were treated using fortified antibiotics — 82% received a combination of gentamicin and cephalothin — with a modified treatment in 73% of patients. Moxifloxacin was the most commonly prescribed antibiotic. 

All patients ceased postoperative topical steroid therapy treatment at the initial microbial keratitis visit; this treatment was reintroduced in 82% of patients after the causative organism was identified. After corneal scrape, the median duration of topical steroid was 4 days (IQR, 3-7) with unpreserved prednisolone prescribed to 75% of patients. 

Eleven cases had predisposing risk factors to microbial keratitis, including bandage contact lens wear (82%) and topical steroid use (73%). Additional likely risk factors include corneal hydrops (9%), eczema (9%), previous refractive surgery (9%), and previous bacterial keratitis (18%). 

Eleven total corneal scrapes were performed, with 1 repeat scrape. Positive cultures were identified in 11 of 12 scrapes, with 13 isolates including Coagulase-negative Staphylococcus and Staphylococcus aureus. In the patient who required a re-scrape, Staphylococcus capitis and Pseudomonas synxantha were identified. 

At the final follow-up, 45% of eyes experienced a moderate outcome, including visual acuity between 6/12 and 6/60, while 55% had a poor outcome (visual acuity worse than 6/60). Two patients required corneal transplantation, 1 required penetrating keratoplasty, and 1 required deep anterior lamellar keratoplasty. 

Study limitations include those inherent to retrospective research and the potential overrepresentation of severe cases of microbial keratitis. 

“We recommend clinicians stress the importance to their patients to avoid touching and rubbing their eyes, washing their hands before instilling eye drops, and promote postoperative treatment compliance to avoid infections,” researchers report.  

Reference

Khoo P, Cabrera-Aguas M, Watson SL. Microbial keratitis after corneal collagen cross-linking for corneal ectasia. Asia Pac J Ophthalmol. 2021;10(4):355-359. doi:10.1097/APO.000000000000379