Keratitis after keratoplasty: risk modifiers, microbial resistance and outcomes in the COVID-19 era

This study evaluated the risk of keratitis following corneal transplantation in Auckland, New Zealand, a mild, humid, subtropical climate, assessing risk factors, causative organisms, and graft outcomes.

All corneal transplants performed in Auckland from 2010 to 2022 were reviewed. Clinical records provided demographic data, graft type, compliance, follow-up, organisms cultured, antibiotic resistance, and transplant outcomes.

A total of 1184 keratoplasties (974 patients) were performed with mean follow-up of 4.2 years (IQR 1.8-7.9). Cumulative incidence of keratitis was 2.4% at one year and 6.0% at five years. Cases were bacterial (72.6%), viral (12.3%), fungal (5.4%), parasitic (2.7%) and autoimmune (6.8%). On multivariate analysis, Asian ethnicity (HR 8.76, 95% CI 6.2-9.6, p < 0.001), increasing age (HR 1.02, 95% CI 1.01-1.07, p = 0.012) and poor treatment compliance (HR 5.75, 95% CI 4.8-6.9, p < 0.001) were associated with increased risk. Anterior lamellar keratoplasty did not demonstrate increased risk (HR 0.50, 95% CI 0.37-1.04, p = 0.410), while endothelial keratoplasty reduced risk compared with penetrating keratoplasty (HR 0.17, 95% CI 0.02-0.4, p = 0.017). The rate of keratitis among endothelial grafts was 2.1% compared with 7.8% in penetrating keratoplasties. 7.9% of anterior lamellar keratoplasties developed keratitis, but this was not statistically significant (HR 0.50, 95% CI 0.37-1.04, p = 0.410). Keratitis significantly increased risk of graft failure compared with total graft failure rate (OR 2.5, 95% CI 1.8-3.6, p < 0.001). The COVID-19 pandemic period did not affect incidence (HR 1.00, 95% CI 0.9 -1.3, p = 0.104). Antibiotic resistance among bacterial isolates was low: 0% to vancomycin, 3.1% to tobramycin, 9.4% to ciprofloxacin/cephalosporins, and 25% to penicillin.

During a 12 year period with 1184 keratoplasties, the cumulative risk of keratitis increased substantially throughout the post-operative course, to affect 6% of transplants at five years. Fortunately, antibiotic-resistant organisms remain relatively uncommon in NZ. An episode of keratitis significantly increased the risk of corneal graft failure. Grafts performed in the COVID-19 pandemic era did not demonstrate an increased risk of keratitis. Compliance and the type of graft were the only potentially modifiable risk factors.