Outcomes of Post-Keratoplasty Microbial Keratitis: A 16-Year Analysis

<b>Purpose:</b> To determine the incidence, risk factors (including systemic immunosuppression), and outcomes of microbial keratitis in corneal transplants over a 16-year observation period at a tertiary referral hospital in Poland. <b>Methods:</b> This retrospective cohort study included 125 episodes of infectious keratitis in 117 patients who underwent corneal transplantation between 2008 and 2023 at the Department of Ophthalmology, Medical University of Warsaw, Poland. The data collected included demographics, indications for transplantation, infection rates, risk factors, best-corrected visual acuity (BCVA) at presentation and discharge, changes in visual acuity, and treatments received prior to hospital admission. Clinical signs, symptoms, diagnostic tests, and management strategies were also reviewed. Additionally, the outcomes of surgical interventions, such as therapeutic corneal transplantation and evisceration, were examined. <b>Results</b>: Among the 2869 corneal transplants performed over the 16-year period, the incidence of post-keratoplasty microbial keratitis (PKMK) was 4.35%. The most common indication for transplantation in affected patients was an active infection unresponsive to medical therapy (n = 62, 52%). One-third of PKMK cases occurred in patients with repeat transplants. Median visual acuity prior to infection was 1.6 logMAR, worsening to 2.3 logMAR at presentation. Following treatment, visual acuity improved to a median of 1.9 logMAR at discharge, with no significant improvement by the one-year follow-up. At that time, 75.1% of patients remained legally blind (BCVA ≤ 20/200); 21% recovered to pre-infection visual levels, while 46% experienced additional visual loss due to PKMK. Multivariate regression identified corneal perforation and systemic immunosuppression as independent predictors of poorer visual outcomes (<i>p</i> < 0.001 and <i>p</i> = 0.03, respectively. <b>Conclusions</b>: Microbial keratitis in corneal grafts is associated with poor long-term visual outcomes. At one year post-infection, the median BCVA was 1.9 logMAR, with 75.1% of patients remaining legally blind. Nearly half of the cohort experienced additional visual loss compared to their pre-infection status, underscoring the severity of PKMK and the need for vigilant postoperative care.