Evaluating Medical Therapy Failure in Microbial Keratitis: Risk Factors and Management Alternatives

To describe the treatments used in cases of infectious keratitis and determine the risk factors associated with treatment failure, including prolonged infection duration, treatment modifications, and the need for surgical intervention.

This retrospective case series includes culture-proven microbial keratitis cases treated in nine hospitals in the region of Galicia, Spain, between 2010 and 2020.

A total of 654 patients were included. Prolonged infection duration was associated with factors such as advanced age, deep infiltrates, corneal thinning, and large epithelial defects. Initial empirical treatment was modified in 204 cases (31.2%), with 113 cases requiring changes due to antibiotic resistance and 88 cases due to clinical deterioration. Polymicrobial infections, contact with vegetable matter, previous herpetic keratitis, and topical steroid use were identified as risk factors for treatment modification. Surgical intervention was required in 142 cases (21.7%). Among these, 50 patients (7.6%) underwent evisceration, 43 (6.6%) received amniotic membrane transplantation, and 37 (5.7%) underwent tectonic penetrating keratoplasty. Previous keratoplasty, prior herpetic keratitis, topical steroid use, and large epithelial defects were also significant risk factors for surgical intervention.

Treatment failure in cases of microbial keratitis (MK) may be influenced by systemic factors, such as advanced age, and ocular factors, including large epithelial defects, deep infiltrates, polymicrobial infections, contact with vegetable matter, and previous topical steroid use. Identifying these risk factors is essential for guiding empirical treatment and recognizing refractory ulcers that may require more intensive management, including surgical intervention.