Rose Bengal Photodynamic Therapy (Rb-Pdt) As A Potential Adjuvant Management For Severe Infectious Keratitis

Infectious keratitis (IK) is a leading cause of global blindness and a medical emergency that can result in corneal perforation and endophthalmitis. With rising antimicrobial resistance and limited access to donor tissue for therapeutic keratoplasty (T-PKP) in developing countries, alternative treatments are vital. The primary objective of this study was to evaluate the clinical outcomes, microbiological profile, and efficacy of Rose Bengal Photodynamic Therapy (RB-PDT) as an adjunctive therapy in patients presenting with severe, recalcitrant infectious keratitis.

Prospective, noncontrolled, interventional study at the Instituto de Oftalmologia Fundacion Conde de Valenciana IAP in Mexico City, Mexico, from March 2023 to December 2025. All patients enrolled in the study participated voluntarily after reading and signing a written informed consent, previously reviewed and approved by our institution's committees of ethics, research, and biohazards, following the tenets of the Declaration of Helsinki.

Patients > 18 y/o with severe IK (bacterial, fungal, or protozoan) were enrolled. Severity was defined by: central ulcer, large infiltrate (>3mm), melting, hypopyon. clinical deterioration despite two weeks of conventional medical therapy. Cultures were identified via VITEK and Kirby-Bauer. The RB-PDT procedure involved 8mm de-epithelialization, 0.1% Rose Bengal application for 30 min, and green LED irradiation (525nm, 6mW/cm²) for 15 min (5.4 J/cm² dose). Follow-up lasted up to 15 months. Success was defined as clinical resolution without therapeutic keratoplasty (T-PKP); failure was defined as progression to perforation or evisceration.

46 eyes were included, with a success rate of 65.2% (mean follow-up 8 months). Mean time to resolution in successful cases: 53.6 ± 20.4 days.Fusarium spp. (23.9%) and Pseudomonas spp. (15.2%) were the most common isolates. Fungal infections accounted for 32.6% of cases.The microorganism with the highest failure rate was Fusarium spp. (40%). Clinical failure was significantly associated with the presence of a fungal ball in the anterior chamber (OR: 9.0), a delay in RB-PDT application exceeding 30 days from symptom onset (OR: 5.14), and specific bacterial etiologies. Additional interventions: 16 eyes (34.8%) required T-PKP due to treatment failure. After resolution, 7 successful cases underwent elective optical PKP for visual rehabilitation.

Our findings suggest that RB-PDT is a potential adjuvant in the treatment of severe infectious keratitis. It could help shorten clinical resolution time and reduce the need for T-PKP.