Long-Term Assessment of Rose Bengal Photodynamic Therapy in Infectious Keratitis: Insights from the REAGIR Randomized Trial

Highlight

• Rose bengal photodynamic therapy (RB-PDT) with green light was evaluated as adjunctive treatment for fungal, acanthamoeba, and smear/culture-negative infectious keratitis.
• The 12-month follow-up from the multicenter, randomized REAGIR trial demonstrated no significant improvement in best spectacle-corrected visual acuity (BSCVA) compared to sham treatment.
• No reduction in scar size or rates of corneal perforation and therapeutic penetrating keratoplasty was observed with RB-PDT.
• Findings reinforce prior 6-month results, highlighting the need for alternative therapies or photosensitizers for infectious keratitis.

Study Background

Infectious keratitis, a severe corneal infection caused by fungi, protozoa such as acanthamoeba, or bacteria, remains a major cause of visual morbidity worldwide. Despite intensive antimicrobial therapy, outcomes frequently include persistent scarring, corneal perforation, and vision loss. New adjunctive treatments that can reduce microbial load and improve clinical outcomes are urgently needed given the rising incidence of resistant pathogens and diagnostic challenges in smear/culture-negative cases. Photodynamic therapy (PDT) has emerged as a novel approach, leveraging light-activated photosensitizers to generate reactive oxygen species that inactivate pathogens. Rose bengal, a dye with known antimicrobial properties upon activation by green light, has shown promise in preliminary studies; however, long-term controlled clinical data are lacking.

Study Design

The REAGIR trial was a rigorous international multicenter, randomized, double-masked, sham-controlled clinical study conducted at Aravind Eye Hospitals in India and the Federal University of São Paulo in Brazil. A total of 330 adult patients with corneal ulcers were enrolled and randomized to receive either adjunctive rose bengal photodynamic therapy (RB-PDT) or an identical sham procedure without green light activation. Participants in both groups continued to receive standardized antimicrobial therapy tailored to clinical and microbiological findings, including fungal, acanthamoeba, and smear/culture-negative infections. The RB-PDT protocol involved application of 0.1% rose bengal topically followed by 15 minutes of green light irradiation. The primary outcome was the best spectacle-corrected visual acuity (BSCVA) measured as logarithm of the minimum angle of resolution (logMAR) at 6 months; secondary outcomes included 12-month BSCVA, infiltrate and/or scar size, corneal perforation (CP), therapeutic penetrating keratoplasty (TPK) rates, and microbiological cure at 12 months. Data were analyzed between June and July 2025.

Key Findings

Out of 330 participants (mean age 50 years, 65% male), 282 had evaluable BSCVA data and 250 had 12-month infiltrate/scar measurements. At 12 months, the mean difference in BSCVA between RB-PDT and sham was 0.01 logMAR (95% CI, -0.13 to 0.14; P=0.91), indicating no significant improvement in visual acuity with adjunctive therapy. Similarly, scar size differences were negligible (mean difference 0.006 mm; 95% CI, -0.32 to 0.33; P=0.97). Rates of corneal perforation or the need for therapeutic penetrating keratoplasty were comparable between groups (31 events in RB-PDT vs 34 in sham; hazard ratio 1.21; 95% CI, 0.74–1.98; P=0.44). No subgroup demonstrated differential treatment benefits by causative organism.

The safety profile was acceptable with no excess adverse events attributable to the photodynamic procedure. Microbiological cure rates at 12 months did not differ significantly between the two groups, further suggesting the lack of antimicrobial advantage under the study conditions.

Expert Commentary

This well-powered, methodologically robust trial provides critical evidence addressing the long-term efficacy of rose bengal photodynamic therapy in infectious keratitis. Despite the theoretical antimicrobial mechanism and encouraging laboratory data, clinical translation appears limited, with no demonstrated benefit in visual recovery, scar reduction, or complication prevention at 12 months. Prior shorter-term data from the same trial at 6 months concord with these findings, reinforcing the conclusion that RB-PDT, as applied in this protocol, does not augment standard medical therapy.

Potential reasons include limited penetration of rose bengal or green light into deeper corneal layers, insufficient reactive oxygen species generation, or suboptimal photosensitizer dosing and light parameters. Additionally, infectious keratitis complexity involving diverse pathogens and host immune responses may not be adequately addressed by this single modality. The trial’s exclusion of other photosensitizers or alternative light sources leaves open the possibility that different photodynamic algorithms may yield improvements.

From a clinical standpoint, these results caution against routine clinical adoption of RB-PDT for infectious keratitis outside of research contexts. Ongoing exploration of combined antimicrobial and photodynamic approaches with optimization of parameters and patient selection will be crucial. Moreover, the study underscores the challenge of improving outcomes in infectious keratitis, necessitating innovation in diagnostics, therapeutics, and adjunctive care.

Conclusion

The 12-month follow-up data from the REAGIR randomized clinical trial clearly indicate that adjunctive rose bengal photodynamic therapy with green light does not improve long-term clinical outcomes in infectious keratitis when added to standard antimicrobial treatment. There was no benefit observed in visual acuity, scar size, or rates of severe complications such as corneal perforation or need for penetrating keratoplasty.

These findings validate previous 6-month results and underscore the need for alternative therapeutic strategies, whether through different photosensitizers, refined photodynamic protocols, or entirely new adjunctive modalities. The study sets a high standard for evidence-based evaluation in ophthalmic infections and provides a valuable reference for clinicians and researchers aiming to mitigate the global burden of infectious keratitis.

Funding and Trial Registration

The REAGIR trial was funded by supporting institutions affiliated with participating centers. The trial is registered at ClinicalTrials.gov under identifier NCT05110001.

Reference

Prajna NV, Bernard A, Prajna L, Rajaraman R, Sharma SS, Christy J, Radhakrishnan N, Mandlik K, De Freitas D, Höfling-Lima AL, Varnado NE, Abdelrahman S, Arnold BF, Lietman TM, Rose-Nussbaumer J, REAGIR Research Group. Rose Bengal Electromagnetic Activation With Green Light for Infection Reduction: Follow-Up of a Randomized Clinical Trial. JAMA Ophthalmol. 2026 Jun 25. PMID: 42348235. https://pubmed.ncbi.nlm.nih.gov/42348235/