Rose Bengal Electromagnetic Activation with Green light for Infection Reduction II (REAGIR II) is a randomized, double-masked feasibility study. The purpose of this study is to determine differences in 6-month visual acuity between medical antimicrobial treatments alone versus antimicrobial treatment plus cross-linking with rose Bengal (RB-PDT).

Patients presenting to one of the Aravind Eye Hospitals in India or to the Federal University of São Paulo ophthalmology clinic in Brazil with smear-positive and/or culture positive typical (I.e. non-Nocardia or Mycobacteria) bacterial corneal ulcers and moderate to severe vision loss, defined as Snellen visual acuity of 20/40 of worse, will be eligible for inclusion. Those who agree to participate will be randomized to one of two treatment groups:

• Group 6, RB-PDT Plus Early Steroids: topical 0.5% moxifloxacin plus topical difluprednate 0.05% plus RB-PDT
• Group 7, Sham RB-PDT Plus Early Steroids: topical 0.5% moxifloxacin plus topical difluprednate 0.05% plus sham RB-PDT

Inclusion Criteria:

• Corneal ulcer that is smear positive and/or culture positive (within 24 hours) for typical bacteria (i.e. non-Nocardia or Myobacteria)
• Moderate to severe vision loss, defined as Snellen visual acuity of 20/40 (6/12) or worse
• Corneal thickness ≥350 µm, as measured on AS-OCT
• Age over 18 years
• Basic understanding of the study as determined by the physician
• Commitment to return for follow up visits

Exclusion Criteria:

• Evidence of concomitant infection on exam, gram stain, or confocal microscopy (i.e. herpes, both bacteria and acanthamoeba on gram stain)
• Impending or frank perforation at recruitment
• Involvement of sclera at presentation
• Presence of desmetocele at recruitment
• Non-infectious or autoimmune keratitis
• History of corneal transplantation
• History of intraocular surgery within the last three months*
• Pinhole visual acuity worse than 20/200 in the unaffected eye
• Participants who are decisionally and/or cognitively impaired