Evaluation of Toluidine Blue-Mediated Photodynamic Therapy for Experimental Bacterial Keratitis in Rabbits

OBJECTIVE: The objective of this study was to evaluate the effect of toluidine blue-mediated photodynamic therapy on experimental bacterial keratitis in rabbits. METHODS: Bacterial keratitis was induced in rabbits by the injection of 200 μl Staphylococcus aureus (S. aureus) solution into the anterior stroma of the right cornea. Rabbits were randomly divided into four groups: toluidine blue O and red light (TBOR), levofloxacin eye drops (LEV), the combination of TBOR and LEV (TBOR + LEV), and a control group. Clinical manifestations, histopathology, and transmission electron microscopy were analyzed at various time points. RESULTS: Conjunctival injection and surface area of the corneal ulcer in the TBOR group and the TBOR + LEV group showed significant improvement from baseline after 7 days of treatment. Compared to baseline, the depth of corneal infiltration was decreased at day 14 in the TBOR and TBOR + LEV groups. Microscopic analysis of the TBOR and TBOR + LEV groups showed that the structure of each layer was intact, and there were no inflammatory cells in the corneal stroma. Additionally, IL-1β and TNF-α were highly expressed in the LEV and control groups but were lower in the TBOR and TBOR + LEV groups. Under transmission electron microscopy, the corneas in the TBOR and TBOR + LEV groups were intact, whereas in the LEV and control groups, double-walled structures corresponding to S. aureus were found in the superficial stromal layer. CONCLUSIONS: TBOR demonstrated in vivo antibacterial efficacy against S. aureus. TRANSLATIONAL RELEVANCE: This study found in vivo antibacterial efficacy of toluidine blue-mediated photodynamic therapy on rabbit experimental bacterial keratitis, thus providing an additional new option for clinical treatment of bacterial keratitis.