Novel Treatment of Infectious Keratitis in Canine Corneas Using Ultraviolet C (UV-C) Light

Objective: To investigate the therapeutic effect of 275 nm wavelength ultraviolet C (UV-C) light for treatment of bacterial keratitis in canine corneas using an affordable, broadly available modified handheld device.

Methods: UV-C therapy (UVCT) was evaluated in two experiments: in vitro using triplicates of three bacterial genera (Staphylococcus, Streptococcus, Pseudomonas spp., and a mix of all species) where the UVCT was performed at a distance of 10, 15, and 20 mm with 1 or 2 doses (4 h apart) for 5, 15, or 30 s; ex vivo model where healthy canine corneal buttons were inoculated superficially and deep (330 μm) with the same bacterial isolates and treated at a 10 mm distance for 15 s with one dose of 22.5 mJ/cm. Fluorescent marker (STYO9-PI) was used to label (green = live bacteria, red = dead bacteria), and confocal microscopy was used to image the bacteria.

Results: In vitro results showed all plates treated with UVCT had 100% bactericidal effect for all isolates with single dose of 15 s at 10 mm distance or two doses, 4 h apart at 15 mm and was ineffective with single dose at 15-20 mm. The ex vivo results confirmed a significant decrease in bacterial load for all isolates on samples inoculated superficially but were inconclusive for intrastromal ones.

Conclusions: UVCT confirmed the therapeutic potential for all tested isolates, for both in vitro and ex vivo experiments using a single exposure of 15 s. While safety studies are underway, clinical trials are warranted.