Our experience based on the above and other cases suggest that CXL could be an effective tool in battling difficult cases of infectious keratitis. This treatment could present many advantages but will need further investigation.

This trial illustrates that photosensitization of riboflavin using UVA at 365 nm has the potential to induce healing in patients with microbial keratitis. The results from the treatment of these 16 patients with corneal ulcers indicate that UVA-riboflavin photochemical therapy merits a controlled study in order to assess its efficacy and safety compared to antibiotics.

Riboflavin photo-activation using UVA (365 nm) can achieve an extensive eradication of bacteria, and the combination is more potent in reducing bacterial number than UV alone.

BackgroundCorneal ulcers are one of the most common eye problems in the horse and can cause varying degrees of visual impairment. Secondary infection and protease activity causing melting of the corneal stroma are always concerns in patients with corneal ulcers. Corneal collagen cross-linking (CXL), induced by illumination of the corneal stroma with ultraviolet light (UVA) after instillation of riboflavin (vitamin B2) eye drops, introduces crosslinks which stabilize melting corneas, and has been used to successfully treat infectious ulcerative keratitis in human patients. Therefore we decided to study if CXL can be performed in sedated, standing horses with ulcerative keratitis with or without stromal melting.ResultsNine horses, aged 1 month to 16 years (median 5 years) were treated with a combination of CXL and medical therapy. Two horses were diagnosed with mycotic, 5 with bacterial and 2 with aseptic ulcerative keratitis. A modified Dresden-protocol for CXL could readily be performed in all 9 horses after sedation. Stromal melting, diagnosed in 4 horses, stopped within 24 h. Eight of nine eyes became fluorescein negative in 13.5 days (median time; range 4–26 days) days after CXL. One horse developed a bacterial conjunctivitis the day after CXL, which was successfully treated with topical antibiotics. One horse with fungal ulcerative keratitis and severe uveitis was enucleated 4 days after treatment due to panophthalmitis.ConclusionsCXL can be performed in standing, sedated horses. We did not observe any deleterious effects attributed to riboflavin or UVA irradiation per se during the follow-up, neither in horses with infectious nor aseptic ulcerative keratitis. These data support that CXL can be performed in the standing horse, but further studies are required to compare CXL to conventional medical treatment in equine keratitis and to optimize the CXL protocol in this species.

UVA-riboflavin settings used in PACK-CXL are effective in reducing both antibiotic-resistant and non-resistant bacteria. Antibiotic resistance does not appear to be protective against the photooxidative exposure.