Corneal cross-linking (CXL)-A clinical study to evaluate CXL as a treatment in comparison with medical treatment for ulcerative keratitis in horses

OBJECTIVE

Compare CXL treatment with medical treatment alone in horses with stromal, ulcerative keratitis.

ANIMALS STUDIED

24 horses (24 eyes) with stromal, ulcerative keratitis were included.

PROCEDURE

12 horses were initially treated with CXL, and 12 horses were given conventional medical treatment. Topical medical treatment was added to horses in the CXL group if necessary. Parameters including cytology, microbial growth, time to fluorescein negativity, and time to inhibition of stromal melting were evaluated.

RESULTS

After the first day of treatments, a decrease in inflammatory signs and pain from the eye was observed in both groups. Stromal melting ceased within 24 hours regardless of treatment. CXL treatment alone was sufficient in 3 horses with noninfectious, superficial stromal ulcerations. Clinical signs of impaired wound healing were seen after 3-14 days in corneas with suspected or proven bacterial infection treated with CXL only, most likely because of insufficient elimination of bacteria deeper in the corneal stroma or because of re-infection from bacteria in the conjunctiva. The average decrease in stromal ulcer area per day after onset of treatment was almost identical between the groups, and no significant difference in time to fluorescein negativity was found.

CONCLUSIONS

We consider CXL a possible useful adjunct treatment of corneal stromal ulcers in horses, especially for melting ulcers and as a potential alternative to prophylactic antibiotic treatment for noninfected stromal ulcers. However, CXL should not be used alone for infected or suspected infected stromal ulcers, because topical antibiotics were required in all horses with proven infectious keratitis.

Corneal cross-linking in 9 horses with ulcerative keratitis

BACKGROUND

Corneal 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.

RESULTS

Nine 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.

CONCLUSIONS

CXL 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.

Changes in some biochemical indicators of bone turnover after ultraviolet irradiation of dairy cows

The effect of ultraviolet irradiation on some biochemical indicators of bone turnover in dairy cows was determined. The irradiation was performed using a stationary system for two months and comprised a regimen of 10 days irradiation followed by 10 days rest. After ultraviolet irradiation, significant differences in the activities of serum alkaline phosphatase (P < 0.001) and bone alkaline phosphatase isoenzyme (P < 0.05) and concentration of osteocalcin (P < 0.01) were demonstrated. The results suggest that supplementary ultraviolet irradiation during winter could be used as a simple but reliable method of preventing the development of generalised metabolic bone disorders in dairy cows.

[Effect of UV radiation and the autotransfusion of UV-irradiated blood on the content of cationic proteins in the neutrophilic granulocytes of calves]

A study was made of the influence of UV-irradiation (254 nm) of blood in vitro, of the autotransfusion of UV-irradiated blood (AUVIB), and of the mixture of UV-irradiated and intact blood in vitro on the content of bactericidal cation proteins (CP) in blood neutrophil of calves suffered from dyspepsia and broncho-pneumonia. Age differences were noticed in CP contents and their decrease in neutrophils following AUVIB in vivo and administration of the mixture of blood in vitro. The decrease in cell CP contents is presumably due to neutrophil degranulation and CP release into the blood plasma. Since the initial mechanisms of neutrophil degranulation are located on the cell surface, the CP release is supposed to result from a membranotropic effect of UV-irradiated blood on the intact autologous blood. This effect may explain the increase in nonspecific resistance of organism after the AUVIB, being one of the main therapeutic phenomena of the AUVIB-therapy.