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

Corneal Ulcers in Critically Ill Foals in Intensive Care: Case Series of Standard Treatment and Corneal Cross-Linking

Riboflavin/UV-A corneal cross-linking (CXL) has been applied to treat corneal ulcers in adult horses, but its use in critically ill neonatal foals has not been described. Five cases of hospitalized, critically ill neonatal foals that were in intensive care with corneal ulcers, the ophthalmic treatment, and their outcome up to 1 year are described. A single treatment of CXL phototherapy was performed in three of five foals (five eyes). The application of a riboflavin ophthalmic solution for 20 minutes was followed by the UV-A light irradiation at 30 mW/cm2 for 3 minutes. Topical antibiotic administration was withdrawn after CXL. Two other foals received standard treatment. Descriptions of ocular lesions, fluorescein staining, and photographic documentation were recorded. The visual outcome, corneal transparency, and aesthetics, as well as healing time were evaluated in the follow-up. The frequency of topical medication considerably decreased in cases treated with CXL. Corneal opacity and pain decreased within 3 days following CXL. In the foals treated with CXL, the ulcers healed (fluorescein stain negative) in 24, 28, and 35 days after the onset of clinical signs and 10, 15, and 21, after CXL. No fibrosis or corneal scars were found in the cases treated with CXL. The two standard treatment cases healed after 26 and 36 days respectively. Corneal cross-linking may be an additional or alternative treatment of corneal ulcers in critically ill neonatal foals and may reduce the use of antibiotics.

In vitro susceptibility of canine corneal bacterial pathogens to three cross-linking protocols

OBJECTIVE

To assess in vitro antibacterial efficacy of three cross-linking (XL) protocols on bacteria associated with canine ulcerative keratitis.

METHODS

Three XL protocols: UVA 3 mW/cm² for 60 min, UVA 3 mW/cm² for 30 min, and UVA 30 mW/cm² for 3 min with and without application of riboflavin and a riboflavin-only protocol were performed in vitro on the four most common bacterial genera isolated from cases of canine ulcerative keratitis treated at Dick White Referrals, UK. Zones of bacterial growth inhibition (GIZ) associated with treatment were measured and compared.

RESULTS

The four most common isolates were Pseudomonas aeruginosa (PA) (48/140, 34.3%), Streptococcus spp. (32/140, 22.9%), Staphylococcus spp. (24/140, 17.1%) and Escherichia coli (EC) (11/140, 7.9%). PA, EC, Streptococcus canis (SC), and Staphylococcus pseudintermedius (SP), isolated from canine corneas, were selected for testing. EC and SC demonstrated growth inhibition following all UVA/riboflavin protocols. PA and SP only displayed growth inhibition following the 60 min UVA/riboflavin protocol. GIZ areas for 60 min UVA/riboflavin protocols were significantly greater than 30 and 3 min UVA/riboflavin protocols (p < .01) and there was no significant difference between 30 and 3 min UVA/riboflavin protocols. In respect to GIZ areas, EC was significantly more susceptible to XL than SP (p = <.01).

CONCLUSIONS

All UVA/riboflavin XL protocols caused growth inhibition of EC and SC in vitro. PA and SP did not show clear growth inhibition in vitro following exposure to XL protocol settings of UVA 3 mW/cm² for 30 min and UVA 30 mW/cm² for 3 min.

Melting corneal ulcers (keratomalacia) in dogs: A 5-year clinical and microbiological study (2014-2018)

OBJECTIVES

To identify bacterial microorganisms associated with canine keratomalacia, review their antimicrobial sensitivity, and evaluate clinical outcomes compared to results of microbial culture.

METHODS

Retrospective analysis of clinical records of dogs diagnosed with a melting corneal ulcer presented to a referral hospital in Hertfordshire, UK between 2014 and 2018.

RESULTS

One hundred and ten melting corneal ulcers were sampled in 106 dogs. The most common pure bacterial isolate was Pseudomonas aeruginosa (n = 26) followed by β-hemolytic Streptococcus (n = 12). Melting corneal ulcers that cultured coagulase-positive Staphylococcus, coliform bacteria, Pasteurella multocida, Enterococcus, and Streptococcus viridans presented in smaller numbers and were analyzed together (n = 16). Multiple cultures were identified in nine cases (n = 9). Forty-seven cultures yielded no bacterial growth (n = 47). The susceptibility to fluoroquinolones remained high with the exception of β-hemolytic Streptococci. There was no significant difference in the ulcer severity at presentation in regard to the cultured bacteria. Overall, 63 eyes (57%) received surgical grafting in addition to medical treatment. In 14 cases (13%), the progression of corneal melting despite medical ± surgical treatment resulted in enucleation. Fifty-seven percent (8/14) of the enucleated eyes cultured pure Pseudomonas aeruginosa isolates. In contrast, all β-hemolytic Streptococcus-associated ulcers healed.

CONCLUSIONS

The most common bacterial species associated with canine keratomalacia were Pseudomonas aeruginosa and β-hemolytic Streptococcus. Because of the variation in antibacterial sensitivity between these two species, bacterial culture and sensitivity testing should be performed in all dogs presenting with keratomalacia. Melting corneal ulcers associated with pure Pseudomonas infection were significantly more likely to result in globe loss than melting corneal ulcers associated with other cultures.

An Assay System to Evaluate Riboflavin/UV-A Corneal Phototherapy Efficacy in a Porcine Corneal Organ Culture Model

Simple summary

The scope of this study is to quantitatively evaluate, with an automated digital image analysis method, the efficacy of riboflavin/UV-A corneal phototherapy on the cornea in a porcine corneal organ culture model of ulcerative melting keratitis. Riboflavin/UV-A corneal phototherapy provided a favorable outcome in the corneal wound healing process after chemical injury: the treatment restores the damaged corneas to the texture of healthy corneas. This automated image analysis method may be compared to clinical diagnostic methods, such as optical coherence tomography (OCT) imaging, for in vivo damaged ocular structural investigations. Positive results from this research could provide an opportunity for studying the effects of this method in other economically and emotionally valued species, such as dogs, cats, and horses. The relatively overall low treatment cost and the ease of performing the procedure make riboflavin/UV-A corneal phototherapy accessible to the veterinary market.

Abstract

The purpose of this study was to investigate the response of porcine corneal organ cultures to riboflavin/UV-A phototherapy in the injury healing of induced lesions. A porcine corneal organ culture model was established. Corneal alterations in the stroma were evaluated using an assay system, based on an automated image analysis method able to (i) localize the holes and gaps within the stroma and (ii) measure the brightness values in these patches. The analysis has been performed by dividing the corneal section in 24 regions of interest (ROIs) and integrating the data analysis with a “multi-aspect approach.” Three group of corneas were analyzed: healthy, injured, and injured-and-treated. Our study revealed a significant effect of the riboflavin/UV-A phototherapy in the injury healing of porcine corneas after induced lesions. The injured corneas had significant differences of brightness values in comparison to treated (p < 0.00) and healthy (p < 0.001) corneas, whereas the treated and healthy corneas showed no significant difference (p = 0.995). Riboflavin/UV-A phototherapy shows a significant effect in restoring the brightness values of damaged corneas to the values of healthy corneas, suggesting treatment restores the injury healing of corneas after lesions. Our assay system may be compared to clinical diagnostic methods, such as optical coherence tomography (OCT) imaging, for in vivo damaged ocular structure investigations.