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.

An overview of corneal collagen cross-linking (CXL)

Corneal collagen cross-linking (CXL) was first described over a decade ago and is now considered to be one of the most important surgical innovations of modern ophthalmology. Prior to its introduction, no interventions were available to arrest, or slow down ectatic disease progression, with corneal transplantation required in the majority of cases. Unlike earlier treatments of corneal ectasias that attempted to only improve the consequences of the disease, CXL aims to address the corneal biomechanical weakening itself. The long-term safety and efficacy of CXL have been established in several studies that have documented significant improvements in all outcome measures (visual acuity, spherical equivalent, astigmatism, and keratometric findings). The emerging combination of CXL with other interventions (termed 'CXL plus') optimizes the visual and topographic outcomes. This, along with the expansion of the techniques' indications for other clinical conditions, such as microbial keratitis, highlights the continuous improvement of the initial technique and confirms its wide acceptance. Overall, CXL has already demonstrated much promise and has several clinical indications, representing a clear example of recent advances in ocular therapy.

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.

[Irradiation of cornea with ultraviolet light and riboflavin administration as a new treatment for erosive corneal processes, preliminary results in four patients]

BACKGROUND

Corneal melting is a serious condition and in many cases maybe managed only by surgery. UV-radiation with Riboflavin is a new method that may stop the melting process of the cornea.

PATIENTS AND METHOD

Four patients suffering from melting ulcera of the cornea of various origin underwent a single UV-radiation. Two ultraviolet diodes were used emitting light with an wavelength of 370 nm with an energy of 2.5 mW/cm2. The radiation time was 30 minutes. Before he radiation was performed 2-3 drops of 0.11% Riboflavinsolution were applied to the cornea. The treatment area was 6-7 mm in diameter.

RESULTS

After the treatment in three of the four patients the melting process of the cornea stopped. At least temporarily, a surgical procedure could be delayed.

CONCLUSION

Because of the absence of any side-effects in serious cases the method is recommended prior to surgery.

[Low-intensity helium-neon laser irradiation in multimodal treatment of corneal injuries]

He-Ne laser stimulation was used in multiple-modality treatment of 512 patients with various corneal conditions: 217 with perforating wounds, 75 with chemical and thermal burns, 48 with ulcers of various origins, and 162 with endothelial-epithelial dystrophy resulting from cataract extraction with implantation of the intraocular lens. A course of treatment consisted of 6 to 10 daily 3 min exposures at radiation power density of 50-100 micro W/cm2 on the cornea. The effect achieved by laser stimulation was significantly superior to that of routine methods of treatment used in the reference groups. He-Ne laser stimulation was conducive to a sooner reduction of the inflammatory processes, to recovery of the corneal sensitivity and epithelialization, and to shortening hospital treatment.