ESVO_SFEROV_Corneal-cross-linking_technique_and_veterinary applications_ Frank-Famose
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Presentation of technical aspects and applications of corneal-cross-linking in veterinary ophtalmology
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ESVO_SFEROV_Corneal-cross-linking_technique_and_veterinary applications_ Frank-Famose
- 1. CXL * Corneal collagen- cross-linking for veterinarians * Collagen Cross-Linking Dr Frank FAMOSE – DESV-ophta frankfamose@gmail.com Toulouse October 6th, 2016
- 2. Collagen reticulation by cross-linking A natural… or industrial… … or medical process
- 3. Collagen reticulation Anti-infectious effects Keratocytes apoptosis The photochemical process
- 6. The CXL in human ophthalmology Corneal ectasia: Progressive keratoconus Post-LASIK ectasia Pellucid marginal deg. Infectious keratitis: PACK-CXL Bullous keratopathy
- 7. The CXL in veterinary ophthalmology Infectious keratitis (dogs, cats, horses) Bullous keratopathy (dogs)
- 8. Keratomalacia « corneal melting » MMP imbalance Perforation Antibiotics & anticollagenases Tectonic surgery CXL
- 10. Results* 8 dogs 10 cats *Accelerated cross-linking
- 11. D1 D31 8/8 dogs – 10/10 cats 2/8 dogs – 3/10 cats Corneal vascularization
- 12. Corneal scar D1 D31 8/8 dogs – 10/10 cats
- 13. Discussion Clinical and pain improvement Direct effects of UVA Free oxygen radicals Physical changes within the cornea Biological corneal response
- 14. Adverse effects ? Infections Herpesvirus reactivation Endothelial alterations In humans No adverse effects attributable to the treatment
- 15. Ulcerative keratitis in Horses (Dr Hellander-Edman) 9 cases Ulcerative keratitis (Dresden protocol) 8 good results (1-3 months) 1 enucleation (fungal keratitis)
- 16. Worse than dogs and cats ? Corneal /epithelial thickness Depth of infection Low power UVA RF administration?
- 17. Protocol modifications Epithelium RF distribution UVA irradiation
- 18. Standard or accelerated ? Standard 3 mW/cm² 30 minutes « Flash » 30 mW/cm² 3 minutes 5,4 J/cm² Total duration ab. 1h20 Total duration ab. 40 min Same biological effects ? Same energy level
- 19. Iontophoresis Use of a low intensity continuous electric current to enhance the penetration of a ionized substance through a biological tissue
- 21. Bullous keratopathy Endothelial alterations Corneal edema Bullae and epithelial ulcers
- 22. « Epi-off » Stromal compaction UVA irradiation Hyperosmotic topical drugs RF + Dextran 20 % 9 mW/cm² 10 minutes Bullous keratopathy
- 23. Results Epithelial healing (<1 sem)
- 24. Conclusion Main indication : infectious keratitis 2 main constraints - High fluence - Minimal corneal thickness Secondary indication: Bullous keratopathy
- 25. Merci
Editor's Notes
- As you know, melting keratitis is a serious condition which is considered as an ocular emergency due to the high risk or corneal perforation. The melting of the cornea is due to metalloproteinase imbalance in relation with infectious or not infectious conditions. When the medical treatment, based on antibiotics and anticollagenases doesn’t succeed, surgery is indicated for tectonic purposes. Corneal collagen cross-linking is used for the treatment of infectious or melting keratitis in humans for some years and more recently for CN, CT and horses.
- Brachycephalic: dogs 18/32, cats 13/35. Failures: 5/25 with standard protocol. 3/43 w accelerated protocol. But ulcers in standard prot studies larger.
- Collagen cross-linking has been primarily developed for the treatment of human progressive keratoconus and all the protocols used are adapted from the conventional protocol. This consists in instillation of riboflavin during 30 minutes after removal of the epithelium and UV exposition for 30 minutes à 3 mW/cm². Modifications of this protocol have been proposed for 3 aims : preserving the epithelium, enhancing the riboflavin impregnation or shortening the exposition time by increasing the UV light intensity. Iontophoresis is a way of enhancing riboflavin impregnation.
- The principle of iontophoresis is to increase the penetration of a ionized substance through a tissue by the application of a constant electric current. It has been used for first time in ophthalmology in the beginning of the 20th century. Many studies have been conducted since 1990 for the delivery of many drugs in the eye (like steroids and so on). The first use of iontophoresis for riboflavin delivery was published recently for the treatment of keratoconus. For the moment, no veterinary clinical use of ionto has been described and no data for keratitis treatment is available.
- The iontophoresis device we have used has three parts : The corneal electrode is maintained on the corneal surface by suction and is filled with riboflavin till the grid is covered. The generator applies a constant current between the electrodes The return electrode which is connected to a needle inserted under the frontal skin.
- But in second step, we can imagine that if iontophoresis could enhance penetration of riboflavin, this process could work for other therapeutic agents like antibiotics. There’s a big work to do in this field and this is another story…
- Thank you for your attention. I’ll be happy to answer to any question.