Texas Equine Veterinary Association Publications
Issue link: http://aspenedgemarketing.uberflip.com/i/1226337
www.texasequineva.com • 8 Corneal abrasions are the most common eye condition treated in horses. While many heal without consequence, several pathogens and diseases will threaten the globe and vision. The equine cornea is thickest centrally and thinnest at the limbus. The stroma is the most dominant component of the cornea. It comprises about 90% of the corneal thickness and is mainly composed of fibers of collagen type I. When epithelial healing fails, a corneal ulcer is produced. Plasmin produced in response to the ulcer leads to production of matrix metalloproteinases (MMPs). Cytokines, prostaglandins, and leukotrienes are released by the keratocytes and epithelial cells. Leukocytes are recruited and release proteolytic enzymes that can destroy the cornea. While many treatments are targeted at eliminating the bacteria and fungus that infect the cornea and at controlling the pain, the production of the proteolytic enzymes leads to significant damage. In some cases the damage can perforate the cornea and destroy the eye. Therapies targeted at the proteolytic enzymes include serum, EDTA, tetracyclines, amnion, acetyl cysteine, and ilomostat, among others. A new technique is being used to stiffen the cornea and reduce the melting. Corneal collagen cross-linking (CXL) is a technique that develped to stiffen the cornea in keratoconus (progessive corneal thinning) in people. It has been adapted to use as an adjunct treatment in infected keratitis in people as well as veterinary medicine (BMC Vet Res. 2013). Cross-linking is the formation of bonds between molecular chains. By saturating corneal tissue with riboflavin and subsequently activating it with ultraviolet light (UVA 365 nm), reactive oxygen species are produced (Biophys J. 2006) and the degree of cross-linking in the corneal stroma is increased (Invest Ophthalmol Vis Sci. 2010), increasing the corneal rigidity. Additionally, binding sites for collagenase enzymes are altered thereby decreasing the effect of collagen degredation by Ben Buchanan, DVM, DACVIM, DACVECC ABOUT THE AUTHOR Dr. Ben Buchanan grew up in Navasota, Texas. He went to Texas A&M and graduated from there with his DVM in 2001. Afterward, he completed two residencies; Large Animal Internal Medicine at University of Tennessee, Knoxville, in 2004, and Emergency and Critical Care at University of Pennsylvania in 2005. Ben is one of the very few people in the world to be board certified in Internal Medicine and Emergency Critical Care. Ben joined BVEH Navasota in 2005, where he works alongside his father, T-Bone. He is also active in community outreach by speaking at meetings and events around the world regarding equine care. Ben is married to the lovely Shana, whom he met in veterinary school. Shana is a small animal veterinarian and owner of Lake Conroe Vet Group. They have two children, Jane Marie and Terrell. Contact: ben.buchanan@bveh.com melting corneal ulcers new treatment for