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YOUR GUIDE TO THE 2017 AAEP CONVENTION SPONSORED BY A41 TheHorse.com/AAEP2017 March 2018 THE HORSE AAEP Wrap-Up 'Angry' Corneas and ERU STACEY OKE, DVM, MSC How to Manage 6 Types of Corneal Ulcers orneal ulcers are the most common ophthalmic condition equine practitioners see in the field. Some are simple scratches that heal quickly with appropriate treatment, while others are more complex, involve infection, and can take longer to heal. Regardless of their severity, they must be managed appropriately to prevent/treat infection, control pain, and speed healing. "When an ulcer is slow to heal, one must carefully examine the eye to deter- mine what kind of ulcer you are dealing with," said Catherine Nunnery, DVM, Dipl. ACVO, a large animal ophthalmolo- gist at the University of Pennsylvania School of Veterinary Medicine, in Ken- nett Square. Classifying ulcers correctly ensures timely application of appropriate therapy. Nunnery said there are six types of equine corneal ulcers: 1. Nonhealing (indolent) ulcers , which occur due to abnormal adhesion of corneal epithelial cells to the anterior stroma (the layer of tissue beneath the outer surface of the cornea); 2. Corneal mineralization due to calcium deposits. Patients with this type of ulcer have either recurrent anterior (front of the eye) uveitis or chronic/ recurrent keratitis (corneal inflamma- tion). The calcium deposits appear as multiple white opacities in horizontal patterns across the central or ventral (lower) cornea; 3. Eosinophilic keratitis , which research- ers believe results from exposure to either an allergen or parasites. One or both eyes can be involved. Fluorescein staining (a test that uses dye to detect corneal damage) results can be faint and potentially missed without the use of a cobalt blue light. Cytology (viewing cells under a microscope) performed on corneal scapings reveals eosino- phils—a type of white blood cell that responds to allergic and/or parasitic stimuli— often without evidence of infection in a relatively nonpainful eye; 4. Corneal edema , characterized by fluid in the stromal layer. These occur because either the corneal ulcer allows fluid to reach the stroma or dysfunc- tion of the deepest layer of the cornea (e.g., glaucoma) causes fluid buildup in the stroma and ulcers to form; 5. Corneal infection , most commonly caused by bacteria (Staphylococcus, Streptococcus, Pseudomonas) and fungi (Aspergillus, Fusarium), and; 6. Keratomalacia and stromal loss, the dreaded melting ulcer. Veterinarians treat the first four types of ulcers similarly; therapy generally involves administering systemic non- steroidal anti-inflammatory drugs (e.g., phenylbutazone or flunixin meglumine equivalent); the cycloplegic atropine to re- lieve ciliary spasm, which is essentially a "charlie horse" in the muscle that controls pupil dilation; antibiotics effective against both Gram-positive and -negative agents; antifungal agents; and antiproteases such as serum or ethylenediaminetetraacetic acid (more simply called EDTA). As your veterinarian will warn you, never use any ocular medication containing a cortico- steroid to treat ulcerated corneas. In some cases, a veterinarian might need to remove the damaged tissue using a process called debridement. "The underlying cause of ulcers can be very difficult to ascertain," said Nunnery, adding that corneal cytology plays a key role in diagnosing and treating it. ERU: Your Best Chance for Successful Treatment Equine recurrent uveitis (ERU) is a nasty disease, causing searing pain and BIANCA MCCARTY COURTESY DR. CATHERINE NUNNERY One type of corneal ulcer is corneal mineraliza- tion due to calcium deposits.