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YOUR GUIDE TO THE 2017 AAEP CONVENTION SPONSORED BY A42 TheHorse.com/AAEP2017 AAEP Wrap-Up THE HORSE March 2018 loss of use. Adding insult to injury, the disease keeps coming back, often result- ing in blindness. This condition frequently frustrates vet- erinarians such as Mary Lassaline, DVM, PhD, MA, Dipl. ACVO—even to the point of despair, she said—because it remains expensive and unrewarding to treat. But as researchers learn more about the ins and outs of ERU, they're finding ways to improve treatment. "ERU is the No. 1 cause of blindness that comes with important emotional and economic strings attached," said Lassaline, a large animal ophthalmologist at the University of California, Davis. "In one retrospective study, approximately 15% of affected horses are euthanized, and by the time many horses are referred to a specialist, the horse's disease is al- ready at an advanced stage. Up to 25% of horses are already blind by the time they are referred. "In that same retrospective study, many horses with ERU already underwent a ca- reer change or had reduced activity, and about 50% tested positive for leptospi- rosis," a bacterial disease that can cause chronic uveitis, she added. To review, ERU is a painful immune- mediated form of uveitis— inflammation of the uveal tract, which comprises the iris, muscular ciliary body, and choroid. Chronic uveitis can cause permanent changes in the eye, including cataracts, glaucoma, and retinal detachment. "There are multiple causes for ERU, and despite the importance of this disease, ERU remains incurable," said Lassaline. In light of these facts, she encouraged practitioners to approach horses with painful eyes in a systematic and stan- dardized fashion to optimize chances of treatment success: 1. Recognize uveitis promptly. It is charac- terized by miosis (excessive constriction of the pupil); a painful, red, and cloudy eye; and low intraocular pressure. 2. Stain every eye. Corneal ulcers can also cause squinting, tearing, redness, and cloudiness. Staining the eye with a fluorescent dye can distinguish them from uveitis. 3. Always do a fundic exam to assess the structures in the back of the eye. "You can use a smartphone and an app that has a camera plus the light to per- form a fundic exam easily and thorough- ly," Lassaline said. For a veterinarian to diagnose ERU, the horse must have uveitis that has re- curred or is persistent. Veterinarians use a standardized grading scheme for ERU (e.g., on a scale of 1 to 5) to make an early diagnosis and assess treatment success. "In some ways, ERU is akin to lamini- tis, a recurrent and lifelong, life-altering condition," said Lassaline. For treatment, Lassaline recommended administering topical steroids, topical atropine to dilate the eye, and systemic non-steroidal anti-inflammatory drugs. Cyclosporine implants, which veterinari- ans place in the eye surgically, can reduce the frequency and severity of ERU flare- ups and can last for at least 48 months. Wrapping up, Lassaline reminded veterinarians that commercially available leptospirosis vaccines are not labeled to prevent or treat ERU. h e Visit TheHorse.com/AAEP2017 ■ Corneal Ulcer Cytology: How and Why, TheHorse.com/40215 Recognizing and Treating Corneal Stromal Abscesses in Horses When a horse has an "angry" eye, it's often due to a defect involving the surface, known as a corneal ulcer. Other times, however, a painful eye could reveal a deeper problem—a corneal stromal abscess—a condition equine ophthalmologists don't want veterinarians to forget about. Dennis Brooks, DVM, PhD, Dipl. ACVO, described deep stromal abscesses (DSAs). To briefly review: The cornea—the outer "window" that admits light to the eye—consists of several layers. On the outer surface, eight to 12 layers of epithelial tissue make up 15% of the total corneal thickness. Underneath lies a thicker layer called the stroma, followed by Descemet's membrane, which is a single layer of endothelium (thin skin cells, essentially) that covers the cornea's inner surface. "Abscesses of the stroma are usually not ulcerated," said Brooks, founder of the equine ophthalmology consulting firm BrooksEyes LLC. "Instead, horses typically present with pain- ful uveitis or inflammation of the uvea. The uvea provides nutrition to various parts of the eye and, if inflamed, can cause painful blindness." Brooks stated that DSAs can form in a number of ways. For example, they can develop secondary to a corneal ulcer when an infectious agent or foreign body becomes trapped in the stroma while the ulcer heals. Alternatively, a horse could develop a DSA after trauma to the eye that causes micropunctures, which allow bacteria or fungi to enter the stroma, even without creating a corneal ulcer. Veterinarians can recognize a stromal abscess in horses with a painful eye and a focal (single, distinct) yellow-white circular infiltrate in the corneal stroma, together with corneal edema (swelling). Sometimes, several abscesses can occur at the same time. "When examining the eye, if you see a fernlike frond or a collection of red blood vessels in a focal area, there is a reason they are there. To fully examine that eye you need to see past them," Brooks told conference attendees. "Simply apply some phenylephrine or epi- nephrine (to constrict blood vessels) to blanch them out to properly examine the patient to see if an abscess is behind the blood vessels." In terms of treatment, "always start with medical therapy," Brooks advised. "These corneal abscesses are very thick and not amenable to draining." Recommended treatment involves administering a combination of antimicrobials (includ- ing antifungals), anti-inflammatories, and pupil-dilating agents. Subpalpebral lavage sys- tems can help owners manage abscesses in the field; treatment might need to be applied four to six times daily for four to six weeks or longer. "These take weeks to heal," Brooks said. "During this process, we want the abscess to turn white, not orange. The goal is to have the uveitis and flare dissipate and the blood ves- sels disappear. If you see orange, refer the case immediately."—Stacey Oke, DVM, MSc