Acute uveitis: Circumlimbal corneal edema and neovascularization, severe miosis, blepharospasm and lacrimation.
or slit lamp shows deterioration of numerous ocular structures that is progressive over time. Pupils may be slightly miotic. Other subtle signs include corneal haze, slight aqueous flare, muddy iris color, iris rim and/or corpora nigrans atrophy, cataract, low-grade vitreous haze and chorioretinal scarring. Insidious uveitis is most often seen in Appaloosas, draft horses and European warmbloods. ****Miosis is a hallmark of acute ERU. Miosis is a component of persistent insidious uveitis as well, but usually to a milder degree. B. Classification by region of ocular involvement 1. Panuveitis: Cases where the entire uveal tract is inflamed. Most cases of ERU and insidious uveitis involve a panuveitis. 2. Posterior uveitis: Inflammation is predominantly observable in the posterior segment (vitreous, retina and optic nerve). Most often seen in draft horses and European warmbloods. C . . Classification by stage of disease at time of examination: 1. Active, or acute cases are horses suffering from a flareup of classic uveitis. Signs of an acute bout vary but include pain, lacrimation, photophobia, chemosis, conjunctival hyperemia, corneal edema, corneal vascularization, dotlike keratic precipitates on the corneal endothelium, aqueous flare, hyphema or hypopyon, miosis, vitritis, and ocular hypotension (pressure of 10-12 mm Hg). 2. Quiescent cases are horses in a “calm” time of their cycle of repeat inflammation. Slit lamp examination will show subtle flare in the anterior chamber, indicating low grade but persistent inflammation. Ocular examination may reveal “footprints” of previous disease including chronic corneal edema, iris atrophy, iris color change, synechiae
(adherence of the iris to the lens or cornea), pigment rests on the anterior lens capsule, cataract, densities or haze in the vitreous, or scarring around the optic disc. Chorioretinal scarring from previous inflammatory episodes is evidenced by either a “bullet hole” pattern, where numerous tiny, pale ring-shaped scars with hyperpigmentated centers occur in a geographic pattern in the peripapillary region, or as alar scarring, where islands of retinal depigmentation flank the optic disc in a pattern resembling butterfly wings. 3. End-stage cases are horses with longstanding, chronic ERU that have undergone severe degeneration. The affected eye(s) may show extensive corneal scarring, circumferential synechiae, dense cataract, lens luxation or subluxation, secondary glaucoma, retinal detachment or phthisis bulbi. End-stage uveitis is associated with vision loss. Diagnosis of uveitis is simplified by understanding that a horse may present anywhere along the spectrum from acute to end stage, and as either a recurrent or insidious case. Horses that present with three or more signs of intraocular inflammation and a history that is suggestive of either recurrent disease or breed-associated insidious disease can be given a presumptive diagnosis of ERU or persistent uveitis. Examination of these horses may reveal some signs reflecting acute or recent inflammation and other signs representing chronic ocular scars from previous episodes. Inflammation is always present on a cellular basis in both quiescent and insidious cases, so sequential examination may discover progressive ocular deterioration in horses that have seemed “normal” to their owners. NOTE: Care must be taken to assure that there is not another primary problem in any eye that is demonstrating intraocular inflammation. The cornea must be examined closely for signs of corneal ulcer, stromal abscess, foreign body, neoplasia and immune mediated or idiopathic keratitis. The globe should be examined for neoplasia. Ruling out concurrent ocular disease
Chronic uveitis: Corneal edema, pupil iris atrophy, luxated lens with dense cataract.
12 The Practitioner Issue 4 • 2016