Diagnosis and Management of Equine Uveitis, Including Equine Recurrent Uveitis

Introduction
Intraocular inflammation in the horse is a frequently encountered ophthalmic problem, commonly cited as the leading cause of blindness in this species. [Gilger et al. 2006; Gilger 2010; Gilger et al. 2010] Although equine recurrent uveitis (ERU, moon blindness, iridocyclitis, and periodic ophthalmia) has plagued the horse for thousands of years, there are still many unanswered questions pertaining to pathogenesis and etiology.

Most horses with ERU have recurrent bouts (episodes) of active intraocular inflammation of variable duration and severity, which are interrupted by “disease/symptome” free periods of apparent remission (quiescence). During these periods of quiescence there are no signs of active intraocular inflammation. Weeks, or even years may separate active bouts of inflammation. A key in managing uveitis in the horse is to accurately identify signs of intraocular inflammation, and determining if the disease process is primary (primary uveitis) or recurrent (ERU). Each horse that develops primary uveitis should be monitored for progression to ERU, which may not relapse for several years.

Many different etiologic agents have been associated with, or proven to be involved in, the development of primary or recurrent uveitis in the horse. While we will touch upon several of these agents in this presentation, we will mainly focus on the identification and interpretation of clinical findings essential for diagnosing uveitis, which ultimately results in improved disease management, appropriate and targeted treatment options, and improved long-term prognoses for many horses with primary or recurrent uveitis.  [...]