Equine recurrent uveitis, also called moon blindness, is the leading cause of vision loss in horses. Brian Gilger, DVM, MS, Dipl. ACVO, chief of the Ophthalmology service at North Carolina State University's College of Veterinary Medicine, covered the topic at the first AAEP Focus on Ophthalmology meeting in Raleigh, N.C., last month.

The condition typically affects a small percentage of the equine population (1-2%), but there is a much higher prevalence of this disease in Appaloosas (20-25%).

Equine recurrent uveitis (ERU) is currently classified in three main categories:

• Classic form which is the most common and involves episodes of active inflammation followed by latent low inflammatory periods;

• Insidious form involves a chronic, low-grade active inflammation that often leads to signs of ERU, and

• Posterior type which primarily affects the deeper areas (posterior) of the eye; the posterior form of ERU is the least common type in America but is more frequently seen in Europe.

A number of causative agents have been linked with the development of ERU, including leptospirosis, onchocerciasis, Streptococcus equi (strangles), brucellosis, toxoplasmosis, equine herpesvirus-1 and -2, equine viral arteritis, parainfluenza type-3, generalized septicemia, endotoxemia, neoplasia (cancer), tooth root abscesses, and even trauma