Equine Recurrent Uveitis (ERU), the most common cause of blindness in horses and mules, is an immune-mediated disease. ERU is also called moon blindness because historically its recurrence was thought to be related with the phases of the moon. It is believed to have many different causes, such as bacterial, parasitic, trauma, viral, or immune disorders.

Information for the Horse Owner. This pamphlet has been compiled by a horse owner for other horse owners as a source of information on equine recurrent uveitis. The impetus for this project came from owners across the country seeking information on this disease and pooling their knowledge to help each other.

In days gone by the condition use to be termed "Moon Blindness"; quoting from Modern Practical Farriery, published in 1882; "It was a superstition that the periodical attacks were influenced by the monthly return of the moon."

Known as the leading cause of blindness in horses, equine recurrent uveitis (ERU) is characterized by several attacks of intra-ocular inflammation alternated with variable periods of clinical quiescence. Authors: Antonio Cezar de Oliveira Dearo, Mirian Siliane Batista de Souza.