Hello Amber, Uveitis is a fairly common disease for the equine. Unfortunately, if it isn't treated in time, it can also cause loss of vision for the affected eye. Medically speaking, uveitis is an inflammation of the uvea, that is to say of the vascular part of the eye: the iris, the ciliary bodies and the choroid.
The origins of uveitis are varied. It may be associated with an eye wound, symptoms of systemic disease (inflammation attacking the entire body), but sometimes uveitis develops without apparent reasons. In this case, the uveitis bears the name "isolated uveitis". It is now accepted that the latter is the result of a dysimmune reaction (that is, a reaction caused by a dysfunction of the immune system).