Equine Recurrent Uveitis (ERU), an immune-mediated disease, is one of the most common causes of blindness in horses. ERU is commonly referred to as “moon blindness” and is believed to have several possible causes including bacteria, parasites, viruses, trauma and immune system disorders. ERU is characterized by increasingly frequent bouts of irritation and inflammation in the eye (uveitis).  

Clinical signs of corneal ulceration include squinting (or holding eye closed), rubbing, tearing, redness or swelling of the conjunctiva (the membrane that covers the white part of the eye and lines the inside of the eyelids), and cloudiness of the cornea. If your horse exhibits any of these signs, contact your veterinarian immediately. All corneal ulcers in the horse are considered an emergency.