Moon Blindness

Equine Moon Blindness

Equine Recurrent Uveitis (ERU) is the leading cause of blindness in horses. It is also often referred to as "Moon Blindness" as historically, the recurrent episodes were thought to coincide with phases of the moon. ERU is comprised of recurrent episodes of inflammation of the eye and specifically, the uveal tract of the eye. It is an immune-mediated disease process. Many things can trigger this disease and some horses may have a genetic predisposition to the disease. Appaloosas and European Warmbloods have a higher incidence of ERU than many other breeds of horses.

Common signs of ERU include squinting, increased tearing, small pupil size, and inflammation of the conjunctiva (soft tissue) of the eye. The disease is often very painful for horses. Many things have been associated with ERU as triggering events including bacteria, viruses, parasites, septicemia, abscesses, and severe trauma. Although we know ERU is an immune-mediated disease, the exact mechanism is still being researched.

The goal of treatment is to manage inflammation of the eye, decrease pain, and minimize recurrent episodes. This is often achieved through administration of steroids to the eye and systemic NSAIDs (non-steroidal anti-inflammatory drugs). Other medications that may be used are Atropine eye drops and antibiotics. Corneal ulcers (scratches to the cornea) can develop due to animals' aggressively rubbing their eyes because of pain. Corneal ulcers can complicate treatment as horses cannot receive topical ophthalmic steroids if eye ulcers are present. Because of this, it is important to have horses examined by a vet with each flare up of the disease, rather than just starting treatment. It is important not to place any medication into a horse's eye without a veterinary examination or authorization even if the medication was left over from a previous course of treatment. Instilling the wrong medication in the eye at the wrong time can potentially lead to blindness.

A newer treatment modality is an eye implant surgery performed by a specialist. This involves surgically placing a small sustained release medication device inside the eye. The device continuously releases medication directly inside the eye. Most horses respond favorably to this with decreased flare ups and increased comfort. Although this is not a good option for all horses with ERU, it can be a very useful treatment modality.

Treatment of the disease can be extensive in regards to both time and finances. Some horses may lose their vision despite aggressive treatment. Other horses can have well controlled disease and lead productive lives. At this time, there are

Equine Moon Blindness

No medications available to prevent disease occurrence. It is important to have your horse seen as soon as possible by a veterinarian if you have any concerns about the heath of your horse's eyes.


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