Moon Eye in Horses

Moon eye is actually a name given to the disease equine recurrent uveitis in horses. The reasons for the name are multiple. During advanced stages of the illness, the eye becomes opaque and covered with a white film, giving the appearance of a "moon" color and shape. In addition, the pain caused by sunlight to the eye will often have the horse seeking cover unless it is dark. The illness itself has nothing to do with the moon.

Moon eye is not completely understood, but according to the Merck Veterinary manual, most veterinarians believe it is an attack from the body's immune system on itself, much as with rheumatoid arthritis and other autoimmune disorders. An injury that causes the immune system to overreact can cause the condition.

  1. Features

    • The features of the disease are inflamed tissues surrounding and inside the eyeball, causing acute irritation, pain, sensitivity to light, tearing, the formation of scar tissue on and around the cornea, and eventual blindness. The eye will appear infected with no apparent cause, and the horse will show discomfort and try and protect the eye from light and other irritants. Eventually, the scarring causes a bluish cast, or "moon eye" on the eyeball, blocking off the vision of the eye itself.

    Significance

    • The main effect of moon eye is that the horse will eventually go blind in the eye, and possibly both eyes, if the condition is not treated. During the period that the eye is losing vision, the horse will suffer from pain, swelling and irritation, and in some cases will rub and damage the eyeball in an attempt to alleviate the pain. This effects the overall ability of the horse and its functionality, impairing the use of the animal.

    Time Frame

    • Moon eye often takes a long time to completely blind the eye. The disease, if left untreated, may take months to severely affect the vision of the eye. If the horse receives daily treatment, blindness may never occur. The time frame of the progress of the disease depends on the severity of the case and the type of treatment given. Professional veterinary help is recommended to determine the severity of the illness if moon eye is suspected.

    Treatment

    • The normal treatment for moon eye is the administration of corticosteroids and anti-inflammatory medications. The main effect of these drugs is to lower the body's immune response and prevent swelling and inflammation of the eye tissues. In severe cases, daily treatment is needed. In more moderate cases, treatment is only needed during flare-ups of the disease.

    Warning

    • It is important to note that the disease can spread to both eyes. While the affected eye may be the first to show symptoms, the response to the disease may travel through the body fluids to the other eye, which can then lead to blindness in both eyes. In some cases of aggressive moon eye, it may be necessary to remove the eye that is showing severe degeneration, to prevent the other eye from also becoming affected.