Equine Night Blindness

Night blindness, also called congenial stationary night blindness, is a condition which affects horses and prevents them from seeing in the dark. The condition primarily affects Appaloosas, though according to Dennis E. Brooks, DVM, it has also been reported in thoroughbreds, standardbreds and paso finos.

  1. Symptoms

    • According to Dennis E. Brooks, DVM, horses with night blindness cannot see in the dark, though they can generally see quite normally in daylight. The visual impairment at night is often reflected in affected horses' behavior, as they can be uneasy and unpredictable in the dark. Brooks states that in some cases, horses affected by night blindness have developed difficulty seeing during the day, as well.

    Diagnosis

    • Diagnosing night blindness is made by using an electroretinogram. According to Lynne Sandmeyer, DVM, the horses are kept in the dark for a number of minutes, and then exposed to flashes of light. The electroretinogram measures the retina's electrical activity when exposed to these flashes of light, which identifies whether a problem is present with the eye's ability to register the retina's signals.

    After the Diagnosis

    • Although there is no cure for night blindness, the disease is manageable with some adaptations on the horse owner's part. According to Sandmeyer, the horse should not be ridden or worked in the dark, and any hazards should be removed from their paddock such as branches or holes. Sandmeyer states that night blind horses often still know the boundaries of their fields in the dark.