Horses have better night vision than humans, so we get used to horses leading by moonlight. That is, unless they suffer from Night Blindness or more descriptive Congenital Stationary Night Blindness (CSNB). CSNB is an inherited disease primarily of leopard spotted Appaloosas. Though the genetics are different, CSNB is infrequently seen in Tennessee Walking Horses, Paso Finos, Thoroughbreds, and some other European breeds. This article describes the causes, mode of inheritance, diagnosis, management, and prognosis of this eye condition of horses.

The degree of blindness varies from case to case. In its mildest form, the horse may exhibit mild disorientation and apprehension at dusk or dark, occasionally running into objects. At its most severe, horses are blind when the lighting is poor, with increased signs of fear and running into stationary objects. Some severely affected horses are also apprehensive in bright light. Foals may stargaze in their stall at night. Occasionally there is a strabismus (deviation in the direction the eye looks) and nystagmus (regular eye twitch). Noteworthy is that the degree of night blindness is non-progressive so will not worsen over time, though adverse events may make a horse more apprehensive.

Horses with two copies of LP were recently shown to be at an elevated risk for equine recurrent uveitis (ERU) which is a progressive condition and the leading cause of blindness in horses. The cause is uncertain but being researched.