Equine vision

The equine eye is the third largest of any land mammal after the giraffe and the moose. Its visual abilities are directly related to the animal's behavior, for example, it is active both during the day and night, and it is a prey animal. Both the strengths and weaknesses of the horse's visual abilities should be taken into consideration when training the animal, as an understanding of the horse's eye can help to discover why the animal behaves the way it does in various situations.

The equine eye includes the eyeball and the surrounding muscles and structures around the eyeball, termed the adnexa.

The eyeball of the horse is not perfectly spherical, but rather is flattened anterior to posterior. However, research has found the horse does not have a ramped retina, as was once thought.

The wall of the eye is made up of three layers: the internal or nervous tunic, the vascular tunic, and the fibrous tunic.

Although usually dark brown, the iris may be a variety of colors, including blue, hazel, amber, and green. Blue eyes are not uncommon and are associated with white markings or patterns. The white spotting patterns most often linked to blue eyes are splashed white, frame overo, and sometimes sabino. In the case of horses with white markings, one or both eyes may be blue, or part-blue.

Homozygous cream dilutes, sometimes called double-dilutes, always have light blue eyes to match their pale, cream-colored coats.Heterozygous or single-dilute creams, such as palominos and buckskins, often have light brown eyes. The eyes of horses with the Champagne gene are typically greenish shades: aqua at birth, darkening to hazel with maturity.

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