Horses with blue eyes are an uncommon sight. Due to their uniqueness they have been regarded as a mysterious, and at times suspicious, characteristic, with many tales spun regarding their origins and significance.
Blue eyes are created by pigmentation, or rather, the lack thereof. Melanin present in the iris of regular horses is what creates the brown colour. Due to their uncommon genetic make up, blue eyed horses lack melanin in their eye, causing the lighter, un-pigmented shade.
In some cases horses can have mismatching eyes, with one brown and the other blue. A horse may also have parti-coloured irises, with a striking mixture of blue and brown present. These are very rare, with the American Quarter Horse Association only registering a small handful each year.
Double-dilutes, such as cremellos and perlinos, always have light blue eyes due to the presence of the cream gene. The dilute genes act as a ‘whitewash’ over the underlying coat colour. A dark base coat is bleached to a pale cream and the dark brown iris faded to pale blue.
Blue eyes can appear in almost all horse breeds, though American Paints, Appaloosas, Quarter Horses, Gypsy Cobs, Miniatures and Tennessee Walking Horses are the most likely bearers. However, the lighter-toned eyes have suddenly appeared in normally brown-eyed breeds such as Arabians and Thoroughbreds.
Over the years, many different terms for blue eyes have developed. Some common ones include ‘glass eye’, ‘moon eye’, ‘China eye’, ‘wall eye’ or ‘night eye’.
Folklore is full of stories of blue-eyed horses, some saying the marker a positive sign, others as an indicator of a dangerous animal. Old Wives Tales tell of blue eyes being a sure sign of a spooky temperament and weakness. Other legends tell of fair-eyed horses as holders of great wisdom.
The common belief of blue-eyed horses being prone to poor eyesight and blindness however is distinctly untrue. Just as people with blue eyes can see as well as people with brown eyes in humans, so too is horse vision unaffected by iris coloration.
The idea might be partially due to incorrect association a condition called Corneal Edema. If a horse accidentally bumps its face or the eye is otherwise irritated, the surface of the cornea can be damaged. As a result, the eye can take on a bluish hue and can cause vision impairment. However this is very different in appearance and nature to horses born with blue irises. Edema is painful and should be treated immediately.