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I noticed all the horses in our pasture staring in the same direction. The object of their attention was a feral red hog. Their concern was evident, which led me to wonder about their vision, and more specifically, if horses are color-blind”?
Horses aren’t color blind, but they don’t see all the colors humans can. A horse sees blue and green and variations of these colors, but they don’t distinguish red. Horses have enormous eyes, which allows them to see excellent at night.
Many people believe that horses with their large eyes have better color perception than humans. But as I learned, there is a lot more to color recognition and visual acuity than the size of a horse’s eyes.
How horses see colors.
For centuries scientists and horse riders believed that horses were color blind. However, as technology advanced, we’ve learned that horses can see color, just not the same as we do.
Testing of horses’ visions confirmed they can differentiate some colors. Researchers were able to measure the strength of the response of the pony’s eye. The reaction of the pony’s eyes allowed them to determine which colors they could see.
The testing confirmed that horses have two types of cones in their eyes, classifying their vision as “dichromatic” color vision. Humans are considered to have a “trichromic” vision or three cones. The test also confirmed for the first time what colors a horse can and cannot see.
Horses see spectrums of blue and green colors.
Horses can blue, and green colors of the spectrum and their hues, humans with normal vision see four primary colors–blue, green, yellow, and red–along with approximately 100 blends and tones.
A double-blind study using colored buckets tested a quarterhorse mare’s color vision. The test confirmed the mare could discriminate between blue and gray, and red, but not between gray and green.
Horses can tell the difference between blue and red.
Even though a horse can’t distinguish red, it can tell the difference between it and blue. Because a horse doesn’t distinguish red doesn’t mean the horses don’t see anything red. Instead, they don’t see red in specific zones with other colors.
Humans diagnosed as “color-blind” actually have a dichromatic vision and see a color palette similar to a horse. The main difference between dichromat and trichromat vision is that anyone with dichromatic vision will not see intermediate hues.
In horse competitions, the lack of visual acuity is taken into consideration when designing courses. Often jumps and other obstacles will be painted colors easily seen by the competing horses. Horses aren’t color blind, but they don’t see colors the way we do.
Horses’ don’t see colors the same as humans?
Horse’s color perception is less than humans. For many years horses were believed color blind, but we now know this is not the case. But, horses’ color vision is much weaker than humans. Why are we confident that horses have limited color vision?
A team of scientists conducted detailed testing on six ponies and published their results in the Journal of Vision. These scientists used the latest technology to monitor the pony’s reaction to colors.
How Good Can A Horses See At Night?
Horses move around a lot at night, and they seem to be as comfortable at night as during the day. While watching them one night, I started wondering about their night vision.
Horses have large eyes and a layer inside their eye that reflects light to the retina, these two characteristics give them the ability to see much better than humans at night. Horses have exceptional night vision.
The strangest feature of the horse’s eye is its huge size-twice as big as the human eye. It is one of the largest in the entire animal kingdom and amazingly is bigger than the elephant or the whale’s eye. It also possesses a unique light-intensify device.
This device is called the tapetum lucidum. The tapetum lucidum is a layer that reflects light onto the retina and makes the horse much better than its rider at seeing in dim light. It also gives the horse’s eye a ‘glow” similar to the shine of a cat’s eyes at night.
Horses are nocturnal animals.
Together these two facts--huge eye with light-reflecting layer-lead to an inescapable conclusion: The horse is a nocturnal animal! To anyone who has studied zebras in the wild, this will come as no great surprise.
Herds of zebras are intensely active in very dim light at dawn and dusk and can see much better than human beings in those conditions. We are so used to thinking of the domestic horse as a daytime steed that we have overlooked this critical aspect of its natural lifestyle.
Riders who ride and jump with their horses at night confess it is a nerve-racking experience for them; however, their equine partner takes it all in stride.
The fact that the horse is naturally active by night does not mean that it is typically inactive by day. It is even more engaged by day and is, in fact, both strongly diurnal and nocturnal.
Horses are always scanning the horizon for predators.
Throughout the long waking phases of the day and night, the horse’s eye is forever scanning the horizon on the lookout for possible killers. And the animals’ vision is structured so that it is super sensitive to the tiniest movements in the distance.
Even today, after living its whole life in an utterly lion-free world, a domestic horse can still be panicked by the sudden fluttering of a sheet of paper in the wind, somewhere at the edge of its range of vision. The old fears die hard.
What is the horses’ range of vision?
Watching racehorses run with quarter cup blinkers makes me curious about the animal’s peripheral vision.
A horse can see about 340 of the 360 degrees around it, with only two small blind spots, just in front and immediately behind its body. For this reason, it is crucial not to approach a horse, even an ordinarily docile one, from those angles.
Its sudden realization that someone has come close to it may startle it badly when an invisible hand pats or strokes it. Always speak to a horse when approaching and walk towards it slightly to one side, where it can see you.
Because the horse’s eyes are set on either side of its head, it does not usually see objects in-depth, with binocular vision. It sees them flat, as we do if we shut one eye. It also sees less detail than we do but is much more sensitive to movement than we are.
Horses can’t focus their vision on up-close objects.
Despite this predominantly lateral vision, the horse is capable of a narrow band of three-dimensional vision if it directs its gaze immediately forward. This vision only works at a distance of more than six feet in front of the animal’s head because of its long muzzle.
This is a sobering thought for any jump-jockey. It means that every time he urges his steed over another large fence, the animal is jumping blind.
As the horse approaches the jump, he can see it clearly with both eyes. But at the last moment, the jump disappears from view, blocked by the obstruction of the horse’s own head.
To use an airport analogy, it is as though it is jumping by instruments. It sees the jump coming and then memorizes its position as it sails blindly through the air.
Showjumping horses lose sight of the fence at the last second.
This visual flaw is the reason why a show-jumping horse sometimes crashes into a fence as if it had not seen it. What happens on such occasions is that something else has momentarily caught the animals’ eye and distracted it, leaving it with no defense against the rapidly approaching obstacle.
An examination of jumping horses reveals they frequently turn their head slightly right before a jump to get at least a one-eyed view of the barrier they are approaching. A slight turning of his head doesn’t cause harm, so long as the horse doesn’t twist his head too soon.
If the jumper turned his head early, he would lose depth information and not be able to judge the distance of the jump ahead. This information is needed to calculate his leap.
When a horse is narrowing its pupils in intense light, there is a striking difference from the human reaction. In us, the circular pupil becomes smaller, ending up as a tiny black dot. The pupil narrows to a slit in horses, but not a vertical slit like a cat’s.
Instead, it shrinks to a horizontal slit. The horizontal slit is a unique adaptation to the horse’s need to keep a broad horizon in view at all times. The pupils may be smaller in the glare, but the vast range of vision remains unimpaired.
Because a horse has a rear blind spot, try to avoid approaching it from behind.
How far can a horse see?
How far a horse can see is challenging to answer. I couldn’t find reliable scientific testing that confirmed the distance horses could see. But I did read a story you may find interesting.
In a contest between rival Arab riders, they proved a horse could identify its owner from other men at distances of over a quarter of a mile. How they did this remains in doubt, but the horse likely identified natural movements rather than details about their rider.
But in whatever way they managed it, it underlines the fact that the eye of a horse is a truly remarkable organ. A research team exposed horses to two sets of doors, stripes, and solids in a more recent and objective testing situation.
Behind the striped doors, they hid treats. To receive a reward, the horse had to choose the multicolored door over the solid colored door.
The researcher reduced the stripes’ thickness on the doors until the horses could no longer tell the difference between a door with lines or one without stripes.
From this test, they determined a horse can see 20/30; for comparison, a cat sees at 20/75, rats at 20/300, and a normal humans vision is 20/20.
Anatomy of a horses eyeball
A horses’ eyeball is flat at the front and back and doesn’t have a “ramped retina.” A ramped retina is a term used to describe retinas shaped in a way that creates different distances from the lens within the eye.
Researchers thought the ramped retina was the reason horses moved their heads up and down so often. The theory was that by shifting their heads, a horse focused his vision, similar to the way a human would see through bifocals.
However, modern science has proved this theory to be incorrect. We now believe a horse lifts his head for better distance vision because binocular overlap occurs with the nose lifted. A horses eyewall has three layers:
The retina is also called the nervous tunic. The retina includes cones and is light sensitive, and provides the horse’s capability to see colors. The retina also houses rod cells that catch light and dark differences and includes night vision capabilities.
Only two-thirds of a horse’s eye can receive light; because of this, the horses’ eye has a blind spot.
The uvea or vascular tunic includes the choroid, ciliary body, and iris. The pigment is located in the choroid and reflects light onto the retina.
The iris is between the cornea and the lens and gives the eye its colors. The iris also allows light to pass through the pupil.
The fibrous tunic protects the horse’s eye. It is made up of the white of the eye (sclera) and the cornea. The cornea is the clear covering on the front of the eye.
The lens is behind the iris; it changes shape to focus light on the retina. The horse can contract and relax small muscles to adjust the lens. The lens thickens to focus on close objects when contracted. When the muscles are relaxed, the lens becomes thinner to see a distant object more clearly.
The nictitating membrane acts as a windshield wiper and is often called a third-eyelid; it is common in most animals. A horse’s third-lid sits in the corner of the eye and will wipe across the eyeball to remove irritations.
It is essential to keep this clean, and it is susceptible to developing cancer. You should have an eye exam for your horse at least once a year, and you should wipe away any excess from in the horse’s eyes with a soft cloth.
The Corpora nigra purpose is uncertain. The corpora nigra is a group of knobs that sit on top of the iris. It could be a sunshade for the horse’s eyes; no one knows for sure. It is a common feature of a horse’s eye that goes unnoticed by most equestrians.
When it is noticed, some believe their horses’ eye has erupted and called their veterinarian. I guess it is better to be safe than sorry.
Equine eye colors
What is the most common color of horses’ eyes?
Brown eyes are the most common in horses. The iris of a horse’s eye is usually dark brown to black but could be various other colors, including blue, hazel, amber, and green. The most common color is brown, and the rarest is green.
Regardless of the color of your horse’s eyes, their vision should be the same. Breeds that are most likely to have blue eyes are Appaloosas, Paints, and Pintos.
Amber and hazel eyes in horses are caused by a dilution of the champagne gene color and are most often seen in light-colored horses like palominos or buckskins. The Paso Fino breed has actual yellow eyes.
Over the years, this color of eyes has been called “Tiger” or “Goat” eyes. Green-eyed horses are scarce and only occur in either pearl or cream-colored horses.
What are some common equine eye problems?
Common problems with horses’ eyes include abrasions, corneal ulcers, keratitis, conjunctivitis, uveitis, habronema, and keratoconjunctivitis sicca.
A corneal abrasion could be a simple scratch or a more complicated infection. These are usually superficial and will heal on their own within 3 to 7 days. Horses are highly susceptible to developing corneal diseases.
A corneal ulcer is a loss of corneal tissue, usually caused by an abrasion that has inflamed the cornea. This condition can be excruciating.
Keratitis is a condition in which the horse eye’s cornea becomes inflamed. Keratitis results in pain and some loss of vision.
Conjunctivitis is a condition considered “pink eye” in humans. It occurs when the white of the eye turns reddish. It can be painful and is itchy.
Uveitis is the inflammation or swelling of the middle layer of the eye that contains pigmentation. It is the outer fibrous layer. Uveitis is an emergency for the horse, and you must try to control the inflammation immediately.
It is also referred to as moon blindness and is the most common cause of blindness in horses. Also called Spontaneous Equine Recurrent Uveitis and about 10-15% of the equine population will suffer from this eye disease during their lifetime.
Habronema is a nasty disease caused by maggots depositing larvae from feces into open sores and horses’ mucous membranes. It may develop in numerous locations on the horse, but the eye is the main area affected.
Other areas included the moist portion of the lips, penis area, or any site with an open lesion. It is a summer disease and will reoccur annually. Symptoms may include tumors with a yellow granular seepage.
Keratoconjunctivitis sicca is the scientific term used to describe “dry eye” syndrome in horses. A fracture of a facial bone could damage a nerve and disrupt tear production.
The infection could also be a cause of this syndrome. Be sure to have your horse checked by a veterinarian if you suspect he has “dry eye” syndrome.
Serious eye problems of your horse can be prevented by early detection. When you groom your horse, check his eyes, and wipe away any fluid.
If you think he has a condition that warrants calling your veterinarian, then schedule your horse an examination. Taking these steps could save you a lot of heartache and money.
Contact a vet if your horse sustains an eye injury.
When a horse sustains an injury to his eyes, it requires that you seek immediate veterinary care. Eye disease left untreated can lead to blindness. Signs to watch for include swelling, redness, and abnormal discharge.
When you see any of these signs, contact your veterinarian. And follow these instructions:
- Cover the horses’ face with a fly mask if you have one available. If you don’t have a fly mask, do whatever is necessary to prevent the horse from rubbing his eye.
- Next, place the horse in a clean environment to avoid exposure to substances that could cause further damage. (Click the link to check prices for a Fly Mask with Ears on Amazon)
- Put your horse in a quiet, dark stall; light could irritate his eye.
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- To learn why some racehorses bleed from their nose, click here.
- To read about what we can learn from a horse’s teeth click here.
- To read about the sounds horses make click this link.