Eyesight (vision) is the most important sense for your horse.
For a prey animal, the constant, vigilant monitoring of the surrounding environment is crucial for survival.
Horses are very sensitive to motion and will usually react by trying to get as far away as possible from whatever suddenly entered their field of vision.
If the movement is further off, a preparation for flight (raising the head, tensing the body, defecating etc.) is a typical response.
Horses, like all equines, are particularly sensitive to movement in the periphery
Predators usually stalk a herd of prey animals in tall grass or shrubbery off the edge of the herd, circling the group and looking for a suitable target.
When you’re training and working with your horse, you should always take this sensitivity to sudden and unexpected motion into consideration.
The visual abilities of your horse are directly related to her behaviour as a prey animal. Understanding the strengths and weaknesses of her visual abilities will help you to make the most of your training.
A horse can be trained to deal with new and unexpected situations if they’re systematically and continually trained to control their own instinctive reaction to it, but it takes consistent work from you.
Your horse’s eyes
Horses have the largest eyes of all the land mammals and they see well both in daylight and in low-light conditions.
Your horse doesn’t adjust well to sudden changes in lighting conditions, so when you’re taking her from a sunny day outside into a barn or stable, you need to be aware of that her eyes adapt slowly to the darker conditions inside.
This is also a critical factor to take into consideration when you’re loading your horse into a trailer, as she needs to be given enough time to adjust to the darker interior.
If you demand that she load from bright sunlight quickly into a trailer, you may get a lot of resistance.
Try taking it more slowly, or placing the trailer in the shade of a building to help stagger the change in light.
Your horse’s eyes are positioned and shaped so that she sees best when her head is down
When your horse wants to focus on something and study it more closely, she will raise and lower her head in order to adjust the object in her field of vision.
This is another reason why you shouldn’t demand that your horse keep her head up when encountering new things or moving between different lighting conditions. She will be twice as scared of something she cannot clearly make out.
How do horses see colour?
Horses have dichromatic, or two-coloured, vision (as compared to the three-colour, or trichromatic, vision of humans).
They can see colour but have difficulty distinguishing between some colours.
Your horse can distinguish between blues and yellows, but reds and greens blend together. This should always be taken into consideration when building obstacles for horses to jump.
The red that makes the jump stand out like sore thumb to us (below) blends into the background for the horse, making it more difficult to see.
I don’t know anything about the design process for obstacles, but I imagine that the designs are made more for the delight of the sponsors than they are for the safety of the horses.
Considering that it is always the horse doing the heavy lifting whenever we ride, my opinion is that we should prioritise the safety and wellbeing of our horses and design the environments we put them in accordingly.
After all, it can be very costly to treat an injured horse, and in a worst-case scenario, the injured horse will have to be put down.
Your horse has something called binocular vision
Considering your horse’s binocular vision is important when you’re working with her.
Riding with the head perpendicular to the ground, “on the bit”, affects her binocular vision by turning it down towards the ground.
Your horse will focus on objects closer to the feet and can be more easily startled by things moving in her peripheral vision.
To focus on objects, your horse will raise her head.
In showjumping, this is particularly evident when you see that a horse is allowed to raise the head some steps before the jump in order to properly assess the obstacle as well as the right take-off spots.
How the binocular vision of your horse is affected by the angle of the head
Your horse’s field of vision is over 360 degrees, which means that horses have one blind spot in front of the face and one directly behind the head (this one extends over the back and behind the tail when the horse is standing with the head straight forward).
Blind spots are depicted in dark blue.
The right and left monocular fields (green) cover about 285 degrees combined and the binocular vision (orange) is about 65 degrees.
Monocular vision means that the left and right eye work separately and this widens the field of vision as compared to binocular vision, where both eyes are used together.
Monocular vision has poorer depth perception than binocular vision
However, the wide field of vision allows for sensitive observation of movement even in the periphery (in orange).
Prey animals such as horses, cows and goats benefit from a large field of vision because they can monitor a large area around themselves and keep a lookout for predators.
Among others eagles, owls, humans and wolves have binocular vision that helps in-depth perception, assessment of distances and focusing on single objects.
Since your horse has a very wide viewing area but only a narrow field of vision that is acute, she will always try to place her body within this visual field where she can see clearly.
You should also consider, that the lens in the eye of your horse begins to deteriorate after age 10 (if no injury has occurred before) and you should be aware of this and anticipate that your ageing horse may need more care and assistance in the future.
How to consider your horse’s unique vision when training and handling her
The surface of your horses skin is particularly sensitive when it comes to motion detection. When an unexpected movment occurs in the perihperal vision, your horse’s first instinct isn’t to turn around.
She will either quickly relocate to a safe distance (bolt) before turning and looking back. This may or may not be accompanied by a swift kick intended to immobilise the threat while your horse gets to safer ground.
This is why standing behind your horse (blind spot) or walking up to a horse and using the rump or hindquarters as the first point of touch, is not a good idea.
Earmuffs can help with calming a skittish horse
The wind and things that are rattled by the wind, will not carry their sounds to your horse’s ears as directly as without the earmuffs.
In general, the horse is a large flight animal, her whole body fine-tuned to detect even the smallest threat, so it is advisable to always approach your horse in a calm and assertive manner, well within her field of vision, and always know that she may respond abruptly.
How to make the most of your horse’s unique vision
Horses can and do explore the world around them, the animals and people they interact with, by using their eyes.
However, since the sharpness of their vision is limited, they rely heavily on their other senses to interpret the world and events around them.
For a horse to run at full speed, she cannot put all her trust in her sense of sight only.
When you ride your horse, she relies on you to help her navigate the environment and the obstacles in it.
For this reason you should develop your relationship and build a strong bond, so that you can help her reach her full potential.