- Question #1 – First of all, how does an eye work?
- Question #2 – What is the difference between our vision and the horse’s vision?
- Question #3 – Can the horse really see behind itself?
- Question #4 – And how does it perceive colors?
- Question #5 – Can the horse see well at night?
- Question #6 – So, how to take this into account when riding ?
“My horse refused to jump another red obstacle… When I tell you he doesn’t like that color! It scares him! And he keeps seeing ghosts in the woods when I hack, I think he needs glasses!” Well, how do horses see? What if I tell you that horses can’t see red and that they can see in the dark as well as cats? Let’s take a look at the horse’s vision.
Question #1 – First of all, how does an eye work?
Let’s start with a little bit of anatomy.
The eye of the horse is very similar to the eye of the human being in its structure.
The cornea and the eye lens work like two optical lenses that will collect the light coming from outside, concentrate it and finally form the image on the retina. The retina is actually lined with small receptors that are sensitive to different types of light. The iris, the colored part of the eye, regulates the amount of light sent to the receptors by contracting and relaxing. At this point, the image is upside down. It is sent to the brain by the optic nerve and it is the brain itself that turns the image right side up.
Question #2 – What is the difference between our vision and the horse’s vision?
The difference between the vision of the man and the horse is twofold. The first is the shape of the pupil which is elongated and horizontal in the horse. For example, it is clearly vertical in cats and round in humans. This is what allows the horse to have a panoramic vision.
The second is the light receptors. There are several types: rods and cones. The rods make it possible to capture an image even if there is little light. For example, they are the ones that allow us to see in a dimly lit room. But in this case, no color, everything is gray! If we see colour it is thanks to the cones. There are three types of cones: some capture red light, others blue light and the last ones green light. And it is by associating the results of each type of cone that we see all the colours of our spectrum. The peculiarity of the horse is that the distribution of the types of receptors is not the same: the horse has no red cones (it has dichromatic vision) and more rods than humans.
Question #3 – Can the horse really see behind itself?
Almost yes! The fact that it has his eyes on the side of its head allows him to see much better than we can on the sides and “behind” itself.
On the right and left sides the horse sees with only one eye, whereas in front of him it sees with both eyes. However, the perception of depth is only possible in the binocular vision areas. Experiment, close one eye and try to catch an object in front of you. Not impossible, but much more complicated than with both eyes open. You have “lost” 3D vision. The horse can only see in 3D in a small area of about 60-65° in front of itself.
In fact, its blind spots are under his body, in front of its nose-line (turn him into a unicorn, it won’t even see it …), behind its croup and on an area of about 1.20m in front of its forelegs (depending on the position of his head). This means that in the last stride before an obstacle, the horse can no longer see what it has to jump!
Also, the horse has a “low” and horizontal vision, it doesn’t see above itself, whereas we see a little above eye level. In fact, it sees a bit like when you wear a cap. That’s why it raises its head strongly when it hears or sees something (ghosts)!
Question #4 – And how does it perceive colors?
Well the horse has a dichromatic vision as I explained above. They don’t perceive red.
It’s a form of color blindness, actually. It disrupts all color perception. The horse will see everything in “pastel” version and in shades of brown, yellow, blue and grey. In humans this is what we would call “protanopia”. Horses would see something like this:
Question #5 – Can the horse see well at night?
Yes! The horse does indeed have more rods than humans. So that implies that it can see much better than us at night, almost as well as cats even. However, it has a big disadvantage compared to cats and us, which is that it adapts much less quickly to changes in light. Indeed, in their natural state these changes are slow since they are due to the sun going down, so it takes 20 to 30 minutes for the horse to adapt to the dark. So, when you try to get the horse into a van or when you get him into a dark stall, it will only see a black hole! (Not cool)
Question #6 – So, how to take this into account when riding ?
All this has, of course, consequences when riding, of which we must be aware.
Indeed, their horizontal and “low” field of vision explains why the horse raises its head when it is about to jump. Thus, a horse that is on the hand will almost only see the ground, and if falsely bent then it will only see its forelegs. This makes it difficult for the horse to jump. There is even a risk that he will cross the obstacle.
For the little story, I tried to make a video by jumping a small obstacle once in “normal” position and once with a closed attitude until the end, I never succeeded… I let you test, you’ll see 😉
Moreover, this is why we consider that a position on the hand favors the submission of the horse since it has to rely on its rider to see in its place.
For riders with one-eyed horses, knowing that monocular vision disturbs 3D vision is information to be taken into account at all costs, because on the one hand the horse will have more difficulty estimating its distance to the obstacle, and when approaching an obstacle on the exit of a curve on the side of its blindness, it may only see the obstacle at the last moment! You will notice moreover that jumps with on this hand there will be less precise.
I hope that thanks to this article you will see more clearly (little play on words) the way the horse perceives the world, and that it will help you to better anticipate its needs and reactions.
I want to know more about the horse’s senses –> The ghosts your horse sees are real
See you soon for a next article
Alice Martinez & Camille Saute
R&D engineers at Equisense
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