How they see
How does a horse see the world?
Almost 360°, with two blind spots
Two large eyes ride on the sides of a horse's long head, handing it a near-circular view of the world. That suits a grazing animal that must watch for predators with its nose in the grass. It sees blues and yellows clearly, though reds blend into the greenery, and the arrangement leaves two surprising blind spots: one directly in front of its nose, one straight behind its tail.
See through their eyes
Human ≈ 60 cpd (20/10)
How sharp is a horse's vision?
Its eyes resolve about 23 cycles per degree (20/26), while a human reaches around 60 cpd (20/10). Its field of view spans about 350°.
How does a horse see a human?
Its eyes resolve about 23 cycles per degree against your 60, so a face has to be roughly 3 times closer for it to pick out the detail you do. Your outline and your movement read clearly; your expression does not.
Colour comparison
How each colour shifts when seen through this animal's eyes, using the same colour model as the app. Tones a screen can't emit (such as ultraviolet) are shown as an approximation.
What colours can a horse see?
Sees blue and green well, red and green are confused. Yellows appear vivid.
Photoreceptors
Dichromat (2 cone types)
Cone peak sensitivities
- S (blue)428 nm
- M (green-yellow)539 nm
How does a horse see in the dark?
Tapetum lucidum; strong dim-light and motion vision.
How does a horse's vision compare to a human's?
At about 20/26, a horse has the sharpest acuity of any mammal here, though it still falls short of your 20/20. You take in three primary colours across 200 degrees; it settles for two, but spreads them across an almost complete 350.
What is special about a horse's vision?
- Almost 360° field
- Two blind spots: straight ahead & directly behind
- Good night vision
What the research shows
Carroll et al. (2001) measured the horse's photopigments electrophysiologically and placed its two cones at about 428 and 539 nm. That second value matters for the simulation: because the horse's longer cone sits close to the human middle-wave cone, the site models it with a protanope-like transform rather than the deuteranope-like one used for dogs and cats. Behavioural testing, including Hall et al. (2003), agrees that horses confuse red with green; the pigment pair puts the neutral point, where a wavelength looks colourless, near 480 nm. The eye itself is large, rod-rich and backed by a tapetum, and it adapts slowly between light and dark.
Acuity was measured behaviourally by Timney & Keil (1992), whose best result was about 23.3 cpd; that is the basis for the 23 cpd and 20/26 shown here. Estimates from retinal anatomy come out lower, around 16.5 cpd, so the displayed value sits at the sharp end of the evidence. Detail is also not spread evenly. Instead of a fovea, the horse has a horizontal visual streak, a band of dense retinal cells, so its sharpest vision lies along a line rather than at a point, and binocular overlap in front is about 55–65 degrees. A filter applied evenly to a whole frame cannot reproduce that band, and a single image cannot show slow adaptation as light changes.
Guides: Are animals colour blind? · Which animal has the best eyesight? · All guides
Scientific sources
- Carroll, Murphy, Neitz et al. (2001)
- Hall et al. (2003)
- Timney & Keil (1992)
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