May 17, 2022 
The other morning after having washed my face I reached for my glasses and wondered, for the first time in my life, if horses ever need glasses.
They certainly spot things we don’t, and can judge a distance to a fence far better than most people. Still, I pondered the possibility that some horses out there could use a pair of lenses.
Google told me the answer immediately, which is, no they do not.
Did Mister Ed need glasses?
If you’ve ever watched the 60’s sitcom Mister Ed (the one with the talking horse), you might have seen the episode where Mister Ed goes off to college. He is shown donning a pair of smart spectacles whilst he conducted his studies. Turns out, he didn’t actually need them.
Eyes focus light on the retina, then the retina transforms the light into an electrical signal that is relayed to the brain. Humans, apparently, have been gifted a faulty focusing mechanism within our eyes, which I can attest to. I’m now at the stage of life where I must turn my book towards a powerful light source if I want to read. Very annoying.
Horses, on the other hand, rarely have issues with their eyes focusing light, which is why they don’t need glasses, contacts or a powerful light source.
20/60
I have a friend that brags about having 20/20 vision and I have never fully understood what that means other than they have perfect eyesight. Turns out it isn’t that tricky a notion, it simply means you can see something clearly from 20 feet away.
Horses, by contrast, are thought to have 20/30 – 20/60 vision, which correlates to them seeing something 20 feet away that we, with 20/20 vision (corrected or otherwise) can see from 30 or 60 feet away. In humans, this type of vision would be considered near normal to mild vision loss. Horses, therefore, see a little less detail than we do, so that hedge jump is a green thing to them, rather than a well-trimmed hedge with a million leaves.
Cats have 20/100 – 20/200 vision. Eagles, however, are eagled-eyed with 20/5 vision.
Color Vision
Horses do see in color, just not as vividly as we do.
The retina contains cells or cones that sense color. We have three cones, which sense red, yellow-green and blue light. Horses have only two cones, which sense yellow-green and blue, but no red. So, horses do see color, just in muted tones.
Night Vision
Horses’ eyes can filter ultraviolet light with a propensity falling somewhere between that of a nocturnal animal and a diurnal one. This is common in crepuscular animals, which is a new word for me, and means animals that are active during dawn and dusk. Horse eyes are able to use ambient near-ultraviolet light to see where they are going, which we humans are unable to detect. But once plunged into darkness our horses are just as lost as we are.
Eye Color
Most horses have big brown eyes. But you can sometimes find horses with blue (wall-eyed), green, yellow, amber or hazel eyes.
Blue eyes are due to a lack of pigment, and this lack of pigment reflects the light differently from the eye, making it appear blue. Blue eyes in horses are often related to large white facial markings, which brings less pigment with it leaving the eye either blue or partially blue.
Amber eyes, as well as hazel, green and blue may also appear in horses with a dilution gene such as a cream, pearl or champagne gene.
Tiger eyes are sometimes found in Paso Finos without any coat dilution. They are called tiger eyes because it references their yellow color. They can also be called goat eyes, but let’s face it, that doesn’t sound nearly as cool as tiger eyes. Either way, it is a gene mutation that causes this eye color.
Eye Placement
Our eyes are referred to as forward-facing, and most predatory animals have this placement. Eyes placed on the front of the skull allows for a wide field of binocular vision, enhanced depth perception, and some believe better night vision.
Our dear old horses on the other hand are prey animals, and therefore have laterally facing eyes. This lends itself to greater peripheral vision, a panorama if you will of around 350-degrees.
Unlike us, horses have both binocular and monocular vision. Each eye sees and moves independently, which is where their lack of depth perception comes in. But when they look straight ahead, their field of vision overlaps and gives them a binocular view complete with more depth perception. Horses move their head up or down to bring things into focus, and I think we’ve all seen our horses do this when they are trying to suss something out, like a tarp, perhaps.
Each eye feeds into the corresponding side of the brain with little crossover information. That’s why your horse might spook at the mounting block in the corner of the ring once when going to the left, and then again when going to the right. It’s all new information when you change rein. Nevermind the mounting block has been there for three years. That has nothing to do with their eyesight.
Horses do have a blind spot of approximately three feet directly in front of them and six feet behind them. They can also see the horizon and the ground at the same time, which I can’t even imagine. This is probably why your horse just keeps eating when you walk out into the field to catch them. They see you even if they aren’t looking at you. Creepy.
Anyway, all this fancy vision allows horses to hopefully spot that prowling lion behind them in the tall grass. You and I would just get wiped right out, none the wiser to the approaching cat.
Eyes and Ears
A horse’s ears and eyes operate together. If the left ear is pointed forward, the left eye is looking forward. And, as with the eyes, each ear works independently and listens separately, which sounds very confusing indeed.
The End
There you have it, the long and short as to why horses don’t need to wear glasses.
Sources:
vet.tufts.edu ; colorgentice.info ; nature.com ; equineguelph.ca
