Eye Problems and Eye Diseases in Horses

 

  • You may recall, from previous articles about when to call the vet, that eyes do not grow back. You may also be curious to know that eye problems are off the scale in terms of pain. It’s in your horse’s best interest to involve your veterinarian at the earliest sign of any eye issue.

 

  • I also talked to my own vet today about eye issues – and she said: “Every day you wait with an eye issue increases your bill by about $1000.” Surgeons and specialists and hospital visits can be necessary if things are not addressed quickly.

 

  • But enough of the drama – let’s chat about horse eyes, how they work, what can go wrong, and how you can spot things early.

 

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How horse eyes “work”

 

Horses, being delicious meals for other creatures, have developed eyesight that can keep them apprised of potential killers.

 

  • They are able to see almost all the way around, save for a few feet directly in front of them, and a few feet behind them. You may also notice that a horse will walk towards you exactly straight, but adjust his head or start to go off to one side, so that he keeps you in his vision as he comes closer.

 

  • The horse eye has a few layers to know about. The sclera, or white part of the eye, is an outer layer and made up of fibers. The cornea is the clear, rounded portion of the eye in the front. Then there’s a vascular layer, which just means it has a blood supply. This vascular layer is the colored iris, the ciliary body behind the iris, and the choroid, which is under the retina at the back of the eye. The inner eye has a layer of nervous tissue that makes up the retina.

 

  • Behind the iris is also the lens. The iris can also open and close to let light in, or not. This hole is the pupil. The lens and cornea are at the front of the eye, and get to spend time in the aqueous humor. This fluid keeps things lubed up and helps bring oxygen to these parts, in addition to bringing vitamins and taking away waste.

 

  • But what about the center of the eye? That’s virtreous humor and it does a few things. Like hold the retina in place (important) and also is a shock absorber (also important).

 

  • But what can we clearly see of the eye? Or mostly see? The sclera is covered by conjunctiva, as is the “inside” of the eyelids. Horses also have a third eyelid, which you can see in the corner of his eye towards the center of his face. It’s really obvious in cats, too.

 

  • As light passes through the cornea and lens, along with the aqueous and vitreous humor. It hits the retina, is converted to electrical impulses, and sent along to the brain for deciphering. The retina has cells called rods and cones, rods work with light, cones work with color. Horses can see some colors, mostly blues, red, greens.

 

close up of gray horse eyelashes

 

Common eye issues in horses.

 

Entropian.

 

Starting with a creepy one – horses can get what’s known as entropian. This is when the eyelids tuck towards the eyeball, and the eyelashes are rubbing up against the eyeball. It’s common in some squishy faced dogs, also. It can be treated with surgery.

 

Corneal ulcers.

 

  • This can go one of a few ways. Corneal ulcers can be superficial, or all the way down into the eyeball with a deep corneal laceration. A simple ulcer of the cornea is caused by a scratch, of which there are hundreds of possible ways that horses can do this to themselves. By standing and breathing for example. Simple ulcers, while excruciatingly painful, can usually be healed with topical eye meds.

 

  • With corneal ulcers, you might notice your horse tearing up, squinting a lot, rubbing his eyelids on his knee, avoiding the sun, and maybe with some swollen eyelids. Any of these things loosely translate into “call the Vet pronto”.

 

  • Your vet will do an exam, and might even stain the eye a delightful shade of yellow-ish green to check for ulcers and lacerations.

 

  • Some ulcers need a temporary tube placed under the eyelid to easily administer medications. This is called a subpalpebral lavage (SPL) and sounds horrifying, but makes your life easier if you need to be applying meds 8 times a day, which can happen.

 

  • This is super important – some eye meds contain steroids, and some don’t. A corneal ulcer requires specific meds, so don’t put anything in your horse’s eye until the Vet has seen it. When you call the Vet, ask about giving some pain relief as they are driving to you to check things out.

 

  • One more thing about corneal ulcers – they can easily get infected. With bacteria. Or fungus. Or both. Untreated corneal ulcers can head down the road to infections or even a ruptured eye. BLECH.

 

close up of horse eye with green stain

The remnants of a green stain used to examine the eye.

 

Corneal lacerations.

 

  • These injuries to the eyes are like ulcers, but extend into the eye ball and are infinitely more serious than the already serious corneal ulcer. Many lacerations require surgical repair.

 

  • When a horse’s eye is lacerated, vision might also be impaired. The Vet will often find the iris out of place, blood and/or pus in the eye, aversion to light, and the usual signs that go along with a corneal ulcer like squinting and swelling.

 

Eyelid injuries.

 

  • This might be the luckiest of eye injuries, and sometimes require sutures. Sometimes not. You might find a bit of bleeding with an eyelid cut, but don’t rule out other corneal issues if you find one of these, call your vet anyway.

 

horse wearing a fly mask with ears and full nose coverage

Fly masks are a must for eye issues!

 

Uvitis, also knows as Equine Recurrent Uvitis (ERU)

 

  • Uvitis, is basically UV-itis, meaning that UV light from the sun causes inflammation of the eye. You may also hear this called moon blindness. This condition is called moon blindness, as it was once thought to cycle with the moon because it does come and go. This is something your horse will live with forever, and maybe it’s manageable, and maybe it gets worse over time.

 

  • There’s no cure for uvitis, and can lead to scars, cataracts, glaucoma, and even blindness. There are also boatloads of theories as to why this happens, but the bottom line is that it does.

 

  • Inside the horse’s eye, the inflammation targets the uveal tract, which is the layer of tissue between the outer layer that houses the cornea and the inner layer, which contains the retina, iris, and choroid. When this swells, the pupil gets very small due to contraction, which is also quite painful.

 

  • You may also see broken blood vessels, a cloud or haze over the eye, or even deposits of pus. Yes, it’s gross, and yes it can be managed. Some horses show no signs until blindness sets in.

 

  • Medications are often used to reduce the inflammation of uvitis. This will also dilate the pupil, which can make your horse even more sensitive to light.

 

  • Horses with uvitis can be helped by staying ahead of flare-ups. Some horses do best with fly masks, that can even be modified to cover the affected eye and create total darkness under the mask on that side. You may need to consider different turn out times and the best medications to use.

 

  • Your vet can also help you learn what to look for in your particular horse.

 

Cancers around the eye.

 

 

  • Skin cancers and other conditions can invade the eye area of your horse. You will likely see something growing around the edges of your horse’s eye. As with all tumors, getting them checked early is best.

 

  • There’s a type of cancer called squamous cell carcinoma that can happen around your horse’s eye. The third eyelid is a commonplace for it, as it the conjunctive, cornea, and even eyelids. The tumor tends to be pink, a bit lumpy, and rough to the touch, or it looks like a sore. These jerks of a cancer can easily spread deep into the eye and the tissues surrounding the eye.

 

  • For horses with pink skin and pink eyelids are most at risk. UV light tends to also increase the risk of squamous cell carcinomas in horses.

 

  • Squamous cell carcinomas can be surgically removed, and sometimes the entire eye needs to be removed as well.

 

  • Melanomas, the most “famous” of gray horse tumors, can also happen in the eye area. These can be treated with oral medications in some cases, removed by a surgeon, or frozen off.

 

  • Sarcoids are another type of tumor that can affect your horse’s eyes. It’s believed that sarcoids have a viral component to their development. Sarcoids have a variety of treatment options, from chemical lotions to oral medications to anti-cancer drugs injected directly into the sarcoid, to surgery, and even having them frozen.

 

Is there more? Yes. Glaucoma.

 

  • This is a disease of the eye that can damage the retinal nerve, which sends the images your horse sees to his brain. Glaucoma is an increase in the pressure inside the eye, which damages the retina and the optic nerve, and can lead to blindness.

 

  • Some horses with uvitis will develop glaucoma as a complication, and some horses just get regular (?) glaucoma by itself. Either way, it’s painful. You can help the horse with glaucoma by using medications and perhaps exploring laser surgery options. Most eyes with glaucoma should be removed after blindness as the pain is quite great at that stage.

 

Cataracts

 

  • These sight stealers are a clouding of your horse’s lens. Some are tiny, and some are not. Some cause blindness, some do not. Cataracts can happen as a result of an injury, or it’s simply your horse’s genetics that create them. Uvitis can also cause cataracts.

 

 

vet giving eye exam to horse

Quick peeper check

 

How to tell if your horse is having vision issues.

 

  • Horses that are going blind or struggling with vision often move about their worlds differently. Light can be overpowering, and often the transitions between sun and shade are tricky to navigate.

 

  • As depth perception will change with vision loss, your horse might be nervous or confused moving around smaller spaces or through doorways. Your horse’s behavior might also be more cautious or spooky than normal, and you might see some or all of the eye starting to get cloudy.

 

  • If ever there was a time to memorize your horse, this is it. You need to know his normals like they are the back of your hand. Any change should be noted and discussed with your Veterinarian.

 

  • Here’s to hoping that your horse is obviously trying to tell you something when it comes to his eyes. Swelling, oozing, funny smells, rubbing, hair loss, weird colors, tearing up, lumps, excessive boogers, anything not normal.

 

  • Fly masks, low dust, daily checks, proper eye exams during routine Vet visits, and working turnouts around sun and shade can help your horse.

 

 

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