How Horses See: Part Two

In my last blog post, I shared some information about normal equine vision from the University of Minnesota’s Trainers Series at the Leatherdale Equine Center.  In part two, I will recap the material on common eye diseases and disorders.

Part Two: Common Eye Problems

DIAGNOSIS

Just like humans, horses with eye problems may squint, have red eyes, have tears down their face, and their eyelids may swell up.  You might also notice your horse rubbing his eye on his leg or a fence post.  It’s easy to think, “Oh, he probably just caught a bit of hay or a speck of dust in his eye, he’ll be fine,” but unfortunately, in horses, severe eye problems look the same to an owner as minor ones.  Since early detection and treatment is crucial with major issues, it’s best to call the vet with any eye issues so they can test the eye to figure out the severity of the damage and treat it accordingly.

Corneal ulcers, when the cornea of the eye gets scratched, are one of the most common eye issues. However, that doesn’t mean they aren’t serious.  Equine eyes don’t have blood vessels in them so their eyes are more prone to developing infections and “melting ulcers” which are a very real threat to eye survival.  It’s important to seek veterinary attention promptly.

Equine Recurrent Uveitis (ERU) or moon blindness occurs when the inside of the eye becomes infected and is the most common cause of blindness in horses.  While the causes of this disease are not fully understood, vets have identified it as an auto-immune condition. The blindness is typically caused by cataracts, glaucoma, and deterioration of the retina.  Cataracts are most often seen in older horses, but can occur congenitally in foals as well.  Horses can also get conjunctivitis, aka pink eye, which is inflammation of the conjunctiva. 

You might also notice a small growth around your horse’s eye.  Squamous cell carcinoma, sarcoids, and melanomas are three types of cancer that can develop around a horse’s eyelid. These are more common in horses with white skin around the eyes and vets recommend such horses wear fly masks year-round to prevent excessive exposure to the sun. Early detection and surgical removal are recommended for cancerous growths around the eye.

TREATMENT

Since horses have extremely strong eyelid muscles, vets typically will sedate the horse in order to inspect it.  Then they often will apply a fluorescein or Bengal stain to the eye which coats irritated areas and highlights them.  This allows vets to determine the location, size, and depth of any ulcers.  Treatment typically involves an antibiotic topical ointment applied 2-4 times a day and an injection of banamine. 

Guardian Mask http://guardianmask.com/

Treatment of eye issues, especially in the case of recurring Uveitis, often involves special fly masks (like the Guardian mask above) with hard cups over the eyes to prevent the horse from rubbing the eye on everything as well as protecting the eye from debris and excessive sunlight.  

Use of normal fly masks can help prevent eye issues, especially irritation from flies and debris. Equine Sun Visor fly masks have a special solid fabric to block additional sun rays and act as sunglasses.

My horses wearing Equine Sun Visors - www.equinesunvisor.com

The best course of action is to prevent eye injuries when possible and always call your veterinarian about eye issues.

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