How to Treat an Equine Eye Infection


Your horse's eyes are subject to many of the same vulnerabilities as your own, only he has little say in how well they are protected from dust, flies and many pasture perils. Many equine eye infections are uncomplicated and clear up with properly prescribed antibiotic therapy, while others are more stubborn or more serious and require lengthy, dedicated care.

  • For most uncomplicated infections, your vet will typically prescribe a topical ophthalmic antibiotic that you will apply to the affected eye two or more times a day. 
  • Your horse may need a fly mask if the infection results in sunlight sensitivity or if he needs drops that dilate his pupils. 


  • If your horse is squinting or has problems opening his eye, never force it open. Contact your veterinarian immediately.

The Healthy Eye

Knowing what your horse's eyes look like when he's healthy makes easier to discern any anomalies. His cornea should be clear and shiny, with no cloudiness, streaks or discoloration. Point a small flashlight into his eye and notice if his pupil contracts in response to the light.

A healthy horse will not have tearing from the corners, although occasional tearing is not necessarily abnormal, particularly after a dusty ride or on a windy day. Try a saline flush with an over-the-counter eye rinse. Persistent or prolonged tearing warrants a call to your veterinarian.


  • You can rinse your horse's eyes with sterile contact lens rinse solution; ensure it's the rinse and not the cleaning or storage solutions. Spray bottles can make flushes easier.

Signs That Something is Wrong

Anything other than temporary tearing from environmental irritants warrants a call to your veterinarian. The reason is simple: Even if you're relatively certain it's a condition you can clear up on your own with an ophthalmic ointment or rinse you have on hand, you don't know the type or source of infection, or whether the infection is secondary to a serious trauma to the eye that you can't detect.

Even an educated but erroneous guess could result in your horse's vision becoming impaired or lost completely. In some cases he could lose his eye.

Anything other than temporary tearing from environmental irritants warrants a call to your veterinarian.

Contact your veterinarian if you notice these irregularities in one or both eyes:

  • pink or red color;
  • persistent tearing or discharge of any color, with or without mucus;
  • swelling of eye or eyelid;
  • closed eyelids or squinting;
  • a seeming aversion to light;
  • eye rubbing (such as on his leg) or head-shaking;
  • a foreign object;
  • or cloudiness or obvious mark in the eye.

Common Infection Types


Conjunctivitis is simply an inflammation of the conjunctiva -- the protective membrane that lines your horse's eyelids. If the conjunctivitis is the sole issue, your vet may refer to it as pinkeye, or equine conjunctivitis, that occurs when bacteria make their way into your horse's eye membranes.


  • Viral pinkeye could be contagious through direct contact, so wash your hands carefully and put a fly mask on your horse if he is with other horses.

Corneal Ulcer

Most horses have many opportunities to develop a painful corneal ulcer, which is an injury -- such as a scratch -- to the sensitive cornea. The cause may be a seemingly benign but stubborn piece of hay, or a violent poke from a twig. Once the cornea is ulcerated, an infection can easily set in. Your vet may have to sedate your horse to thoroughly examine the cause and seriousness of a corneal ulcer.


  • Your horse may develop conjunctivitis as a secondary condition with a corneal ulcer, which is why a veterinarian examination is so important to determine the underlying cause of conjunctivitis symptoms.

Blocked Tear Ducts

Many horses experience occasional blockage of their tear or nasolacrimal ducts. Suspect this condition if you notice excessive and persistent tearing from one or both eyes. Your vet can usually diagnose this condition by using eye drops containing a dye. The duct of each eye descends into the corresponding nostril, so you should see the dye drip from that nostril after about 20 minutes.

If the dye isn't evident, your vet may insert a catheter to administer a saline flush that pushes any blockage up through the eyelid opening. This procedure is typically effective for most blockages. Your vet may prescribe preventive eye drops once the blockage is cleared.

Equine Recurrent Uveitis

A diagnosis of equine recurrent uveitis, commonly referred to as moon blindness, is something no horse owner wants to hear. The exact cause of this condition is uncertain, but it often results in blindness in the affected eye. One suspected cause is the Leptospirosis bacteria, which can be transmitted to horses through contact with other infected animals, or through contaminated soil. Regardless of the source, the horse's immune system attacks the eye rather than the underlying condition.


  • Plan a prolonged treatment regimen to hopefully curtail the progression of uveitis; an equine ophthalmologist may implant a medicated disk into the affected eye that releases medication. You will likely have to administer additional eye medications.

Getting the Medication Into the Eye

Fortunately, effectively applying your horse's eye ointment or drops doesn't require you to hold both his upper and lower lids open.

  1. Halter your horse, then gently roll down only his lower lid. 
  2. Place the prescribed amount of ointment or drops on the inside of the lower lid, being careful not to touch the applicator tip to his eye. 
  3. Then release his eye. As your horse blinks or closes his eyes, he'll automatically spread the ointment across his cornea.


  • You can also place the required amount of ointment on your finger and rub it onto his lower lid. Be sure to wear disposable medical gloves and use fresh gloves for each application.

For serious conditions, your vet may insert a subpalpebral lavage system. It may seem intimidating, but this can actually make it easier for you to administer the medication while ensuring that the correct dosage goes to the correct place. Your vet will sedate your horse to insert the system, which is flexible tubing that extends from one of your horse's eyelids, to the outside of the horse. You then inject the medication into the easily accessible outside end of the tube.

Preventing Eye Infections

Putting a fly mask on your horse can reduce or prevent many infections, particularly those transmitted by flies and insects. It can also protect the eyes from dust, hay and pasture pokes. Keep your barn as dust-free as possible, and implement good barn management to help control fly and insect populations.

Follow up with your vet following any infection treatment, even if your horse seems to have completely recovered.


  • Always apply the full course of antibiotic treatment even if your horse seems better after a few days. Prematurely ending treatment could result in a recurrence.

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