The Equine Eye

We've treated over twenty eye injuries and illnesses this winter (so far!) and it seems about time to tell you what's so important about them, and what different conditions you may be witnessing.

Why your horse’s eyes are important

As we know, equines evolved as prey animals. This means that many of a horse’s physical adaptations exist to help him avoid becoming a predator’s dinner! Your horse’s eyes are no exception. Their large size and lateral (on the side of the head) position provide a wide field of view, making horses very good at spotting predators (or scary plastic bags) in the distance.

Horses are also herd animals. Eyesight is a very important asset in these social settings, as body language makes up a large part of communication between herd mates.

Many equine eye conditions can progress rapidly if not properly diagnosed and treated, possibly leading to loss of vision or requiring surgical removal of the eye. Equines rely heavily on their eyesight in daily life, so it is important to contact your veterinarian immediately if any eye problems occur.

When to call the veterinarian

You should contact your veterinarian any time you are concerned about your horse’s eyes. Here are some examples of potential reasons to make a phone call:

  • Trauma involving the eye or eyelids - Horses are strong and fast. These qualities can sometimes be detrimental in confined spaces, leading to eye injuries requiring veterinary attention.
  • Eye pain - Signs to look for that may indicate your horse’s eyes are painful and in need of veterinary evaluation include squinting, watering, and yellow or green discharge. Another, more subtle sign of unilateral eye pain that veterinarians look for is eyelash orientation - a horse’s eyelashes may point down slightly (instead of straight out) in the uncomfortable eye.
  • Vision problems - You may suspect changes in your horse’s vision if you see an increase in “spooky” behavior, or notice him bumping into things on one side. A horse with changes in vision may also be reluctant to move from light (such as the pasture) to dark (such as the barn aisle), or vice versa.
  • Change in appearance of the eye - An eye that is suddenly swollen, cloudy, bulging, or sunken in appearance warrants veterinary attention.

Examples of eye conditions

Eyelids and surrounding tissues

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  • Eyelid lacerations - A horse’s eyelids function to provide crucial protection to the eye. Most eyelid injuries require prompt repair by a veterinarian.
  • Conjunctivitis - Inflammation of the conjunctiva (the tissue inside the eyelids, surrounding the eye) will present as redness and swelling. This may arise from environmental irritants, and is a common finding in the summer when flies are active.
  • Allergic reaction - Conjunctivitis and eyelid swelling may be an indication of an allergic response requiring veterinary attention. Bee stings are a potential cause of a swollen eye during the warm summer months.
  • Blocked nasolacrimal duct - Consult your veterinarian if you notice a significant amount of tears draining from one or both of your horse’s eyes. A blocked tear duct may be to blame, especially if the eye does not show other signs of pain or inflammation.
  • Masses - Occasionally a horse may develop growths on the eyelids or conjunctiva, such as squamous cell carcinoma or sarcoids. Any abnormal growth on or near the eye should be evaluated by a veterinarian.
  • Orbital fracture - Fractures of the bony orbit surrounding a horse’s eye should be evaluated by a veterinarian.

Cornea

  • Superficial corneal abrasions/ulcers - Your veterinarian will likely perform a corneal fluorescein stain during an ophthalmic exam. This test demonstrates whether the surface of the cornea (the clear, glistening surface of the eye) is intact, allowing us to assess whether a scratch or ulcer is present. Any time the surface of the cornea is damaged, this puts the cornea at risk for bacterial or fungal infection. As with many eye conditions, an infected corneal ulcer needs early and aggressive treatment to provide the best chance of maintaining vision. Your veterinarian may also suggest performing a cytology or culture to determine the most appropriate treatment plan.
  • Corneal scars - Your veterinarian can help differentiate between a new injury requiring treatment and a corneal scar, which may simply be a cosmetic remnant of a prior injury.

Interior

  • Cataracts - Opacification (or increased cloudiness) of the lens in a horse’s eye may occur for a number of reasons, and may or may not be cause for changes in management. Consult your veterinarian to discuss any changes in the appearance of your horse’s eyes.
  • Equine recurrent uveitis - This is a painful condition involving inflammation of the structures within a horse’s eye.

How to manage equine eye problems

Depending on the condition, treatment for an equine eye condition may be as simple as monitoring or medicating at home. Alternatively, some conditions may require referral to a veterinary hospital for more extensive evaluation and treatment. You and your veterinarian will work together to determine the best treatment plan for your horse’s eye condition.