Eye Infections in Horses

eye infections in horses.2 Horses are infected with this parasite through flies, and they appear as thin worms in the eyes.Injury: Horses can develop an infection after having a foreign object lodged within the eye. If the eye's surface is scratched, environmental bacteria can quickly cause an infection. This could make the horse's eye appear cloudy and red. The horse will likely squint and tear profusely and may be reluctant to let you take a close look.

Diagnosing Eye Infections in Horses

A vet can usually diagnose an eye infection quickly through a physical examination of the eye, but the diagnosis doesn't always reveal a cause. Your horse may need to be sedated during this process. If the examination isn't conclusive, your vet may need to swab and test your horse's eye. Your vet will check for damage to the cornea as well as anything that may be lodged in the eye, such as splinters, awns from grasses, or grit. Developments in the microscopic corneal analysis have helped vets to identify funguses and bacteria in horses' eyes.

A tool called an in vivo corneal confocal microscope is used to perform this type of exam.3

Treatment

Swift action following diagnosis is key to successfully treating a horse's eye infection. Your vet may begin treatment with an ointment or gel to apply to the eye multiple times a day.4 If the infection is bacterial, your vet may prescribe antibiotic eyedrops. A horse with a fungal eye infection is likely to be prescribed a topical anti-fungal and may need surgery if ulcers are present. Treatment for ERU centers on managing inflammation and reducing discomfort. Topical inflammatories and corticosteroids can help but won't prevent future flareups.

Just because you may see improvement within a few days doesn't mean you should stop the medication before the entire course is up. Stopping treatment before the infection or injury is completely healed can result in the infection flaring up again and possibly causing more damage. In some cases, the cause of the infection (for example, bacteria) may become resistant to the medication if the full course is not administered.
When treating a horse with an eye problem, be aware that the infection may affect its vision, making it jumpier than usual. Talk gently, so you don't surprise your horse if you walk up on a blind-side.

Prognosis for Horses With Eye Infections

When treated swiftly, the prognosis for horses with mild eye infections is good. However, an untreated eye infection can lead to blindness and secondary infections.

The long-term prognosis for horses with ERU isn’t as optimistic. More than half of horses with ERU won’t be able to return to their normal levels of work and may become blind. Treatment will slow progression but is not curative.5

How to Prevent Eye Infections

Keeping your horse's environment as dust-free as possible can help stave off infection. If hay is dusty or bedding is very dry, you can dampen it or use other material or bedding. Make sure that sharp edges on water troughs, metal buildings, fences, or other obstacles are covered or inaccessible to prevent your horse from wounding its eye. Pound in or pull any old nails protruding from fences or other structures. Eye and face nets may help keep flies away from your horse's eyes. If you outfit your horse with a fly mask or veil, ensure it isn't irritating the eye.

Check your horse's eyes daily to catch the infection early and prevent it from worsening.

Types of Eye Infections in Horses

Conjunctivitis: Conjunctivitis is the swelling of the conjunctiva, the mucus membrane in the eye, sometimes caused by infection, allergen irritants, or foreign objects. The conjunctiva lines the inside of the eye and extends to the cornea. Conjunctivitis will cause discharge, redness, and discomfort, and if untreated, it can lead to complications like blindness.1ERU: Equine Recurrent Uveitis, or ERU, causes recurring bouts of inflammation in the eye and is the leading cause of blindness in horses. The blindness is often caused by equine glaucoma secondary to ERU. The development of ERU is complex and involves many factors, including injury, immune system issues, and viral infection.