What are Equine Recurrent Uveitis?
This condition is one of the most common eye problems in horses and is considered to be the leading cause of blindness. Equine recurrent uveitis is an immune-mediated disease. This means that your horse’s immune system is attacking the tissues in the eye, causing blindness.
A bloodshot eye and excessive tearing may be one of many indications that your horse needs veterinary care; treatment can minimize damage to the eye and provide relief from inflammation and pain as the disease progessses.
Equine recurrent uveitis or ERU is also known as moon blindness. Sometimes it is also called periodic ophthalmia.
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Symptoms of Equine Recurrent Uveitis in Horses
Daily checks of your horse’s eyes will alert you to any changes that may be taking place. If you notice the slightest change within your horse’s eye or eyes, err on the side of caution and schedule an appointment with your veterinarian. Things to watch for include:
- Sensitivity to light
- Holding the eye shut
- Small floating flecks in the front chamber of the eye
- Corneal edema
- Pus in the eye
- Pupillary constriction
- Haziness between the lens and the retina
- Inflammation of the retina and choroid
- Irregular flecks at the edge of the iris that shades the pupil
- Cataract formation
- Vitreous degeneration
- Vitreous discoloration
- Retinal degeneration
- Excessive tearing
- Bloodshot eye
There are three distinct types of equine recurrent uveitis that affect horses.
This is the most common type of ERU and is also known as anterior ERU. There are concurrent periods of pain and inflammation, which will last about two weeks followed by an unspecified amount of time where the disease is quiet. This pattern continues until the eye goes blind. Classic ERU is common in Appaloosa horses.
Also called subclinical ERU, this type of equine recurrent uveitis can be difficult to notice until the eye is already blind. Affected horses do not generally show signs of being in pain until signs of chronic ERU start to present. Insidious ERU is common in Appaloosa horses and Draft horses.
This is the least common type of equine recurrent uveitis. Inflammation develops behind the lens of the eye making retinal detachment, degeneration and vitreal opacities common. These will all lead to blindness. Posterior ERU is most common in Warmblood horses.
Causes of Equine Recurrent Uveitis in Horses
Researchers are somewhat baffled by equine recurrent uveitis. The exact cause has not been discovered and there is no link to genetics other than certain breeds of horses are more susceptible to ERU. Appaloosa horses, Paint horses, Draft horses and Warmblood horses are more susceptible. Standardbred horses and Thoroughbred horses are at a much lower risk of developing ERU.
Diagnosis of Equine Recurrent Uveitis in Horses
Equine recurrent uveitis, in its beginning stages, is very difficult to diagnose. Only after your horse has experience several recurrent episodes can a definitive diagnosis of equine recurrent uveitis be made. Your veterinarian may refer you to an eye specialist for a thorough eye examination to determine the damage that has already been done and begin specific treatments for your horse.
Treatment of Equine Recurrent Uveitis in Horses
This is a progressive disease that may eventually lead to complete blindness in the affected eye. Even immediate and aggressive treatments will not stop the disease from progressing.
There is no cure for ERU, therefore, treatments will center on the times that your horse is experiencing times of a flare up. Treatments will help to decrease inflammation within the eye, control the pain that your horse is feeling, minimize any damage to the structure of the eye and hopefully delay the onset of blindness in the affected eye.
Treatments will most likely run in cycles and will last at least four weeks at a time. Your veterinarian may prescribe anti-inflammatory medications, steroids and immunosuppressive medications.
In cases where your horse becomes difficult to handle to administer the needed medications, hospitalization may be suggested. During their stay in the hospital, your horse will have a subpalpebral lavage catheter inserted through the upper eyelid. This allows the medications to go directly onto the eye without having to fight your horse to do so.
New treatments that are being tested are showing promise to slow the development of ERU. These treatments must be performed by ophthalmologists. Horses that have had these surgeries have increased time between flare ups and the onset of blindness is significantly delayed.
Recovery of Equine Recurrent Uveitis in Horses
There is no cure for horses affected with equine recurrent uveitis. The main goal that your veterinarian will have for your horse is to delay the onset of complete blindness and offer relief when the disease flares up. Supportive care and treating the symptoms as they arise are the only options right now, unless you opt for the new surgical procedure, if your horse is a good candidate for this new surgery.