Page 17 - New Mexico Fall 2020

Initiating an appropriate therapeutic plan from the beginning improves not only healing but often the long-term prognosis for the eye
There are essentially 2 forms of primary uveitis: acute uveitis and recurrent uveitis.
Interestingly, acute uveitis from any underlying condition can potentially lead a horse to develop the immune mediated Equine Recurrent Uveitis that many commonly refer to as Moon Blindness. Each uveitis episode causes some degree of damage to the structures of the eye creating a problematic long-term prognosis. More severe sequela includes corneal scarring, cataract formation, glaucoma, and retinal degeneration.
The potential causes of acute uveitis can be separated into infectious and noninfectious.
As the list of potential causes is almost
endless, your veterinarian will likely perform other diagnostic tests aside from a thorough
eye exam. Laboratory tests such as complete blood count, serum biochemistry analysis, and infectious disease serologic tests may be needed. The infectious causes of uveitis range from bacterial infections such as Leptospirosis (often implicated as the cause for Equine Recurrent Uveitis), Streptococcus, and E. coli to viral diseases like as EHV-1 and Equine Infectious Anemia. Other infections such as tooth-root
or hoof abscesses have also been identified as causes as have parasitic Onchocerca infections. Noninfectious origins such as trauma and neoplasia can also cause acute uveitis. The common denominator in developing acute uveitis is damage to the uveal tract with allows protein to leak into the aqueous of the eye which leads to the associated symptoms.
If an underlying cause can be identified, then treatment centers around that cause. If an underlying cause cannot be identified, symptomatic treatment of the eye itself becomes the main focus. The primary objective is eliminating the inflammation
and thus the pain from the eye. This is
where a careful eye examination becomes of paramount importance. Topical steroids such as prednisolone or dexamethasone are often the first medications of choice for uveitis, as they are powerful anti-inflammatories with excellent corneal penetration ability. However, if a corneal abrasion is present, the use of these medications can be profoundly detrimental
to the eye. Other mainstay medication
choices for acute uveitis involve the use of atropine and systemic anti-inflammatories
like phenylbutazone or flunixin as well as the addition of Aspirin.
Finally, another common eye condition not involving the cornea; laceration of the eyelid. Thanks to the anatomical location
of the eye on the horse’s head, and the very nature of horses, these injuries are extremely common. Often these injuries are identified rapidly by owners, but given the varied housing conditions of horses, occasionally it is days before the injury is identified and the horse presents for examination. The eyelid possesses excellent blood flow, completely contrary to the cornea, which allows for rapid and efficient healing. Surgical correction
is the only treatment option for eyelid lacerations, and these can almost always be corrected with the horse heavily sedated and standing. It is imperative that should an eyelid laceration be encountered, you resist the urge to cut off the hanging strip of lid, regardless of the condition you find it in initially. Removal of the affected portion
of lid causes exposure keratitis down the
road, effectively producing recurring corneal ulcerations simply because the horse has no way to protect its globe. After suturing the laceration, your veterinarian will perform a thorough eye exam to rule out the presence of
any other eye trauma that could lead to more severe problems going forward.
There are many other conditions that affect the eyes of horses with ulcerative keratitis, uveitis, and eyelid lacerations being the most commonly encountered. Anything we, as the advocates for our equine companions, can
do to intervene promptly when eye pain is encountered will ultimately lead to a happier and healthier horse. This begins with never assuming we know what is going on in and around the eye without a proper examination by a veterinarian. Initiating an appropriate therapeutic plan from the beginning improves not only healing but often the long-term prognosis for the eye.
Never assume you know what is going on in and around the eye without a proper examination by a veterinarian