Equine Recurrent Uveitis Flashcards
What is the term for inflammation of the uveal tract of the eye?
Uveitis
What is the leading cause of blindness in the horse?
Uveitis
Is ERU a primary or secondary cause of uveitis?
PRIMARY (it is a primary immune-mediated process, so there does NOT have to be anything elsewhere in the eye or in the body to initiate this recurrent inflammatory condition)
True or false: ERU is one specific disease process
False - it is a syndrome or group of diseases with similar manifestations
What part of the uvea is responsible for controlling the amount of light that enters the eye?
Iris
What part of the uvea is responsible for producing aqueous humor and anchoring fibers that suspend the lens (zonules)?
Ciliary body
What part of the uvea provides nutrition and oxygen to the highly metabolically active retina and is sandwiched between the sclera and retina?
Choroid
What type of inflammatory cells predominate when lymphocytic infiltrate begins to accumulate in the uvea and other eye tissues?
T cells, MHC Class II reactive
What is a key clinical sign of uveitis?
Miosis (unless there is secondary glaucoma)
What are 5 signs of acute uveitis?
Hypopyon, hyphema, aqueous flare, keratic precipitates, and fibrin
What is the hallmark sign of glaucoma in the horse?
Corneal edema (doesn’t have to be diffuse like in a dog)
What are Haab’s striae?
Breaks in descemet’s membrane (either ruptured or thinned) that become fibrotic
What is Phthisis bulbi?
The globe shrinks from chronic inflammation, and is considered end-stage for the disease process! This is an acquired condition (vs. microphthalmia which is congenital)
How do you diagnose ERU?
Rule out other primary causes of inflammation and use your history + clinical signs
What is the most likely pathogenesis of ERU?
Dysregulation of T-cell response with recurrent episodes due to epitope spreading (body is recognizing self as foreign)
True or false: Uveitis relapses can occur even in blind and phthisical eyes
True because of the persistence of auto-antigenic proteins (expression of ocular proteins continues to be impaired)
Are insidious uveitis cases bilaterally or unilaterally affected?
> 80% are bilaterally affected
A 5 year old Appaloosa mare comes to your clinic for a pre-purchase exam. The owner reports that the mare has never shown any signs of ocular pain, etc. On ophthalmic examination, you notice that the eyes are slightly red, and there is hyperpigmentation and posterior synechia along the iris. What are you concerned about in this mare?
Insidious uveitis (ERU) - these horses never have overt episodes and the casual observer may not notice a deterioration.
How many times more likely are Appaloosas to suffer from uveitis than other breeds?
8.3 times!
What infectious agent is a significant cause of uveitis worldwide?
Leptospirosis
What is the pathogenesis of Leptospira induced ERU?
Exact mechanism unknown but molecular mimicry highly suspected
How much more likely is an Appaloosa with a history of leptospirosis likely to lose vision?
3.8 times
What percent of horses with uveitis suffer corneal ulcers over time and why is this a concern?
> 25% - This is a concern because owners try to self treat (due to burnout and $$$) and may end up administering a steroid treatment in the presence of an undiagnosed ulcer!
What are the main goals for treatment of classic acute episodes of uveitis?
Dilate the pupil, control pain and inflammation
What topical medical therapies can be used in ERU cases?
Mydriatics, corticosteroids (prednisolone acetate or dex), NSAIDs, or cyclosporine
How long would you want to administer topical corticosteroids in a case of ERU?
Treat with corticosteroids at least 30 days past resolution of clinical signs! Don’t want to keep them on this forever because it causes immunosuppression of the cornea and predisposes to ulcers.
When is a vitrectomy contraindicated?
If there is extensive posterior synechia
What would you be concerned about if you saw a horse that had focal iris depigmentation and pigmented keratic precipitates?
Heterochromic Iridocyclitis (still an immune-mediated uveitis)
What breeds are overrepresented with HIK?
Warmbloods
A 10 year old Warmblood gelding presents to your clinic for corneal opacification and blepharospasm of the left eye. On your ophthalmic exam you find pigmented keratic precipitates, corneal edema, iris depigmentation, and retrocorneal membranes. What is the BEST differential diagnosis for this patient?
Heterochromic Iridocyclitis
A 10 year old Warmblood gelding presents to your clinic for corneal opacification and blepharospasm of the left eye. On your ophthalmic exam you find pigmented keratic precipitates, corneal edema, iris depigmentation, and retrocorneal membranes. You diagnose this patient with HIK, what are the medical treatment options for this patient?
Topical corticosteroids or NSAIDs + systemic NSAIDs
