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Special Topics in Equine Clinical Practice > Equine Uveal Disorders > Flashcards

Equine Uveal Disorders Flashcards

1
Q

What are the 3 components of the uvea?

A
  1. Choroid (posterior uvea)
  2. Ciliary body (anterior uvea)
  3. Iris (anterior uvea)
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2
Q

What pathologic process is degeneration of corpora nigra associated with?

A

chronic equine recurrent uveitis

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3
Q

What are 4 clinical signs that differentiate CHRONIC anterior uveitis from acute anterior uveitis?

A

Chronic anterior uveitis has many of the same clinical signs as acute anterior uveitis (blepharospasm, miosis, epiphora, aqueous flare, hypopyon, hyphema, etc.)

Chronic cases are usually differentiated by the presence of cataracts, retinal detachment, secondary glaucoma, and phthisis bulbi.

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4
Q

What are 3 etiologies for acute anterior uveitis in horses?

A
  1. keratitis (ulcerative or abscess)
  2. trauma
  3. sepsis (neonatal)
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5
Q

What are 3 potential etiologies for equine recurrent uveitis?

A
  1. Leptosporosis*
  2. onchocerca cervicalis
  3. immune-mediated/hypersensitivity
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6
Q

which horse breed is predisposed to equine recurrent uveitis?

A

appaloosas

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7
Q

Describe the difference between the classic versus insidious forms of ERU

A

Classic – intermittently severe episodes of uveitis

Insidious – chronic, low-grade inflammation, non painful; degenerative changes are starting to occur slowly (cataracts, posterior synechiae, retinal detachment)

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8
Q

T/F: ERU is a very common cause of blindness in horses

A

true
Moon Blindness is the MOST common cause of blindness in the horse

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9
Q

You are examining a horse with possible ERU. What might your anterior segment look like on exam?

A

miosis
aqueous flare/hypopyon
posterior synechia

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10
Q

You are examining a horse with possible ERU. What might your posterior segment look like on exam?

A
  • vitreal debris/ liquefaction (greenness)
  • chorioretinitis
  • retinal detachment
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11
Q

What are chronic changes associated with ERU?

A
  1. cataracts
  2. posterior synechia
  3. retinal detachment
  4. secondary glaucoma
  5. phthisis bulbi
  6. iris hyperpigmentation
  7. corpora nigra atrophy

many others: corneal edema, corneal vascularization, keratoprecipitates, lens subluxation

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12
Q

What is the ‘butterfly’ lesion?

A

peripapillary edema associated with retinal inflammation and scarring.

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13
Q

How would you go about diagnosing a potential case of ERU?

A

Most impt: History and clinical signs

Other things you can do:
- lepto serology titers
- conjunctival biopsy (onchocerca)
- ocular ultrasound (if you cant see the back of the eye)
- CBC/Chem (not really useful)

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14
Q

How do you MEDICALLY treat ERU?

A
  1. Systemic NSAIDs (check renal function first because they will likely be on these for >1 month)
  2. topical corticosteroids (stain eye to r/o ulcer first)
  3. topical atropine (measure IOP first, dont give if increased IOP)
  4. +/- systemic antibiotics (penicillin/gentamicin, doxy, or enrofloxacin) if underlying cause is infectious

Rule of thumb: Place suprapalpebral lavage system for easier daily treatments. Treat aggressively until the symptoms are controlled, then gradually taper medications to minimize risk of relapse.

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15
Q

what are the 3 benefits to prescribing topical atropine in a horse with ERU?

A
  1. dilates pupil (decreases risl of posterior synechiae)
  2. controls ciliary body spasms (pain control)
  3. stabilize blood-aqueous-barrier
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16
Q

What are 3 options for surgical treatment of ERU?

A
  1. Suprachoroidal cyclosporine implant – successful and lasts 3 yrs
  2. Vitrectomy – reduces inflammation but high incidence of forming cataracts
  3. Intravitreal gentamicin – lasts 1 year
17
Q

What are recommendations you can give to an owner whose horse was just diagnosed with ERU. They already opted for medical treatment so your recommendations would be ancillary things they can help with as an owner.

A
  1. environmental modificaiton – change pasture/stable, change bedding type, decrease dust exposure
  2. general health maintenance – anthelmintics, vaccination, hoof and dental care.
  3. test before breeding!
18
Q

What is the prognosis for ERU?

A

long-term for vision retention = poor

blindness is usually due to secondary cataracts, glaucoma, and/or retinal detachment

19
Q

what is the most common and most problematic uveal cyst type?

A

idiopathic cystic corpora nigra

20
Q

how can you distinguish a uveal cyst from a melanoma?

A

cysts will transilluminate (light will pass through them)
melanomas will not.

21
Q

T/F: cystic corpora nigra can disturb vision

A

true because the cyst obstructs the pupil

you can do a standing laser treatment

22
Q

What are 3 etiologies of chorioretinitis in horses?

A
  1. equine reccurent uveitis
  2. equine herpes virus
  3. trauma
23
Q

what clinical sign / finding indicates chorioretinitis caused by ERU?

A

peripapillary retinal edema or scarring (butterfly lesion)

24
Q

T/F: there is no specific treatment for chorioretinitis

A

true

im guessing you just manage the underlying cause (ERU, EHV, trauma, etc.)

25
Q

what clinical finding indicates chorioretinitis caused by EHV-1?

A

bullet hole lesions

if there are >20 lesions, visual deficits are likely.

26
Q

You are called to a farm to evaluate a horse because the owner claims that at night, he keeps bumping into things. Your presumptive diagnosis is congenital stationary night blindness. Which of the following statements would NOT accurately reflect this diagnosis?
A. this horse should have normal day vision
B. this horses retina will be abnormal
C. appaloosas are most commonly affected
D. there is no treatment for this condition

A

B. this horses retinal will be abnormal

This horses retina would appear normal with this condition.
That is why electroretinogram is required to diagnose it.

27
Q

how do you diagnose congenital stationary night blindness?

A

electroretinogram

28
Q

What are 4 causes of acquired equine vision loss and which of the 4 are more common?

A
  1. ERU *
  2. Glaucoma *
  3. traumatic optic neuropathy
  4. exudative optic neuropathy
  • indicates more common causes.
29
Q

T/F: traumatic optic neuropathy (shearing of the optic nerves/chiasm caused by trauma) leads to acute blindness but can be reversible with surgery and medical treatments that promote optic nerve regeneration

A

false – causes acute blindness that is irreversible!

Special Topics in Equine Clinical Practice (18 decks)

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