Final Exam - Equine Uvea Flashcards by Madeleine Swindell

what is seen in this photo? is it normal?

corpora nigra/granula iridica - yes

dangling tissue from top of pupil

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how is the normal pupil oriented in the horse?

horizontally oriented

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where is the iridocorneal angle visible at in horses?

at the nasal & temporal limbus

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what are the stars of winslow?

end-on capillaries of the choroid that are visible in the tapetum

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what horses typically don’t have a tapetum lucidum?

blue eyed horses

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T/F: iris-to-iris persistent pupillary membranes are seen in all horses

true

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what is seen in this photo? is it normal?

iris-to-iris persistent pupillary membranes

yup

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what is seen in this photo? is it normal?

lack of tapetum & pigmented RPE exposing choroidal vessels

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what color eyes do you think this horse has?

blue - atapetal subalbinotic fundus

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what is this condition called?

heterochromia iridis

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what is uveitis?

inflammation of the uvea & break down of the blood barrier

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what is the most common cause of blindness in horses?

equine recurrent uveitis

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what horses are at risk for equine recurrent uveitis?

drafts, appaloosas, & european warm bloods

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does primary uveitis mean equine recurrent uveitis?

nope! must have 2 or more episodes to be considered equine recurrent uveitis

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what is panuveitis?

involves the entire uvea

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T/F: it is important to differentiate between acute uveitis & ERU because acute has many potential causes & ERU is an immune-mediated process

true

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what causes the development of ERU?

primary uveitis + environmental factors + genetic makeup + immune system dysregulation

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___________ is most commonly linked to ERU

leptospirosis

what are the 2 paths of the development of ERU?

infectious agent in the eye - agent is similar to retinal/uveal self antigens -> stimulates immune-mediated destruction

immune-mediated event -> intrinsic ocular proteins stimulate recurrent autoimmune destruction

is the presence of an infectious organism needed for continued disease of ERU?

nope

what are the 3 stages of ERU?

acute - how the disease presents during the early stages of a flare up

chronic - complications following several days of unrelenting inflammation or following multiple recurrent episodes of uveitis

end stage - complications of chronic unresolved inflammation leading to permanently blind eyes

what are the secondary risks you are trying to avoid for horses with acute uveitis?

corneal degeneration/ulceration

glaucoma

cataracts

retinal detachment

phthisis bulbi

what clinical signs are associated with acute uveitis?

aqueous flare, iris color changes, epiphora, conjunctival hyperemia, etc

what ophthalmoscope aperture setting is best for assessing aqueous flare?

small disc

what defines chronic uveitis?

cases that are refractory to therapy that remain painful & require persistent care with topical steroids negatively impacting corneal health long term secondary glaucoma is a risk factor

what clinical signs are associated with chronic uveitis?

band keratopathy!!!!! iris hyperpigmentation, posterior synechia, granula iridica atrophy, secondary cataracts

how is band keratopathy treated?

topical EDTA/antimicrobials, diamond burr debridement, & superficial keratectomy

what is band keratopathy?

mineral deposition in the cornea seen with chronic uveitis that increases the animal's risk of non-healing corneal ulcers

what lesion is shown in these photos?

band keratopathy

what lesion is shown here that is associated with chronic uveitis?

vitreal degeneration

what lesion is shown here that is associated with chronic uveitis?

peripapillary retinal degeneration - butterfly lesions & bullet hole scarring

what are the causes of blindness in end stage uveitis?

permanent corneal edema complete cataracts extensive synechiation secondary glaucoma - impaired outflow secondary to chronic inflammation retinal detachment/degeneration phthisis bulbi

what lesion is shown here in this horse with end stage uveitis?

phthisis bulbi

what serum titers may you consider for a horse with uveitis?

lepto, toxoplasma, lyme, & brucella

what are the treatment goals when working on a horse with uveitis?

preserve vision decrease pain & inflammation minimize permanent ocular damage prevent or minimize recurrence if possible - treat specific cause of uveitis

what treatment is indicated for equine uveitis?

treat aggressively & longer than usual - at least 2 weeks topical steroids, topical nsaids, & atropine systemic nsaids systemic abx based on suspicion of disease

what surgical options do you have for treating uveitis in horses? what are your best candidates?

cyclosporine implant - sustained release that decreases severity of flare ups & extends time between flare ups - takes 30-45 days to reach therapeutic levels & works for 2 years visual candidates in the early stages of disease with controlled inflammation

what therapy may you consider for horses with uveitis that aren't surgical candidates?

low dose gentamicin intravitreal injection good results for controlling inflammation & preventing recurrence

what complications are associated with horses with chronic uveitis being treated with low dose gentamicin therapy?

cataracts & retinal degeneration

what is the prognosis for horses with chronic uveitis (ERU)?

overall poor prognosis for vision!!! 50% will become blind despite therapy, some will be euthanized or enucleated, & others fully recover

what lesion is shown in this photo? what common locations are they seen in?

anterior uveal cysts - benign, fluid filled structure that may transilluminate corpora nigra, pupil margin, free floating in anterior chamber, & attached to the iris or ciliary body

when is treatment indicated for anterior uveal cysts?

when vision is impaired or the horse is spooking - refer for laser deflation

what lesion is seen in this photo? what animals are affected by it?

uveal melanoma - primary tumor more common in gray horses - no metastasis!!!!!!! but rapid growth in the eye can occur & cause secondary glaucoma

what treatment options do you have for uveal melanoma?

monitor with photo documentation sector iridectomy enucleation