13 - equine - pearce Flashcards by Anna Delabar

do horses have better monocular vision or binocular vision?

what is the approximation of how much of each view the horse has?

better monocular vision -> 146*

binocular vision -> 65*

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what is the total visual panoramic field of the horse (degrees), btwn both monocular field and bonocular field?

350*

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where are blind spots in horse?

right in front of eyes and below chin

from behind ears to directly behind butt

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t/f

loss of one eye does not significantly effect a horse’s ability to function as it did with both eyes

false

significantly effects horse -> do NOT tell client the horse will be fine as it was before b/c this may set you up for legal problems

horse can live comfortably in the right environment but it will not function as it did before

one eyed horse at a disadvantage and may be more dangerous b/c of this handicapped -> make owner aware

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how many cones do horses have?

what colors can horse see?

what type of color blind are horses?

2 cones -> blue and red-green

see 2 basic hues -> yellow and blue; NO intermediate colors

“orange, red and light blue color blind”

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basic needs for an ophthalmic exam in horse?

bright, focal light source
dark environment
magnification

same as with other species

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is indirect or direct ophthalmoscopy recommended?

why?

indirect

better view of eye
direct is limited to mostly seeing the optic nerve head

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what is needed for an indirect ophthalmoscopy exam in horse?

light source

16 Diopter lens

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what size diopter lens for dog?

horse?

16 for horse

28 for dog

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how to assess vision in horse?

what does pearce think is the best way?

vision directed behavior in stall
tracking
menace response

*best: vision directed behvaior

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t/f

a good eye exam on a horse does not need sedation

false

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what drugs are used to sedate a horse during eye exam?

xylazine

detomidine

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what logistical things are needed for good eye exam of horse?

restraint - stocks, twitch
sedation
topical anesthesia
nerve block

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what topical anesthetic agent is used MC?

proparacaine

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what motor nerve block is necessary for exam?

auriculopalpabral nerve block

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what does the auriculopalpebral nerve block block?

what muscle is paralyzed?
what motion of the horse?

auriculopalpebral branch of the facial nerve (CrN 7)

orbucularis oculi M - akinesia of upper eyelid - horse cannot close eyes well

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t/f

during the auriculopalpebral nerve block, insert the needle directly into the nerve for most effective block

false

do NOT hit nerve

sub Q injection should be around nerve - then massage the injection site to help with absorption

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what drug used for the auriculopalpabral nerve block?

2% lidocaine or 2% mepivacaine

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how long does the auriculopalpebral nerve block last?

lasts 1-3 hours

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what are landmarks for the auriculopalpebral nerve block?

high point of zygomatic arch
Cd to bony process of frontal bone
Cd to posterior ramus of mandible

N lies on the zygomatic arch

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t/f

the auriculopalpebral N block blocks both motor and sensory function

false - only motor

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what regional nerve blocks are done to accomplish sensory nerve block?

lacrimal N
zygomatic N
frontal N
infratrochlear N

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when are sensory blocks done?

during some exams
for eyelid laceration repair
3rd eyelid surgery
biopsies of periocular area

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what is NORMAL intraocular pressure (IOP) in horse?

17-28 mmHg

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what is necessary for accurate IOP measurement?

calm animal avoid pressure on globe / lids natural, physiologic head position sedation and lid block

if there is over ____ mmHg pressure difference btwn the eyes, something is wrong

5 mmHg

what are 3 MAJOR equine ophthalmologic issues?

keratitis SCC equine recurrent uveitis

what type of infection are horses prone to in their cornea?

fungal

presentation of an acute superficial corneal ulceration?

- distinct borders of epithelium lost - corneal edema - absence of cellular infiltrate or malacia of the stroma

Tx of superficial corneal ulceration?

ID underlying cause Px 2* bacT infection atropine antifungal***

frequency of abx for Tx of acute superficial corneal ulceration?

Tab QID for a week

what is fxn of atropine to Tx acute superficial corneal ulceration?

pupillary dilation

what is a concern for using atropine in horses? what is max use to lower risk of this occurring?

gut stasis / ileus may occur 2x day use MAX - more than that inc risk of ileus

how to Dx melting or deep stromal ulceration?

corneal cytology and corneal culture *use sedation and lid block to scrape cornea, NOT eyelids b/c different flora there

when should a corneal ulcer be referred?

- over 1/2 stromal depth - rapidly progressive or melting - no neovascular response - perforated and actively leaking

when is medical management used in tx of corneal ulceration?

until Sx can be performed if owner cannot afford surgery

t/f if managed carefully, a deep corneal ulcer can be treated at home with the clients why or why not?

false ideal situation is a hospital where it can be medicated every few hours

what can be placed inferomedially in the horse's eye to aid in Tx equine eye dzz?

sub palpebral lavage tube

what are 2 MC fungal corneal pathogens?

filamentous fungi - molds Fusarium spp Aspergillus spp

t/f equine ulcerative keratomycosis is a sight threatening dz, even when well managed and treated appropriately

true

describe the pathology of equine ulcerative keratomycosis

presence of fungi epithelial barrier disrupted -> inoculation of corneal stroma

how to dx eq ulcerative keratomycosis?

cytology | culture

tx of equine ulcerative keratomycosis?

standard ulcer topical antifungal surgery - often required

what are 3 Triazoles used to Tx fungal infections in horse?

fluconazole itraconazole voriconazole

whatt are 2 imidazoles used to Tx fungal infections?

miconazole | ketoconazole

what are 3 polyenes used to Tx fungal infections?

natamycin nystatin amphotericin B

what drug is dr perace's favorite to treat fungal infections associated with a superficial ulcer?

silver sulfadiaziazine

what 2 fungal drugs are compounded?

itraconazole | miconazole

what 2 fungal drugs are available at a human pharmacy?

voriconazole | natamycin

which fungal drug is used off label for equine corneal dz but is well documented and proven to be efficacious?

voriconazole

in a corneal abscess, is the epithelium intact or broken?

intact

in corneal stromal abscess, what does the corneal stroma look like?

white - yellow stromal infiltrate

t/f a fluorescein stain is positive in the corneal stromal abscess

false it is negative - epithelium is intact

what is MC sequelae to corneal stromal abscess?

2* uveitis

t/f Tx of corneal stromal abscesses is simple and very rapid once initiated

false long term treatment is needed tissue heals once it is vascularized

how are corneal stromal abscesses treated?

- topical abx every 4-6 hours - topical atropine to effect - topical antifungal - systemic NSAIDs - maybe systemic abx and anti fungals

what abx are used to Tx corneal stromal abscesses? why is abx selection very important in these cases?

fluroquinolones and chloramphenicol used often abx must get thru the intact epithelium

t/f common Tx for stromal abscess is Sx excision and graft

false it is an option but is not done routinely - is only done if response to medical Tx is poor and Sx is required

MC tumor of the eye and eyelids in equine? *also the 2nd MC tumor in horse overall

SCC

what structure does the SCC occur on?

3rd eyelid conjunctiva cornea eyelids

breed predilection to SCC?

draft breeds appaloosa color dilute horses

describe behavior of SCC typically

slow to met and most will NOT (6-15%) but locally invasive

if left untreated, what will occur in cases of SCC?

local invasion

t/f surgery alone is best and most effective Tx for SCC

false Sx alone will lead to 40-60% recurrence of SCC

Tx of SCC?

Sx and adjunct therapy

best Px for SCC?

UV protection

what is MC skin tumor in horses?

sarcoid

sarcoid tumors are bengign or malignant?

benign - fibrous tissue

what specific etiology is associated with development of equine sarcoids?

bovine papilloma virus not strong direct link but DNA isolated in lesions via PCR

what triggers sarcoids to develop?

trauma and biopsy - handle them carefully

in addition to around the eye, where do sarcoids also occur commonly?

around legs

what adjunct therapies are used to Tx SCC and sarcoids?

``` freezing radiation hyperthermia immunotherapy chemotherapy photodynamic therapy ```

what breeds are at high risk for equine recurrent uveitis?

Appaloosa European warmblood draft breeds

t/f equine recurrent uveitis is a widspread dz but is easily treatable

false is difficult to treat and frustrating...

what is the common dz course of ERU?

initial uveitis episode periodic uveitis episodes chronic and recurrent

what are acute signs of ERU?

``` aqueous flare keratic precipitates keratitis vitritis chorioretinitis ```

c/s of chronic ERU

``` cataracts synechia iris hyperpigmentation corpora nigra atrophy glaucoma blindness phthisis bulbi => end stage ```

what lesions are seen on the fundus in cases of ERU?

retinal detachment bird-shot retinopathy butterfly lesion

how is leptospira linked to ERU cases?

when horse is infected w lepto bacT, the body develops immune response to the lepto Ag -> eye tissue is similar to the lepto Ag so the body may attack its own eye, after a lepto infection -> ERU cascade begins

what parasitic infection may lead to ERU?

oncocerca cervivcalis worm

medical Tx options of ERU?

immunosuppressants - systemic corticosteroids anti inflammatory drugs - systemic and topical NSAIDs dilating agent abx vax

sx tx options of ERU?

cyclosporin implants

how effective are cyclosporine implants to Tx ERU? how does this outcome compare with patients who did not get an implant?

good - for early cases and horses who are visual CSA has good penetration of ocular tissue and inhibits lepto 15% became blind, but much more than 15% who did not get implant became blind

t/f no matter what we do, most ERU horses become blind

true 56% of ERU horses in 2 years will be blind

13 - equine - pearce Flashcards

(84 cards)