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IP 11 Ophthalmology > 13 - equine - pearce > Flashcards

13 - equine - pearce Flashcards

1
Q

do horses have better monocular vision or binocular vision?

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

A

better monocular vision -> 146*

binocular vision -> 65*

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2
Q

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

A

350*

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3
Q

where are blind spots in horse?

A

right in front of eyes and below chin

from behind ears to directly behind butt

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4
Q

t/f

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

A

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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5
Q

how many cones do horses have?

what colors can horse see?

what type of color blind are horses?

A

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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6
Q

basic needs for an ophthalmic exam in horse?

A

bright, focal light source
dark environment
magnification

same as with other species

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7
Q

is indirect or direct ophthalmoscopy recommended?

why?

A

indirect

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

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8
Q

what is needed for an indirect ophthalmoscopy exam in horse?

A

light source

16 Diopter lens

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9
Q

what size diopter lens for dog?

horse?

A

16 for horse

28 for dog

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10
Q

how to assess vision in horse?

what does pearce think is the best way?

A

vision directed behavior in stall
tracking
menace response

*best: vision directed behvaior

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11
Q

t/f

a good eye exam on a horse does not need sedation

A

false

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12
Q

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

A

xylazine

detomidine

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13
Q

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

A

restraint - stocks, twitch
sedation
topical anesthesia
nerve block

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14
Q

what topical anesthetic agent is used MC?

A

proparacaine

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15
Q

what motor nerve block is necessary for exam?

A

auriculopalpabral nerve block

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16
Q

what does the auriculopalpebral nerve block block?

what muscle is paralyzed?
what motion of the horse?

A

auriculopalpebral branch of the facial nerve (CrN 7)

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

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17
Q

t/f

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

A

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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18
Q

what drug used for the auriculopalpabral nerve block?

A

2% lidocaine or 2% mepivacaine

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19
Q

how long does the auriculopalpebral nerve block last?

A

lasts 1-3 hours

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20
Q

what are landmarks for the auriculopalpebral nerve block?

A

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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21
Q

t/f

the auriculopalpebral N block blocks both motor and sensory function

A

false - only motor

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22
Q

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

A

lacrimal N
zygomatic N
frontal N
infratrochlear N

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23
Q

when are sensory blocks done?

A

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

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24
Q

what is NORMAL intraocular pressure (IOP) in horse?

A

17-28 mmHg

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25
Q

what is necessary for accurate IOP measurement?

A

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

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26
Q

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

A

5 mmHg

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27
Q

what are 3 MAJOR equine ophthalmologic issues?

A

keratitis
SCC
equine recurrent uveitis

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28
Q

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

A

fungal

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29
Q

presentation of an acute superficial corneal ulceration?

A
  • distinct borders of epithelium lost
  • corneal edema
  • absence of cellular infiltrate or malacia of the stroma
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30
Q

Tx of superficial corneal ulceration?

A

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

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31
Q

frequency of abx for Tx of acute superficial corneal ulceration?

A

Tab QID for a week

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32
Q

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

A

pupillary dilation

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33
Q

what is a concern for using atropine in horses?

what is max use to lower risk of this occurring?

A

gut stasis / ileus may occur

2x day use MAX - more than that inc risk of ileus

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34
Q

how to Dx melting or deep stromal ulceration?

A

corneal cytology and corneal culture

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

35
Q

when should a corneal ulcer be referred?

A
  • over 1/2 stromal depth
  • rapidly progressive or melting
  • no neovascular response
  • perforated and actively leaking
36
Q

when is medical management used in tx of corneal ulceration?

A

until Sx can be performed

if owner cannot afford surgery

37
Q

t/f

if managed carefully, a deep corneal ulcer can be treated at home with the clients

why or why not?

A

false

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

38
Q

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

A

sub palpebral lavage tube

39
Q

what are 2 MC fungal corneal pathogens?

A

filamentous fungi - molds

Fusarium spp
Aspergillus spp

40
Q

t/f

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

A

true

41
Q

describe the pathology of equine ulcerative keratomycosis

A

presence of fungi

epithelial barrier disrupted -> inoculation of corneal stroma

42
Q

how to dx eq ulcerative keratomycosis?

A

cytology

culture

43
Q

tx of equine ulcerative keratomycosis?

A

standard ulcer
topical antifungal
surgery - often required

44
Q

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

A

fluconazole
itraconazole
voriconazole

45
Q

whatt are 2 imidazoles used to Tx fungal infections?

A

miconazole

ketoconazole

46
Q

what are 3 polyenes used to Tx fungal infections?

A

natamycin
nystatin
amphotericin B

47
Q

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

A

silver sulfadiaziazine

48
Q

what 2 fungal drugs are compounded?

A

itraconazole

miconazole

49
Q

what 2 fungal drugs are available at a human pharmacy?

A

voriconazole

natamycin

50
Q

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

A

voriconazole

51
Q

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

A

intact

52
Q

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

A

white - yellow stromal infiltrate

53
Q

t/f

a fluorescein stain is positive in the corneal stromal abscess

A

false

it is negative - epithelium is intact

54
Q

what is MC sequelae to corneal stromal abscess?

A

2* uveitis

55
Q

t/f

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

A

false

long term treatment is needed

tissue heals once it is vascularized

56
Q

how are corneal stromal abscesses treated?

A
  • topical abx every 4-6 hours
  • topical atropine to effect
  • topical antifungal
  • systemic NSAIDs
  • maybe systemic abx and anti fungals
57
Q

what abx are used to Tx corneal stromal abscesses?

why is abx selection very important in these cases?

A

fluroquinolones and chloramphenicol used often

abx must get thru the intact epithelium

58
Q

t/f

common Tx for stromal abscess is Sx excision and graft

A

false

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

59
Q

MC tumor of the eye and eyelids in equine?

*also the 2nd MC tumor in horse overall

A

SCC

60
Q

what structure does the SCC occur on?

A

3rd eyelid
conjunctiva
cornea
eyelids

61
Q

breed predilection to SCC?

A

draft breeds
appaloosa
color dilute horses

62
Q

describe behavior of SCC typically

A

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

but locally invasive

63
Q

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

A

local invasion

64
Q

t/f

surgery alone is best and most effective Tx for SCC

A

false

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

65
Q

Tx of SCC?

A

Sx and adjunct therapy

66
Q

best Px for SCC?

A

UV protection

67
Q

what is MC skin tumor in horses?

A

sarcoid

68
Q

sarcoid tumors are bengign or malignant?

A

benign - fibrous tissue

69
Q

what specific etiology is associated with development of equine sarcoids?

A

bovine papilloma virus

not strong direct link but DNA isolated in lesions via PCR

70
Q

what triggers sarcoids to develop?

A

trauma and biopsy - handle them carefully

71
Q

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

A

around legs

72
Q

what adjunct therapies are used to Tx SCC and sarcoids?

A 
freezing
radiation
hyperthermia
immunotherapy
chemotherapy
photodynamic therapy
73
Q

what breeds are at high risk for equine recurrent uveitis?

A

Appaloosa
European warmblood
draft breeds

74
Q

t/f

equine recurrent uveitis is a widspread dz but is easily treatable

A

false

is difficult to treat and frustrating…

75
Q

what is the common dz course of ERU?

A

initial uveitis episode
periodic uveitis episodes
chronic and recurrent

76
Q

what are acute signs of ERU?

A 
aqueous flare
keratic precipitates
keratitis
vitritis
chorioretinitis
77
Q

c/s of chronic ERU

A 
cataracts
synechia
iris hyperpigmentation
corpora nigra atrophy
glaucoma
blindness
phthisis bulbi => end stage
78
Q

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

A

retinal detachment
bird-shot retinopathy
butterfly lesion

79
Q

how is leptospira linked to ERU cases?

A

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

80
Q

what parasitic infection may lead to ERU?

A

oncocerca cervivcalis worm

81
Q

medical Tx options of ERU?

A

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

82
Q

sx tx options of ERU?

A

cyclosporin implants

83
Q

how effective are cyclosporine implants to Tx ERU?

how does this outcome compare with patients who did not get an implant?

A

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

84
Q

t/f

no matter what we do, most ERU horses become blind

A

true

56% of ERU horses in 2 years will be blind

IP 11 Ophthalmology (13 decks)

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