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LA DX & TX II > Final Exam - Equine Conjunctiva & Cornea > Flashcards

Final Exam - Equine Conjunctiva & Cornea Flashcards

1
Q

why do you need to pay attention to the eyelash angle in horses?

A

changes in angle can indicate blepharospasm

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2
Q

why are periocular nerve blocks needed for ophthalmic exams in horses?

A

needed due to the strength of the eyelids, pain control, accurate diagnostics, sterile sample collection, etc

horses will hurt themselves if you skip this

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3
Q

how are horse eyelids opened?

A

index finger engages the supraciliary sulcus

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4
Q

what two nerve blocks are done in the horse prior to an ophthalmic exam? what do they block?

A

auriculopalpebral block - blocks motor

supraorbital block - blocks sensory of the upper eyelid

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5
Q

what nerve block is shown in this photo?

A

auriculopalpebral

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6
Q

what nerve block is shown in this photo?

A

supraorbital

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7
Q

where is the schirmer tear test strip placed in the horse eye?

A

placed in the lower lateral eyelid

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8
Q

what is the minimum database for equine ophthalmic exams?

A

schirmer tear test - uncommon in horses, needs to be > 15 mm/min, of basal & reflex tearing

fluorescein stain - to check for corneal ulceration, nasolacrimal patency, & corneal perforation

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9
Q

what are the 5 components of corneal anatomy?

A
  1. tear film
  2. epithelium
  3. stroma
  4. descemete’s membrane
  5. endothelium
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10
Q

what is the most sensitive structure in the horse’s body? why?

A

cornea

has the ophthalmic division of the trigeminal nerve - greater nerve density antervior vs posterior

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11
Q

what are the 3 main anatomic regions of the conjunctiva?

A

palpebral conjunctiva - lines superior & inferior eyelids

bulbar conjunctiva - covers the anterior aspect of the globe to the limbus

fornix conjunctiva - junction of the palpebral & bulbar conjunctiva

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12
Q

what is the conjunctiva?

A

non-keratinized stratified columnar cells continuous with the corneal epithelium

covers the anterior & posterior aspect of the 3rd eyelid

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13
Q

what is the purpose of setting up a sub-palpebral lavage system?

A

allows for safe drug administration comfort, & less medication waste

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14
Q

after the placement of a SPL, what should be done?

A

protective masks should always be worn after placement to prevent damage or rubbing to the system!!!

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15
Q

what congenital lesion is shown in this photo? what is the treatment of choice?

A

dermoid (choristomas) - non-progressive lesion that consists of epithelial & dermis-like components found in an abnormal location that most frequently arise from the limbus

complete surgical excision done either standing or under general anesthesia that usally heals by 2nd intention as the lesions are generally superficial

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16
Q

what do you need to do for a definitive diagnosis of a dermoid in a horse?

A

need to submit it for histopathology

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17
Q

what horses are generally affected by the congenital condition of megalocornea & cornea globosa?

A

rocky mountain horses, kentucky mountain horses, mountain pleasure horses, morgans, belgians, american mini horses, & icelandic horses

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18
Q

what is the coat color association of horses & megalocornea/cornea globosa?

A

chocolate colored coats with white manes & tails

genetic mutation PMEL17 - gene responsible for silver coloration

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19
Q

what condition is shown in this photo? what clinical signs are seen? when do we see it most often?

A

eosinophilic conjunctivitis

white raised plaques on the cornea/conjunctiva, blepharospasm, & mucoid discharge

summer months

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20
Q

how is a horse diagnosed with eosinophilic conjunctivitis?

A

eosinophils & rare basophils seen on cytology

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21
Q

how do you treat a horse with eosinophilic conjunctivitis?

A

oral steroids, oral antihistamines, & topical antibiotics

topical steroids aren’t recommended

topical immunomodulators & antihistamines are acceptable but not the best

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22
Q

what follow up needs to occur for a horse with eosinophilic conjunctivitis?

A

recheck in 2 weeks & then follow up monthly - 33% of horses reoccur!

takes 2.5 months for them to heal

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23
Q

what causes KCS in horses? is it common?

A

associated with loss of parasympathetic nerve supply to the lacrimal tissue through the facial nerve

uncommon - deficiency in tear film

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24
Q

what clinical signs are seen in horses with KCS?

A

mucopurulent discharge, corneal neovascularization, dry corneal surface, & possible facial nerve paralysis

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25
Q

how is KCS diagnosed in horses?

A

STT < 10mm/min
radiographs/CT/endoscopy

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26
Q

how is KCS treated in horses?

A

topical tear stimulant (cyclosporine or tacrolimus), topical tear replacement, & topical abx for corneal ulcers

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27
Q

what surgical options are available for treating a horse with KCS?

A

can do a partial tarsorrhapy if facial nerve paralysis is present - helps manage dryness

cyclosporine implants

parotid duct transposition

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28
Q

what follow up is indicated for a horse with KCS? what is the prognosis?

A

2-4 week recheck

guarded prognosis due to lifelong therapy needs

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29
Q

what condition is shown in this photo of a horse’s eye?

A

KCS

30
Q

what lesion is shown in this photo? what treatment is indicated? how long will it take to heal?

A

simple corneal trauma - no signs of infection or stromal loss

topical abx 3X a day, atropine sulfate in clinic, & NSAIDS - may need to consider topical anti-fungal therapy to prevent fungal keratitis

should heal within 1-2 weeks

31
Q

what lesion is shown in this photo? what are some big causes of it?

A

complex corneal ulceration - evidence of infection, melting ulcer (keratomalacia) - endogenous proteinases from the body & bacteria makes it melt

staph, strep, pseudomonas, & aspergillus

32
Q

what treatment is needed for complex corneal ulcers?

A

apply a SPL, atropine sulfate, voriconazole (fungal), fluoroquinolone abx (moxifloxacin), anti-melting medication - serum, EDTA, tetracycline abx, & n-acetylcysteine

systemic NSAIDS & abx if indicated

33
Q

should you give a horse with a melting ulcer topical steroids? why?

A

NO!!! will increase melting ulcers!!!!

34
Q

what clinical signs are associated with complex ulcers in horses?

A

painful!!! scleral injectiom, melting ulcers, & corneal neovascularization

35
Q

what follow up is indicated for horses with complex corneal ulcers?

A

recheck them in 1-2 days, then 1-2 weeks, & then 4-8 weeks

36
Q

when would you do surgery for a complex corneal ulcer? what is the goal of surgical therapy for a horse with a complex corneal ulcer?

A

50% stromal depth, rapidly progressive, melting ulcers with no vascular response that has perforated

goal - preserve the globe, vision, & cosmetics

do conjunctival graft or enucleation

37
Q

what lesion is shown in this photo? what causes it?

A

corneal stromal abscess

small puncture wounds leave infection or foreign bodies in the cornea without an ulcer

caused by bacterial/fungal infections

38
Q

what clinical signs are seen with corneal stromal abscesses?

A

blepharospasm, corneal stromal infiltrate, corneal edema, neovascularization, reflex uveitis, & miosis

39
Q

what is the therapy recommended for corneal stromal ulcers?

A

medical therapy is identical to what you would do for an infected corneal ulcer, but you must increase the frequency due to the intact corneal epithelium

anti-melting medication is not indicated!

40
Q

what are your surgical options for treating a corneal stromal abscess?

A

intrastromal voriconazole injection

penetrating keratoplasty - resection of the cornea & diseased tissue is replaced with collagen matrix or donor cornea

posterior lamellar keratoplasty - resect abscessed tissue & replace the defect with a donor cornea

deep lamellar endothelial keratoplasty - corneal incision is made over the limbus, the defect is removed, & then replaced

enucleation

41
Q

what does an owner need to know if their horse has a corneal infection?

A

corneal infections take a long time to treat & are expensive!!!

42
Q

what lesion is shown in the photo? what clinical signs are seen?

A

indolent corneal ulcer - ulcer that lasts longer than 1-2 weeks with no reason for delayed healing that is common in older horses due to decreased corneal sensitivity

superficial corneal ulcer with loose edges of non-adherent corneal epithelium, reflex uveitis may be present, no visible signs of inflammation

43
Q

what is the gold standard treatment for indolent ulcers? what other procedures are options for treating them?

A

diamond burr debridement

focal thermokeratoplasty - high success rate with more scar tissue

superficial keratectomy - high success rate with scar tissue & expensive

44
Q

what treatments, other than surgery, are used for treating indolent ulcers in horses?

A

abx, atropine, systemic NSAID, topical antifungals, & protective fly mask

45
Q

what follow up is indicated for a horse with an indolent ulcer?

A

recheck in 3-4 weeks - takes 1-3 months to heal!!!

may need repeated surgical procedures

46
Q

T/F: in horses with indolent ulcers, the other eye is predisposed to developing the same lesion

A

true

47
Q

what is immune-mediated keratitis?

A

non-ulcerative keratitis that causes corneal opacity, vascularization, & variable degrees of pain

48
Q

what is the lesion shown in the photo?

A

immune mediated keratitis

49
Q

what are the 4 different categories of immune mediated keratitis?

A
  1. epithelial - multifocal punctate opacities seen in the ventral aspect of the cornea, LEAST COMMON
  2. superficial stroma - waxing & waning corneal opacity, white to yellow infiltrate, surrounded by neovascularization
  3. mid-stromal - denser than superficial, waxing & waning corneal opacity, surrounded by deep & straight vascularization
  4. endothelial - chronic, slowly progressive, dark cellular infiltrate, minimal neovascularization, & the development of bullous keratopathy
50
Q

how is immune mediate keratitis diagnosed?

A

response to treatment, histopathology (t-cell population, stromal necrosis, & no infectious organisms)

51
Q

what treatment is indicated for immune mediated keratitis? what follow up plan is indicated?

A

topical NSAIDS, steroids, & immunomodulators

success depends on the type of immune-mediated keratitis (lifelong therapy is indicated)

flare ups will occur - clients may prefer surgery

recheck 2-4 weeks after starting therapy

52
Q

what surgical procedure can be done for a horse with immune mediated keratitis?

A

superficial keratectomy or episcleral cyclosporine implant

53
Q

what herpes viruses cause EHV keratitis corneal pathology?

A

EHV-2 & EHV-5

54
Q

what lesion is shown in the photo? what clinical signs are seen?

A

EHV keratitis - linear to punctate superficial to sub-epithelial infiltrate!!!

corneal edema, blepharospasm, tearing, mucopurulent discharge

55
Q

how is EHV keratitis diagnosed?

A

PCR & ruling out infectious diseases

56
Q

how is EHV keratitis treated? what follow up is indicated?

A

topical antiviral & systemic NSAIDS

recheck in 3-4 weeks - can develop flares in a time of stress (showing, shipping, etc)

57
Q

what lesion is shown in this photo? what clinical signs are seen?

A

subepithelial keratomycosis - microerosions induced by commensal fungus that is nearly identical to presentation of immune mediated keratitis & EHV keratitis

but pain is worse in subepithelial keratomycosis!!!!

58
Q

how is subepithelial keratomycosis diagnosed? how is it treated? what follow up is indicated?

A

corneal cytology, culture, & fungal PCR

topical atropine, antifungal, abx, & systemic NSAIDS

recheck in 2 weeks, & then recheck every 2-4 weeks until it is healed (takes 5-6 weeks)

59
Q

what is the most common ocular tumor in the horse?

A

squamous cell carcinoma - locally aggressive & slow to metastasize

recurrence is common

60
Q

what lesion is show in this photo?

A

ocular squamous cell carcinoma

61
Q

what risk factors are associated with ocular squamous cell carcinomas in horses?

A

lack of pigment, older horses, breeds (appaloosa, haflinger, draft) genetics (DDB2 protein), UV radiation, & chronic tissue irritation

62
Q

what is the location distribution seen in ocular squamous cell carcinomas?

A

28% 3rd eyelid

28% limbus

23% lower eyelid

21% cornea/conjunctiva/orbit

63
Q

what differentials do you have for ocular squamous cell carcinomas in horses?

A

neoplasia, inflammation, & parasites

64
Q

how is an ocular squamous cell carcinoma diagnosed?

A

biopsy!!!

65
Q

what treatment is used for equine ocular squamous cell carcinomas?

A

chemo + sx therapy + adjunctive therapy (must enucleate the eye to get wide margins!!!)

chemo is effective for small/superficial lesions, but it is a long treatment course & it is irritating

cryotherapy used for large lesions - good prognosis & relatively safe

66
Q

what clinical signs are seen in horses with ocular squamous cell carcinomas?

A

ocular discharge, hyperemia, thickened cornea/conjunctiva with cobblestone-like texture

67
Q

what post-op treatment is needed for ocular SCC?

A

topical atropine, abx, & systemic NSAIDS

68
Q

what recheck plan is indicated for ocular SCC?

A

recheck in 2 weeks then every 2-4 weeks until healed then every 6-12 months for life - recurrence rate is high!!!

69
Q

what treatment option is the best prognosis for equine ocular SCC?

A

surgery + irradiation = 65-100%

70
Q

what are some poor prognostic indicators of equine ocular SCC?

A

increased lesion size, orbital extension, recurrence

owner compliance is vital!!!! UV fly masks are great to prevent!!!

LA DX & TX II (44 decks)

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