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SA DX & TX II > Final Exam - Cornea > Flashcards

Final Exam - Cornea Flashcards

1
Q

what is ciliary flush (neovascularization)?

A

360° degree deep corneal neovascularization that is pathognomonic for uveitis - these vessels arise in the cornea from an intraocular or deep origin

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2
Q

what is corneal edema?

A

only blue opacity!!! appears heterogenous or fluffy

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3
Q

what are the only 2 mechanisms that cause corneal edema?

A

epithelial disruption or endothelial disruption

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4
Q

if you see focal edema as a part of corneal edema, what conditions should you think of?

A

superficial ulcers, anterior lens luxations, & early corneal endothelial dystrophy

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5
Q

if you see diffuse edema as a part of corneal edema, what conditions should you consider?

A

think of glaucoma, stromal ulcers, uveitis, endothelial degeneration, or advanced endothelial dystrophy

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6
Q

if you see bullous keratopathy as a part of corneal edema, what conditions should you think of?

A

diffuse edema that is chronic & severe that can supersaturate the corneal stroma causing sub-epithelial blisters to develop (ulcers frequently occur spontaneously)

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7
Q

what is corneal fibrosis?

A

corneal scarring - results from stromal collagen contracture & appears as a dull/wispy white, may see ghost vessels from past keratitis, non-painful condition

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8
Q

what is corneal dystrophy/degeneration?

A

dystrophy most often involving corneal lipids & appears glittery/shiny appears glittery/shiny with degeneration most often involving calcium & appears gritty/chalky - calcific degeneration more often associated with ulceration & pain

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9
Q

what is a descemetocele?

A

stromal ulcer that reaches the depth of descemet’s membrane where corneal epithelium & stroma are lost

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10
Q

what is deep corneal vascularization?

A

vessel pattern that occurs in response to deep disease processes (deep/infected ulcers & uveitis) - these vessels are usually straight, can’t be seen crossing the limbus, & don’t extend as far across the cornea as superficial neovascularization

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11
Q

what is a facet?

A

loss of corneal stroma with intact overlying epithelium, non-staining depression in the cornea - occurs because epithelialization progresses more rapidly than a stromal healing

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12
Q

what is feline corneal sequestrum?

A

unknown cause of brown or black discoloration - condition results from chronic corneal irritation and/or ulceration

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13
Q

what is the most common cause of feline corneal ulceration?

A

feline herpesvirus

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14
Q

what is hypopyon?

A

sterile white blood cell inflammatory reaction within the eye that often settles within the ventral anterior chamber with gravity

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15
Q

what does it mean if hypopyon is present alongside a corneal ulcer?

A

indicates stromal involvement & infection - emergency!!!

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16
Q

what is keratitis?

A

inflammation of the cornea

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17
Q

what are keratic precipitates?

A

cellular adhesions to the endothelium that are pathognomic for uveitis that have a classic appearance that is easily recognized with tiny dots from the mid-portion of the cornea that become larger & denser in the ventral cornea

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18
Q

what is keratomalacia?

A

corneal melting/melting ulcer/collagenolysis - bacterial/fungal/white blood cell associated enzymatic dissolution of the corneal stroma leading to a creamy, softened appearance to the corneal stroma - medical emergency

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19
Q

what is the limbus?

A

360° junction between the cornea & sclera/conjunctiva which is the migratory starting point for wound healing & many corneal pathologies - deep to the limbus, the cornea is at its closest point to the uvea (iris) also the site of epithelial stem cells, new blood vessels, & pigment

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20
Q

what is reflex uveitis?

A

uveitis that is triggered by corneal ulceration specifically - infected ulcers trigger severe reflexive uveitis where as non-infected ulcers trigger mild reflexive uveitis - used to distinguish non-emergent from emergent!!

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21
Q

what does the superficial cornea refer to?

A

pre-corneal tear film & epithelium, so superficial ulcer indicates a loss of epithelium only (important distinction from stromal qualifier)

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22
Q

what is superficial corneal neovascularization?

A

vessel pattern seen in superficial disease processes - think of KCS, eyelid disorders, feline herpes, & superficial corneal ulcers - vessels are tree like in appearance & can often be seen crossing the limbus with active vessels fully perfused indicating active/poorly controlled inflammation

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23
Q

what does stromal refer to in regards to the cornea?

A

entire corneal stroma - loss of stroma and/or presence of white blood cell stromal infiltration is often painful & signals infection - medical emergency!!!

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24
Q

what is white blood cell corneal infiltrate?

A

white category of corneal opacity that is a sign of active inflammation (keratitis) that is often painful & signals infection with its presence indicating an emergency

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25
Q

what do white blood cell corneal infiltrates look like?

A

green in appearance & most commonly observed in equine stromal abscesses & cases of corneal melting (keratomalacia)

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26
Q

what are the 4 primary layers of the cornea?

A
  1. epithelium - hydrophobic, repels fluorescein 2. stroma - hydrophilic, retains fluorescein 3. descemet’s membrane - hydrophobic, repels fluorescein 4. endothelium - not involved in fluorescein staining
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27
Q

what qualifies superficial & deep lesions in the cornea?

A

superficial - epithelial disruption, less emergent deep - stromal disruption/infiltration, always emergent!!!!!

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28
Q

which one represents a surgical emergency, medical emergency, & medical/surgical emergency?

A

left - surgical emergency, discuss referral

middle - medical emergency, high frequency treatment

right - medical/surgical emergency, discuss referral

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29
Q

what are the 4 contributing factors of how the cornea stays clear?

A
  1. avascular (in health - vessels only appear with inflammation) 2. non-myelinated nerves, densest network of nociceptive nerve fibers in the body located deep to the corneal epithelium 3. dehydrated - epithelium is the barrier to the tear film while endothelium has the active pump & barrier to aqueous humor 4. ordered cell arrangement that allows complete transmittance of light (in health)
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30
Q

what is the reason for why we can appreciate corneal opacities?

A

disruptions to the ordered cell arrangement reflects, scatters, or absorbs light

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31
Q

how does the epithelium heal in superficial corneal ulcers?

A
  1. epithelial breach is very painful!!! stroma will take up fluorescein at diagnosis 2. hemidesmosomes degrade & the epithelium is set up to slide & rapid cell division occurs at the limbus 3. epithelium slides over the ulcer 4. fluorescein stain is no longer taken up & the animal is comfortable 5. epithelium anchors itself to the stroma via hemidesmosomes & an indolent ulcer is avoided!
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32
Q

how long does it take for a superficial ulcer to heal?

A

7 days or less even with complete epithelial loss

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33
Q

how does the stroma heal for deep corneal ulcers?

A
  1. stromal cells (keratocytes) transform into contractile cells 2. these cells fill the defects 3. ulcer then epithelializes 4. stromal contracture causes disorganized of the ordered collagen resulting in a scar that we call corneal fibrosis
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34
Q

how long does it take for a stromal ulcer to heal?

A

days to weeks

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35
Q

what causes the development of a facet?

A

often, the epithelium slides over the remodeled stroma efore it becomes level with the surrounding epithelium - so facets, are indicative or previous deep/stromal corneal ulcers that are generally associated with comfort!!!!

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36
Q

how does a descemetocele heal?

A

limited & very slow (takes weeks to months) - vision threatening complications are likely with medical management!!!! surgical referral should be discussed!

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37
Q

epithelial barrier disruption is more likely to cause what corneal opacity?

A

blue corneal opacity - focal edema

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38
Q

endothelial barrier/pump dysfunction is more likely to cause what corneal opacity?

A

blue corneal opacity - diffuse edema

glaucoma, stromal ulcers, uveitis, endothelial degeneration/dystrophy, chronic/severe = bullous keratopathy

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39
Q

what causes should you consider if you see focal edema causing blue corneal opacity?

A

superficial ulcers, anterior lens luxations, & endothelial dystrophy

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40
Q

what causes should you consider if you see diffuse edema causing blue corneal opacity?

A

glaucoma, stromal ulcers, uveitis, endothelial degeneration, or endothelial dystrophy (advanced), & chronic & severe (bullous keratopathy)

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41
Q

if there is a blue opacity of the cornea, what does that mean?

A

edema!!!

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42
Q

what is the most common cause of focal corneal edema in dogs?

A

anterior lens luxations - progresses lateral to medial

43
Q

what dog breeds are do we presume inheritance for focal edema from endothelial dystrophy?

A

chihuahuas, dachshund, & GSP

44
Q

what are some examples of diseases that will cause diffuse corneal edema due to reduction in endothelial cell number & function?

A
  1. glaucoma (primary/inherited)
  2. stromal ulcer + reflex uveitis
  3. uveitis
  4. advanced endothelial dystrophy
45
Q

what is the sequelae of diffuse corneal edema that is chronic & severe?

A

can lead to bullous keratopathy - spontaneous corneal ulceration ensures

46
Q

what is the one cause with 2 important sources for red corneal opacity?

A

vessels

  1. superficial neovascularization - active, granulation tissue, inactive, or ghost vessels
  2. deep neovascularization - ciliary flush if 360°
47
Q

what is the pattern significance of superficial corneal neovascularization?

A

stages of activity provide us a disease timeline

pathway of superficial vessels often points to the origin of inflammation

48
Q

what causes superficial corneal neovascularization? how long does it take for superficial neovascularization to start? how much does it grow a day?

A

causes - think of superficial stimuli (adnexal diseases such as distichia, entropion, lagophthalmos, etc. & ocular surface disorders such as KCS, SF corneal ulcers, pannus, etc)

takes ~3 days from the insult to see vessels growing
progress 1mm/day

49
Q

T/F: vessels that cross the limbus are a common feature of superficial neovascularization that is not found in deep neovascularization

A

true

50
Q

what is seen on these eyes that is a feature of superficial neovascularization of the cornea?

A

granulation tissue

51
Q

what is the difference between inactive & ghost vessels?

A

inactive - perfused, but regressing vessels

ghost vessels - non-perfused/empty vessels

52
Q

what are the 2 most common causes of deep neovascularization?

A

uveitis

deep corneal ulceration (+/- reflex uveitis)

53
Q

what is ciliary flush? what disease does it only occur in?

A

360° deep neovascularization - seen only with deep neovascularization

54
Q

what is the timeline for development of deep vascularization?

A

~3 days from the insult to start growing vessels

progress is slower than superficial vessels

55
Q

what kind of vascularization is shown here?

A

deep neovascularization - crown of thorns

56
Q

what are the 3 variations of white corneal opacities?

A
  1. white with yellow or green hue - white blood cell infiltration
  2. white with gray or whispy features - fibrosis
  3. crystalline or chalky white - mineral or lipid due to dystrophy or degeneration
57
Q

the _______ part of the cornea is most susceptible to degradation

A

stroma

58
Q

to identify the basic pathologic changes of the cornea, what feature are you looking at?

A

the color change!!!

59
Q

what does a blue color change of the cornea signify?

A

edema is the underlying pathology

60
Q

what does a red color change of the cornea signify?

A

neovascularization is occurring - consider superficial or deep

61
Q

what does a white color change of the cornea signify?

A

corneal dystrophy - lipid, non-painful, common in dogs

corneal degeneration - ulcerates, primary corneal disease or systemic, acquired

62
Q

what does a brown/black color change of the cornea signify?

A

melanin - either epithelial (chronic ocular surface irritation) or endothelial (thick, uveal cysts or iris tissue endothelial adhesion)

feline corneal sequestrum - chronic ocular surface irritation such as herpes

63
Q

what does a tan or greasy punctate color change of the cornea signify?

A

keratin precipitates, cellular & fibrinous adhesions to the endothelial surface (uveitis) - ventral, big dots on bottom & small dots on top

64
Q

what factors make brachycephalic breeds more likely to experience corneal ulceration?

A
  1. ocular prominence
  2. decreased corneal sensitivity
  3. eyelid abnormalities
  4. KCS predisposition
65
Q

how should an e-collar be constructed for a dog with ulcerative keratitis?

A

need it to extend just beyond the nose when pushed back to the shoulders & be firm

66
Q

what are some causes of simple superficial corneal ulcers? how long does it take to heal?

A

causes - eyelid/hair irritant, lagophthalmos, KCS, trauma, & herpes in cats

no complicating factors - should heal in 5-7 days

67
Q

what does SCCED mean?

A

spontaneous chronic corneal epithelial defect - indolent ulcer

68
Q

what dogs are predisposed to getting indolent ulcers?

A

middle aged boxers

69
Q

in order of most toxic to least toxic, what drugs should be avoided for animals with corneal ulceration? why?

A

proparacaine - okay to use in exam room!!!!
NeoPolyDex ointment/suspension
prednisolone
diclofenac (nsaid)
flurbiprofen (nsaid)

all of these meds will delay healing & enhance corneal destruction!!!

70
Q

why do we need to make empiric selections for drugs for stromal ulcers of the cornea?

A

the stroma is very susceptible to rapid & complete destruction (<24 hours) following the establishment of a bacterial infection - can’t wait for cytology/culture to direct targeted therapies

71
Q

what guidelines should you follow for empiric selections for antibiotics for corneal ulcers?

A

superficial - prophylactic abx selection & frequency

stromal - rescue abx & frequencies

breed considerations - stromal ulceration is 10X more likely in a small brachycephalic breed relative to larger breeds

72
Q

what is the definition of a prophylactic antibiotic for a superficial corneal ulcer? what frequency should be used?

A

broad spectrum abx that is intended to stop the proliferation of a normal ocular surface bacteria within the stroma of a superficial corneal ulcer

TID to QID - never less than 3X daily due to 1st order pharmokinetics & resistance concerns

73
Q

what are your prophylactic abx options for superficial corneal ulcers?

A

all available as antibiotic ointments & solutions

erythromycin - well tolerated in cats

polymixin b oxytetracycline - terramycin

NeoPolyBac

NeoPolyGram

74
Q

what 2 factors qualify a drug as a rescue antibiotic for deep corneal ulcers?

A
  1. abx that has historically demonstrated efficacy against the most common bacterial isolates from stromal ulcers
  2. abx that has a high degree of ocular penetration
75
Q

what is the rescue frequency for abx for stromal ulcers?

A

6x daily during waking hours for outpatients

12-24X daily for hospitalized cases

76
Q

what clinical assumption are you making when choosing rescue frequencies & selections for a corneal ulcer?

A

assuming the ulcer is stromal and/or at high risk to become stromal - examples of KCS & small brachycephalic patients!!!

77
Q

what are your single drop rescue options for stromal ulcers? what are your two drop rescue options for stromal ulcers?

A

4th generation fluoroquinolones - moxifloxacin or gatifloxacin ophthalmic solution (convenience option)

2nd generation fluoroquinolones + topical cephalosporin - olfoxacin, ciprofloxacin, & 5% compounded cefazolin

78
Q

what are the 3 possibilities for complex superficial ulcers?

A
  1. indolent ulcer - SCCED, most common
  2. persistent irritant
  3. early/insidious stromal ulcer
79
Q

what is the pathology of dogs with indolent ulcers due to SCCED?

A

healing is altered because there is lack of epithelial adherence to the stroma

80
Q

how do you diagnose an indolent ulcer?

A

test the epithelium with a q-tip - normal epithelium will not debride easily!!!!!

81
Q

this is the classic staining pattern of what type of ulcer?

A

complex indolent corneal ulceration

82
Q

what are the 2 important distinctions of therapy for complex indolent superficial corneal ulcers?

A
  1. healing depends on the mechanical debridement of the ulcer!!!!
    q-tip debridement - 50% healed at 2-3 weeks
    diamond burr - 80-90% healed at 2-3 weeks
  2. follow up recommendations - recheck weekly & DO NOT REPEAT DEBRIDEMENT IF <14 DAYS FROM THE PREVIOUS DEBRIDEMENT!!!!!
83
Q

what are the criteria for using a diamond burr for debridement of an indolent ulcer?

A

performed following proparacaine & CTA debridement

never <3.5mm tip

never >60 seconds

never for stromal ulcers!!!!!

84
Q

what are the moderate to severe clinical signs associated with reflex uveitis?

A

miosis, aqueous flare, diffuse corneal edema, hypopyon/hyphema

85
Q

what are the 3 most common bacterias that cause stromal ulcers?

A

staph spp - gram positive aerobic cocci
strep spp - gram positive aerobic cocci
pseudomonas aeruginosa - gram negative facultative anaerobic rod

86
Q

what bacteria most commonly causes melting ulcers?

A

pseudomonas aeruginosa - gram negative facultative anaerobic rod

87
Q

what is collagenolysis?

A

enzymatic destruction of corneal collagen

88
Q

what is keratomalacia?

A

softening/melting of the corneal stroma due to collagenolysis from bacteria/fungi & neutrophil enzymes

89
Q

what are the identifying features of stromal ulcerations?

A

inappropriate level of reflex uveitis, severe corneal edema, white blood cell infiltration, deep corneal vessels & episcleral injection, visible stromal loss/disruption, & malacia

90
Q

T/F: in general, if you can see an ulcer with your naked eye, it is highly concerning for a deep, infected corneal ulcer

A

true

91
Q

what is pictured here?

A

keratomalacia - cornea is softening

92
Q

what are some supporting clinical signs for corneal perforation?

A

positive seidel test - active leaking
wrinkled corneal appearance, shallow anterior chamber, iris prolapse, fibrin plug, hyphema

93
Q

what is the minimum diagnostic assessment that should be done for stromal ulcers?

A

stromal ulcers should be sampled cytologically & cultured anaerobically following instillation of proparacaine

cytology for empiric selection & culture to guide abx changes at follow-up

94
Q

when should you add systemic abx for a patient with a stromal ulcer?

A
  1. ulcer has become vascularized
  2. cornea is close to perforation or has perforated
  3. iatrogenic vascularization
95
Q

when do you offer referral for surgical repair for a stromal ulcer?

A
  1. 50% of greater depth & perforations
  2. cases that fail to improve at the first follow-up exam where rescue therapies are already being used
96
Q

what is the most common surgical repair done on the cornea for stromal ulcers?

A

conjunctival pedicle flap procedure

97
Q

what breeds are predisposed to pannus?

A

shepherds, shepherd crosses, & greyhounds

increased incidence in high altitudes & low latitude (increased UV light)

98
Q

what is pannus?

A

immune mediated reaction to the epithelial surface (cornea & conjunctiva) that is non-painful but can be blinding!

99
Q

what is seen on cytology that is supportive of pannus?

A

lymphocytes & plasma cells, blood vessels (granulation tissue), & pigment

100
Q

what are the 2 categories that we split pannus in to?

A
  1. typical - corneal conjunctival origin
  2. atypical - third eyelid origin
101
Q

what disease is shown here?

A

typical pannus (chronic superficial keratitis)

102
Q

what is the treatment for pannus?

A

topical anti-inflammatory therapy - short term steroids or long term topical cyclosporine

UV light avoidance or protection

103
Q

T/F: pannus is an example of a non-ulcerative keratitis

A

true

SA DX & TX II (62 decks)

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