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RUSVM SAM 2 > Cornea > Flashcards

Cornea Flashcards

1
Q

What are the 4 layers of the cornea?

A

Epithelium
Stroma
Descemets membrane
Endothelium

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2
Q

How does the cornea stay clear?

A 
Avascular 
Non-myelinated nerves 
Dehydrated 
- epithelium (barrier to tear film) 
-endothelium (active pump and barrier to aqueous humor) 
Ordered cell arrangement
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3
Q

How does the epithelium heal?

A

Epithelialization

Hemidesomosmes dreate
Epithelium set up to slide
Rapid cell division from the limbus—> slide to cover the ulcer
Epithelium becomes fixed to stroma as hemidesmososmes form

Takes 7 days to complete

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4
Q

How does a stromal ulcer heal?

A

Stromal cells (keratocytes) transform into contractile cells

Cells fill the defect

Ulcer then ‘epithelializes’

Stromal contracture causes disorganization of the ordered collagen, resulting in scar

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5
Q

What do you call a non—staining depression of the cornea?

A

Facet

— occurs when epithelium slides over remodeled stroma before it has become level with the surrounding epithelium

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6
Q

How does a descemetocele heal?

A

Vascular ingrowth = takes a long time

Scar formation (takes weeks to months)

Eventually the ulcer will re-epithelialize

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7
Q

Blue corneal opacity is caused by?

A

Edema

— epithelial or endothelial barrier disruption

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8
Q

Degree of corneal edema depends on what factors ?

A

Geographic size of the ulcer

Depth of ulcer

Reflex uveitis is present or not

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9
Q

What are causes of a generalized reduced function of the corneal endothelial barrier, resulting in a generalized edema?

A

Glaucoma

Uveitis

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10
Q

Red corneal opacity indicated?

A

Corneal neovascularization (can be superficial or deep)

Superficial —> granulation tissue and ghost vessels

Deep —> ciliary flush

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11
Q

What stimuli can induce superficial neovascularization?

A

KCS
Eyelid conformation
Hair abnormalities (entropion, distichia, trichiasis)

-> vessels move toward the offending stimulus

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12
Q

What do you call a dense, raised collection of superficial vessels on the cornea due to a chronic stimuli?

A

Granulation tissue

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13
Q

What are ghost vessels?

A

Non-perfused, empty vessels

Occurs when the stimulus/irritant has been removed (eg when a corneal ulcer)

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14
Q

What stimuli can cause a deep neovascularization ?

A

Uvititis
Glaucoma
Deep corneal inflammation/ulceration

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15
Q

What are causes of a white with yellow/green corneal opacity?

A

White blood cell infiltration

Eg deep stromal abscess or hypopyon due to reflex uveitis

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16
Q

What are causes of a white withe gray/wispy cornea?

A

Fibrosis

Eg dogs with healed corneal ulcer

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17
Q

What are causes of a crystalline or chalky white corneal opacity?

A

Mineral or lipid

  • dystrophy
  • degeneration
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18
Q

“Sparkly” opacities to the cornea are due to?

A

Corneal dystrophy = lipid deposits

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19
Q

T/F: corneal degeneration can be lipid or mineral deposits and often ulcerated

A

True

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20
Q

A disrupted specular reflection indicates??

A

Irregularity of the ocular surface

21
Q

Brown opacities of the corneum?

A

Epithelial
— pigmentary keratitis (melanin)

Endothelial
— deflated uveal cysts
—anterior synechia from previous corneal perforation and iris prolapse

22
Q

Black opacity in corneum of feline?

A

Feline corneal sequestrum
— necrotic corneal stroma

Occurs after chronic corneal ulceration often due to FHV1

23
Q

You see tan/greasy punctuate in the cornea. What is this?

A

Keratoconjunctivitis precipitates — cellular and fibrinous adhesions to endothelial surface

Usually settles in the ventral corneal

24
Q

What are 4 risk factors that predispose brachycephalic to corneal ulcers?

A

Ocular prominence

Decreased corneal sensitivity

Adnexal abnormalities (eg nasal fold trichiasis or lagopthalmos)

Tear film abnormalities

25
T/F: all animals with corneal ulcers should be treated with topical steroids and placed in an Ecollar
FALSE ``` NEVER give steroids to ulcer patients Cause -> delayed healing -> more corneal destruction -> increased risk of infection ``` But the E collar is a good thing
26
Loss of epithelium with no stromal loss is called?
Superficial corneal ulceration
27
What are causes of superficial corneal ulceration?
Irritants - adnexal abnormalities - tear film abnormalities - foreign bodies Infection -herpesvirus Trauma
28
What are the two classification of superficial corneal ulcers?
Uncomplicated/ simple — heals in 7 days for less by epithelialization Complicated/complex — an ulcer that does not heal appropriately
29
What is the treatment for an uncomplicated superficial ulcer?
Ecollar Broad spectrum antibiotics for 3-4x/day +/- atropine Recheck in 5-days
30
What are the types of complicated superficial ulcers?
Indolent Persistent irritant Infeciton
31
What is the signalment for indolent ulcers?
Middle aged and older dogs | Boxers!
32
Why do indolent ulcers develop?
Initial corneal injury with altered healing due to lack of adherence of epithelium to stroma (abnormal hemidesmosomes)
33
How can you test for indolent ulcers?
Test epithelium with cotton tipped applicator - normal epithelium will not debride easily Fluorescin halo — staining beyond epithelial ulcer margins
34
What is the treatment for indolent ulcers?
Debridement with sterile q-tip 50% will heal in 2weeks ``` If not healed in 2 weeks... Anterior stromal puncture OR Diamond burr debridement (These should never be not on infected ulcers!) ``` Topical treatment similar to superficial ulcers - antibiotics - +/- atropine - +/- pain managment (NSAID or tramadol)
35
What is the most common cause of an infected superficial ulcer in cats?
Herpesvirus
36
T/F: most deep stromal corneal ulcers are considered complex, most are caused by infection
True
37
What is the pathogenesis of deep corneal ulcers?
Most due to infection (bacterial or fungal) Collagenolysis — enzymatic destruction of corneal collagen -> keratomalacia = softening of the corneal stroma due to collagenolysis
38
What are the most common bacteria causing deep corneal ulcers?
Staphylococcus spp Streptococcus spp Pseudomonas aeruginosa (most common cause of melting)
39
What is a reflex uveitis?
Ulcerative keratitis causing varying degrees of uveitis Ophthalmic branch of CN V innervates both the cornea and uvea Corneal irritation stimulates corneal nerves and also sends noxious stimuli back to the ciliary body -> release of inflammatory medications and breakdown of blood ocular barrier
40
Clinical signs of a uveitis?
Episceral injection Diffuse corneal edema Severe miosis Turbid anterior chamber = aqueous flare
41
Why do we commonly see descemetoceles more commonly than deep corneal ulcers?
Loss of epithelium —> stoma extremely sensitive to proteases from fungi and bacteria Progression of collagenolysis through the stroma is rapid Descemets membranes is moderately resistant to these proteases
42
What clinical signs do you see with corneal perforation?
``` Wrinkled corneal appearance Shallow anterior chamber Iris prolapse Fibrin plug Hyphema ``` Positive Seidel test — active leaking
43
What diagnostics should you do in a case of deep stromal ulceration?
Schirmer tear test — more important in normal eye Fluorescien Topical anesthesia Cytology —> guides initial therapy Aerobic culture —> changes to therapy Tonometry (avoid in fragile eyes)
44
What can you use to help in an ocular exam in a patient with a painful corneal ulcer?
Proparacaine NEVER send home with client — repeated used is toxic to corneal and may result in melting corneal ulcer
45
When is surgery indicated in a patient with deep corneal ulcers?
When there is >50% stromal loss — conjunctival pedicle flap — 360 conjunctival flap
46
What are advantages and disadvantages of conjunctival pedicle flaps?
Provides immediate tectonic strength Provides a blood supply for paternal antibiotic augmentation Provides serum for anti-collagenolysis Disadvantages— can cover visual axis
47
What is the protocol for medically treating deep corneal ulcers?
Topical antibiotics (4quadrant coverage) - cephalosporins — gram positive and anaerobes - fluoroquinolones or aminoglycosides — gram negatives and aerobes Every 1-2hours for the first 2days ``` Systemic antibiotics (sometimes) Anticollagenase therapy (melting ulcers) Reflex uveitis and pain managing (atropine, NSAID/tramadol) ```
48
What are the indications for systemic antibiotics with corneal ulcers?
The ulcer is well vascularized Cornea has perforated Conjunctival flap was performed
49
What products can you use for anticollagenase therapy to treat a melting ulcer?
Autologous serum EDTA N-acetylcystine

RUSVM SAM 2 (44 decks)

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