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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
Q

T/F: all animals with corneal ulcers should be treated with topical steroids and placed in an Ecollar

A

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
Q

Loss of epithelium with no stromal loss is called?

A

Superficial corneal ulceration

27
Q

What are causes of superficial corneal ulceration?

A

Irritants

  • adnexal abnormalities
  • tear film abnormalities
  • foreign bodies

Infection
-herpesvirus

Trauma

28
Q

What are the two classification of superficial corneal ulcers?

A

Uncomplicated/ simple — heals in 7 days for less by epithelialization

Complicated/complex — an ulcer that does not heal appropriately

29
Q

What is the treatment for an uncomplicated superficial ulcer?

A

Ecollar

Broad spectrum antibiotics for 3-4x/day

+/- atropine

Recheck in 5-days

30
Q

What are the types of complicated superficial ulcers?

A

Indolent

Persistent irritant

Infeciton

31
Q

What is the signalment for indolent ulcers?

A

Middle aged and older dogs

Boxers!

32
Q

Why do indolent ulcers develop?

A

Initial corneal injury with altered healing due to lack of adherence of epithelium to stroma (abnormal hemidesmosomes)

33
Q

How can you test for indolent ulcers?

A

Test epithelium with cotton tipped applicator
- normal epithelium will not debride easily

Fluorescin halo — staining beyond epithelial ulcer margins

34
Q

What is the treatment for indolent ulcers?

A

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
Q

What is the most common cause of an infected superficial ulcer in cats?

A

Herpesvirus

36
Q

T/F: most deep stromal corneal ulcers are considered complex, most are caused by infection

A

True

37
Q

What is the pathogenesis of deep corneal ulcers?

A

Most due to infection (bacterial or fungal)

Collagenolysis — enzymatic destruction of corneal collagen
-> keratomalacia = softening of the corneal stroma due to collagenolysis

38
Q

What are the most common bacteria causing deep corneal ulcers?

A

Staphylococcus spp
Streptococcus spp
Pseudomonas aeruginosa (most common cause of melting)

39
Q

What is a reflex uveitis?

A

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
Q

Clinical signs of a uveitis?

A

Episceral injection
Diffuse corneal edema
Severe miosis
Turbid anterior chamber = aqueous flare

41
Q

Why do we commonly see descemetoceles more commonly than deep corneal ulcers?

A

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
Q

What clinical signs do you see with corneal perforation?

A 
Wrinkled corneal appearance 
Shallow anterior chamber 
Iris prolapse 
Fibrin plug 
Hyphema

Positive Seidel test — active leaking

43
Q

What diagnostics should you do in a case of deep stromal ulceration?

A

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
Q

What can you use to help in an ocular exam in a patient with a painful corneal ulcer?

A

Proparacaine

NEVER send home with client — repeated used is toxic to corneal and may result in melting corneal ulcer

45
Q

When is surgery indicated in a patient with deep corneal ulcers?

A

When there is >50% stromal loss

— conjunctival pedicle flap
— 360 conjunctival flap

46
Q

What are advantages and disadvantages of conjunctival pedicle flaps?

A

Provides immediate tectonic strength

Provides a blood supply for paternal antibiotic augmentation

Provides serum for anti-collagenolysis

Disadvantages— can cover visual axis

47
Q

What is the protocol for medically treating deep corneal ulcers?

A

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
Q

What are the indications for systemic antibiotics with corneal ulcers?

A

The ulcer is well vascularized
Cornea has perforated
Conjunctival flap was performed

49
Q

What products can you use for anticollagenase therapy to treat a melting ulcer?

A

Autologous serum

EDTA

N-acetylcystine

RUSVM SAM 2 (44 decks)

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