Cornea Flashcards Preview

RUSVM SAM 2 > Cornea > Flashcards

Flashcards in Cornea Deck (49):
1

What are the 4 layers of the cornea?

Epithelium
Stroma
Descemets membrane
Endothelium

2

How does the cornea stay clear?

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

3

How does the epithelium heal?

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

4

How does a stromal ulcer heal?

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

5

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

Facet

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

6

How does a descemetocele heal?

Vascular ingrowth = takes a long time

Scar formation (takes weeks to months)

Eventually the ulcer will re-epithelialize

7

Blue corneal opacity is caused by?

Edema
— epithelial or endothelial barrier disruption

8

Degree of corneal edema depends on what factors ?

Geographic size of the ulcer

Depth of ulcer

Reflex uveitis is present or not

9

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

Glaucoma

Uveitis

10

Red corneal opacity indicated?

Corneal neovascularization (can be superficial or deep)

Superficial —> granulation tissue and ghost vessels

Deep —> ciliary flush

11

What stimuli can induce superficial neovascularization?

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

-> vessels move toward the offending stimulus

12

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

Granulation tissue

13

What are ghost vessels?

Non-perfused, empty vessels

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

14

What stimuli can cause a deep neovascularization ?

Uvititis
Glaucoma
Deep corneal inflammation/ulceration

15

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

White blood cell infiltration

(Eg deep stromal abscess or hypopyon due to reflex uveitis)

16

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

Fibrosis

(Eg dogs with healed corneal ulcer)

17

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

Mineral or lipid
-dystrophy
-degeneration

18

“Sparkly” opacities to the cornea are due to?

Corneal dystrophy = lipid deposits

19

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

True

20

A disrupted specular reflection indicates??

Irregularity of the ocular surface

21

Brown opacities of the corneum?

Epithelial
— pigmentary keratitis (melanin)

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

22

Black opacity in corneum of feline?

Feline corneal sequestrum
— necrotic corneal stroma


Occurs after chronic corneal ulceration often due to FHV1

23

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

Keratoconjunctivitis precipitates — cellular and fibrinous adhesions to endothelial surface

Usually settles in the ventral corneal

24

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

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