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Flashcards in cornea Deck (78):
1

corneal histology

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A-epithelium

B-stroma

C-Descemet's membrane

D-endothelium

thickness: 500 to 800 um

2

corneal epithelium

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25 to 40 um in domestic carnivores

2-4x thicker in ungulates

nonkeratinized stratified squamous (G)

single layer of basal cells (A)

richly innervated (H)

hemidesmosomes

hydrophobic

3

corneal stroma

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90% of corneal thickness

 collagen

nerves are located in anterior portion

hydrophilic

4

descemet's membrane

basement membrane for endothelium

acellular

PAS +

hydrophobic

5

Endothelium

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single cell layer

hexagonal cells-minimal to no regeneration

Na+/K+ ATPase pump-keep fluid out of cornea

 

6

normal cornea

clear, colorless

smooth, hydrated

nutrition-precorneal tear film, aqueous humor

functions: light refraction, transmission of light

7

What allows the cornea to function properly

lack of pigment

lack of blood vessels

nonkeratinized epithelium

relatively low cell density

surface irregularities smoothed by mucin

relative dehydration

specific arrangement of stromal collagen

8

corneal deturgescence

hypertonicity of precorneal tears

hydrophobic epithelium

endothelium-most important factor with a Na+/K+ ATPase pump and tight intercellular junctions

9

collagen arrangement

parallel lamellae

close, regular spacing of lamellae

minimal light scattering

if not parallel will cause a glare

10

response to disease

epithelial metaplasia-keratinization, pigmentation (melanin), squamous metaplasia

inflammation-vascularization, edema

corneal ulceration

deposits into the cornea

necrosis

11

Corneal edema

often cobblestoned appearance

edema in the interlammellar spaces

focal implies epithelial disruption-superficial corneal ulcer

diffuse implies endothelial compromise-uveitis, glaucoma, deep corneal ulcer

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12

corneal fibrosis

wispy grey

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13

White blood cells in cornea

yellow/cream

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14

cornea lipid and mineral deposits

sparkly

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15

corneal melanosis

due to chronic irritation

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16

corneal vascularization

indicates chronicity

superficial vessels and deep vessels

17

vascularization: superficial vessels

ocular surface disease

long thin branching "trees"

 

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18

vascularization: deep vessels

deep corneal disease or intraocular disease

short, wider, little branching, "hedges"

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19

diagnostic algorithm for patients with corneal vascularization

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20

corneal healing: Epithelial defects

includes defects of epithelium only or epithelium and anterior 25% of stroma

the epithelial cells flatten and sliding around the wound margin to heal the area

epithelial cells can undergo mitosis

21

Corneal healing: stroma

involves >25% of stroma

epithelial healing occurs

fibroplasia occurs (ie resting stromal keratocytes undergo activation to become fibroblasts)

collagen is synthesized and reorganized

angiogenesis occurs if lesion is deep, infected or chronic

slow and imperfect-->reduced corneal transparency

22

corneal healing: Full thickness defects

wound selead with fibrin plug and corneal edema

WBC migrate in via tears, aqueous and corneal vessels

epithelium slides over to cover defect

stromal healing occurs

endothelial cells slide and some mitosis occurs followed by Descemet's membrane formation

23

Examination and dx testing

transillumination

slit beam

STT

TFBUT

Flurescein stain

Cytology, C&S

 

24

Examination and Dx testing: transillumination

opacities will block light passage

alter the angle of light often to see differences in opacities

reflections on the cornea indicate hydration and presence of irregularities (may look mottled, crisp)

25

Examination and dx testing: slit beam

Purkinje image 1 is cornea

If lesion is in front part of image, it is an subepithelial lesion

if lesion is in back part of image, it is on the endothelium

can determine depth of lesion

26

Examination and Dx testing: STT

for quantative tear film evaluation

normal in dogs >15 mm/min

cats-variable

27

Examination and dx testing: TFBUT

for qualitative tear film disorders

normal ~20 sec in dogs, ~16 sec in cats

28

Examination and dx testing: Fluorescein stain

adheres to hydrophilic stroma-ID corneal ulcers

apply anywhere on ocular surface except cornea

do not dilute in >0.5 ml eye wash

use cobalt blue filter to improve visualizatino of uptake

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29

Examination and dx testing: Cytology, C&S

swab, spatula lesion

topical anesthetic required

ID microogranisms

chacterization of corneal infiltrates

30

Dermoid

normal tissue in abnormal area

common locations: lateral limbus, third eyelid, eyellid

refer to ophthamologist

 

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31

Corneal dystrophy

inherited subepithelial deposits

purebred dogs

usually appear by 2 years of age

lipid

bilateral

cystalline, oval opacities in central cornea

finite size

rarely results in visual compromise

r/o systemic hyperlipidemia

no tx

 

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32

diagnostic algorithm for corneal lipid and mineral deposits

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33

dx algorithm for corneal ulceration

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34

sequalea of corneal ulceration

infection

globe rupture

pain

reflex uveitis

35

clinical signs of corneal ulceration

blepharospasm

epiphora

rubbing at eyes

conjunctival hyperemia

episcleral congestion

cheomsis

ocular discharge

older ulcers: corneal edema and vascularization

corneal cellular infiltrate

uneven corneal surface, divoting

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36

principles of corneal ulceration therapy

remove underlying cause

topical abx

pain management

anti-inflammatory therapy

prevention of self trauma

secondary complications

37

topical abx therapy

prevent/tx infection

normal flora source of opportunistic infection

broad spectrum

38

pain management of corneal ulcers

topical atropine-paralyzes ciliary body to prevent muscle spasm, use loweset effective dose

topical preservative free 1% morphine

39

anti-inflammatory therapy for corneal ulcers

use if significant anterior uveitis is present

oral administration preferred

topical steroids CI

topical NSAIDs may potentiate collagenolysis

40

prevetation of self trauma for corneal ulcers

E-collar

doggles

optivizor

41

secondary complications

elevated risk of rupture with stromal loss

collagenolysis

infection

42

follow up for corneal ulcers

recheck 5-7 days

repeat ophthalmic examination with fluorescein stain

negative-disconintue meds and E-collar removed

positve: continue tx, recheck within 7 days

43

simple corneal ulcer

acute

loss of epithelium only

not infected

should heal within 7 days

tx: topical abx, +/- pain management

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complicated corneal ulcer

does not heal within 7 days +/or stromal loss

persistent underlying cause

45

indolent corneal ulcer

aka spontaneous chronic corneal epithelial defect, boxer ulcer

abnormal attachments between epithelium and anterior stroma

Not infected

predisposed: older dogs, boxers, corgis

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46

dx of indolent corneal ulcer

chronic hx

signalment

loose epithelial edges, superficial, no evidence of infection

47

medical tx for indolent corneal ulcers

topical abx

pain control

corneal lubrication

corneal debridement and grid keratotomy

contact lens placement

e-collar/doggles/optivizor

48

corneal debridement and grid keratotomy

removal of hyaline acellular zone

exposes stroma

promotes formation of attachments with epithelium

85% chance success

49

follow up for indolent corneal ulcer

recheck 2 weeks

remove contact lens

fluorescein stain-negative stop tx, positive-repeat debridement and grid keratotomy (up to 2-3 times)

refer if not healing

50

complicated corneal ulcer

chronic or have stromal loss, with concurrent underlying ophthalmic disease

includes: indolent, deep, melting and lacerations/perforations

51

deep corneal ulcer

stromal loss

depth assessed by slit beam

significant uveitis

assume infection

risk of globe perforation

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dx for deep corneal ulcer

ophthalmis exam

cytology

C&S

53

Descemetocele

only Descemet's mebrane and endothelium intact

risk of perforation immediate

descemet's membrane will not retain fluorescein stain

54

medical tx for deep corneal ulcers

solutions only!

abx-do C&S but start abx prior to results, okay to use big guns such as fluoroquinolones

anti-inflammatory & analgesic-topical atropine, topical morphine, oral NSAIDs

E-collar, doogles, optivizor

refer for surgical graft

55

melting corneal ulcers

collagenolysis occurring

cornea becomes white/yellow and friable or liquid

can progress rapidly

significant uveitis

assume infection

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56

melting corneal ulcers dx

ophthalmic exam

cytology

C&S

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melting corneal ulcer tx

aggressive therapy

solutions only

abx q 1-2 h for 1-2 days, then q6h

pain control: topical atropine and morphine, oral NSAIDS

decrease uveitis-no topical steroids!

protease inhibitors-N-acetylcysteine, EDTA, doxycycline, serum!

E-collar, doogles, optivzor

refer for surgical graft

58

corneal lacerations and perforations

full thickness corneal injury

trauma

progression of deep and melting corneal ulcers

px guarded when there is lens involvement, hyphema, laceration size, limbal involvement, posterior segment involvement

urgent referral

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corneal lacerations and perforations tx

aggressive medical tx

laceration repair

+/- FB removal

+/- surgical graft

+/- cataract sx

enucleation

60

Feline corneal ulcers

FHV-1

dendritic corneal ulcers

stromal keratitis

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61

principles of ulcer therapy in cats

remove underlying cause

abx therapy-must be able to kill C. felis and Mycoplasma

pain management

anti-inflammatory therapy

prevention of self-trauma

address secondary complications

antiviral therapy

FHV-1 Therapy: mucinomimetic lacrimomimetics, antivirals, L-lysine, decrease stress

62

eosinophilic keratoconjunctivitis

unknown cause-maybe immune-mediated

concurrent corneal ulceration common 

 

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63

eosinophilic keratoconjunctivitis: clinical signs

conjunctivitis, raised, white to tan corneal plaques, superficial corneal vascularization, corneal edema

purkinje image 1 slightly elevated

 

64

eosinophilic keratoconjunctivitis: dx

dx: appearance, cytology-eos, mast cells, PMN, hyperplastic or dysplastic epithelial cells

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eosinophilic keratoconjunctivitis: tx

antivirals

abx

tear film supplementation

anti-inflammatory/immunosuppressive meds-okay to use if ulcer present

66

eosinophilic keratoconjunctivitis:px

recurrence is common

some cats req long term therapy

67

corneal sequestrum

corneal necrosis

discoloration ranges from light brown to black

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68

corneal sequestrum tx

address/remove source of irritation

treat corneal ulcer

treat uveitis and pain

refer for keratectomy and corneoconjunctival transposition

recurrence in 33%

69

pannus

aka chronic superficial keratitis

immune-mediated inflammation of the cornea with melanosis and/or fibrovascular proliferation

predisposed: GSD, greyhound

exposure to UV light worsens disease

usually bilateral

70

pannus presentation

bilateral, progressive infiltration of the corneas

can be blinding

third eyelid sometimes involved

most lesions start laterally

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71

pannus therapy

require for life to minimize progression

immune suppression/anti-inflammatory: Prednisolone or dexamethasone, Cyclosporine A

limit exposure to UV light

72

pigmentary keratitis

bilateral, progressive melanosis and keratitis

brachycephalic ocular syndrome

73

how to differentiate pigmentary keratitis from pannus

breed

facial conformation

pigment distribution-medially

74

pigmentary keratitis: tx

eyelid sx

address underlying cause-lubrication, anti-inflammatories, medial canthoplasty

75

corneal deposits

usally subepithelial

may or may not be associated with ocular irritation, ocular disease or systemic disease

76

causes of lipid/mineral deposits in dogs

genetics (corneal dystrophy)

ocular inflammation-keratitis, uveitis

steroid keratopathy

hyperlipidemia

endocrinopathy

77

dx testing with corneal deposits

if bilateral, symmetrical in young purebred dog-corneal dystrophy-no tx

r/o endocrinopaties

checks serum cholesterol, triglycerides

78

tx for corneal deposits

often no therapy

diet change

chelation therapy if mineral

keratectomy