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Ophthamology > cornea > Flashcards

cornea Flashcards

1
Q

corneal histology

A

A-epithelium

B-stroma

C-Descemet’s membrane

D-endothelium

thickness: 500 to 800 um

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2
Q

corneal epithelium

A

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

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3
Q

corneal stroma

A

90% of corneal thickness

collagen

nerves are located in anterior portion

hydrophilic

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4
Q

descemet’s membrane

A

basement membrane for endothelium

acellular

PAS +

hydrophobic

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5
Q

Endothelium

A

single cell layer

hexagonal cells-minimal to no regeneration

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

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6
Q

normal cornea

A

clear, colorless

smooth, hydrated

nutrition-precorneal tear film, aqueous humor

functions: light refraction, transmission of light

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7
Q

What allows the cornea to function properly

A

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

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8
Q

corneal deturgescence

A

hypertonicity of precorneal tears

hydrophobic epithelium

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

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9
Q

collagen arrangement

A

parallel lamellae

close, regular spacing of lamellae

minimal light scattering

if not parallel will cause a glare

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10
Q

response to disease

A

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

inflammation-vascularization, edema

corneal ulceration

deposits into the cornea

necrosis

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11
Q

Corneal edema

A

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
Q

corneal fibrosis

A

wispy grey

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13
Q

White blood cells in cornea

A

yellow/cream

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14
Q

cornea lipid and mineral deposits

A

sparkly

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15
Q

corneal melanosis

A

due to chronic irritation

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16
Q

corneal vascularization

A

indicates chronicity

superficial vessels and deep vessels

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17
Q

vascularization: superficial vessels

A

ocular surface disease

long thin branching “trees”

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18
Q

vascularization: deep vessels

A

deep corneal disease or intraocular disease

short, wider, little branching, “hedges”

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19
Q

diagnostic algorithm for patients with corneal vascularization

A
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20
Q

corneal healing: Epithelial defects

A

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

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21
Q

Corneal healing: stroma

A

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

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22
Q

corneal healing: Full thickness defects

A

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

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23
Q

Examination and dx testing

A

transillumination

slit beam

STT

TFBUT

Flurescein stain

Cytology, C&S

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24
Q

Examination and Dx testing: transillumination

A

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)

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25
Q

Examination and dx testing: slit beam

A

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

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26
Q

Examination and Dx testing: STT

A

for quantative tear film evaluation

normal in dogs >15 mm/min

cats-variable

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27
Q

Examination and dx testing: TFBUT

A

for qualitative tear film disorders

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

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28
Q

Examination and dx testing: Fluorescein stain

A

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
Q

Examination and dx testing: Cytology, C&S

A

swab, spatula lesion

topical anesthetic required

ID microogranisms

chacterization of corneal infiltrates

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30
Q

Dermoid

A

normal tissue in abnormal area

common locations: lateral limbus, third eyelid, eyellid

refer to ophthamologist

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31
Q

Corneal dystrophy

A

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
Q

diagnostic algorithm for corneal lipid and mineral deposits

A
33
Q

dx algorithm for corneal ulceration

A
34
Q

sequalea of corneal ulceration

A

infection

globe rupture

pain

reflex uveitis

35
Q

clinical signs of corneal ulceration

A

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

36
Q

principles of corneal ulceration therapy

A

remove underlying cause

topical abx

pain management

anti-inflammatory therapy

prevention of self trauma

secondary complications

37
Q

topical abx therapy

A

prevent/tx infection

normal flora source of opportunistic infection

broad spectrum

38
Q

pain management of corneal ulcers

A

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

topical preservative free 1% morphine

39
Q

anti-inflammatory therapy for corneal ulcers

A

use if significant anterior uveitis is present

oral administration preferred

topical steroids CI

topical NSAIDs may potentiate collagenolysis

40
Q

prevetation of self trauma for corneal ulcers

A

E-collar

doggles

optivizor

41
Q

secondary complications

A

elevated risk of rupture with stromal loss

collagenolysis

infection

42
Q

follow up for corneal ulcers

A

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
Q

simple corneal ulcer

A

acute

loss of epithelium only

not infected

should heal within 7 days

tx: topical abx, +/- pain management

44
Q

complicated corneal ulcer

A

does not heal within 7 days +/or stromal loss

persistent underlying cause

45
Q

indolent corneal ulcer

A

aka spontaneous chronic corneal epithelial defect, boxer ulcer

abnormal attachments between epithelium and anterior stroma

Not infected

predisposed: older dogs, boxers, corgis

46
Q

dx of indolent corneal ulcer

A

chronic hx

signalment

loose epithelial edges, superficial, no evidence of infection

47
Q

medical tx for indolent corneal ulcers

A

topical abx

pain control

corneal lubrication

corneal debridement and grid keratotomy

contact lens placement

e-collar/doggles/optivizor

48
Q

corneal debridement and grid keratotomy

A

removal of hyaline acellular zone

exposes stroma

promotes formation of attachments with epithelium

85% chance success

49
Q

follow up for indolent corneal ulcer

A

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
Q

complicated corneal ulcer

A

chronic or have stromal loss, with concurrent underlying ophthalmic disease

includes: indolent, deep, melting and lacerations/perforations

51
Q

deep corneal ulcer

A

stromal loss

depth assessed by slit beam

significant uveitis

assume infection

risk of globe perforation

52
Q

dx for deep corneal ulcer

A

ophthalmis exam

cytology

C&S

53
Q

Descemetocele

A

only Descemet’s mebrane and endothelium intact

risk of perforation immediate

descemet’s membrane will not retain fluorescein stain

54
Q

medical tx for deep corneal ulcers

A

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
Q

melting corneal ulcers

A

collagenolysis occurring

cornea becomes white/yellow and friable or liquid

can progress rapidly

significant uveitis

assume infection

56
Q

melting corneal ulcers dx

A

ophthalmic exam

cytology

C&S

57
Q

melting corneal ulcer tx

A

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
Q

corneal lacerations and perforations

A

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

59
Q

corneal lacerations and perforations tx

A

aggressive medical tx

laceration repair

+/- FB removal

+/- surgical graft

+/- cataract sx

enucleation

60
Q

Feline corneal ulcers

A

FHV-1

dendritic corneal ulcers

stromal keratitis

61
Q

principles of ulcer therapy in cats

A

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
Q

eosinophilic keratoconjunctivitis

A

unknown cause-maybe immune-mediated

concurrent corneal ulceration common

63
Q

eosinophilic keratoconjunctivitis: clinical signs

A

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

purkinje image 1 slightly elevated

64
Q

eosinophilic keratoconjunctivitis: dx

A

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

65
Q

eosinophilic keratoconjunctivitis: tx

A

antivirals

abx

tear film supplementation

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

66
Q

eosinophilic keratoconjunctivitis:px

A

recurrence is common

some cats req long term therapy

67
Q

corneal sequestrum

A

corneal necrosis

discoloration ranges from light brown to black

68
Q

corneal sequestrum tx

A

address/remove source of irritation

treat corneal ulcer

treat uveitis and pain

refer for keratectomy and corneoconjunctival transposition

recurrence in 33%

69
Q

pannus

A

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
Q

pannus presentation

A

bilateral, progressive infiltration of the corneas

can be blinding

third eyelid sometimes involved

most lesions start laterally

71
Q

pannus therapy

A

require for life to minimize progression

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

limit exposure to UV light

72
Q

pigmentary keratitis

A

bilateral, progressive melanosis and keratitis

brachycephalic ocular syndrome

73
Q

how to differentiate pigmentary keratitis from pannus

A

breed

facial conformation

pigment distribution-medially

74
Q

pigmentary keratitis: tx

A

eyelid sx

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

75
Q

corneal deposits

A

usally subepithelial

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

76
Q

causes of lipid/mineral deposits in dogs

A

genetics (corneal dystrophy)

ocular inflammation-keratitis, uveitis

steroid keratopathy

hyperlipidemia

endocrinopathy

77
Q

dx testing with corneal deposits

A

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

r/o endocrinopaties

checks serum cholesterol, triglycerides

78
Q

tx for corneal deposits

A

often no therapy

diet change

chelation therapy if mineral

keratectomy

Ophthamology (3 decks)

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