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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
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
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
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
32
diagnostic algorithm for corneal lipid and mineral deposits
33
dx algorithm for corneal ulceration
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
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
44
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
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
52
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
56
melting corneal ulcers dx
ophthalmic exam cytology C&S
57
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
59
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
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
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
65
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
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
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

Ophthamology (3 decks)

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