Diseases Of The Cornea Flashcards by Vet Med

Purpose of cornea

Clear medium for vision
Gross focus
Protection
Refraction

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What are the layers of the cornea

Outer epithelium
Stroma
Descemet’s membrane
Innermost endothelium

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Where does the cornea get its blood supply

Aqueous humor

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Why is the cornea clear

Avascular
Anhydrous
Regular arrangement of collagen fibers

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What can make the cornea opaque

Cellular infiltrate 
Fibrosis
Pigment
Neovascularization
Edema
Mineralization

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What is the difference in location of abscess and white blood cell in cornea

White blood cell behind.

Abscess in the middle of it

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Infiltrate color

Creamy

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Fibrosis color

Grey
A scar
Response to healing

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Fibrosis characteristics

End result of healing

No fluid

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What causes Pigment problems

Secondary to chronic irritation
Caused by trichiasis
Chronic dry eye
Pannus

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What causes vascularization

Inflammatory stimulus

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Characteristics of vascularization

Can be deep or superficial
Leak into cornea
Usually see with edema

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Superficial vascularization

Single ‘Tree’

Dry eye

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Deep vascularization

Many ‘Bushes’
Glaucoma
Uvitis

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Edema

Fluid in corneal stroma

Occurs at different levels

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What color is edema

blue with indistinct border

Can have white blisters which can pop causing ulcer

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Mineralization

Dystrophic along with a degenerative disease
Underneath epithelium
Difficult to treat

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Color of mineralization

Chalky white

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Corneal ulcers

Most common ophthalmic condition seen in practice

Loss of corneal tissue

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What takes up stain

Stroma if it’s exposed

Not endothelial cells

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Are blood vessels good with ulcers

Yes

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What do you base your treatment plan on with ulcers

Depth

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Superficial ulcers

Epithelium is the only structure missing

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What has to happen for superficial ulcer to heal

Epithelial cells around ulcer will migrate in and cover the wound
Stem cells supply epithelial cells

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How fast does an epithelial injury heal

.6-1mm/day

How long does it take for a superficial ulcer to completely heal

6 weeks

Stromal ulcer

Varying degrees of stromal collagen lost in addition to epithelium

What happens if you see white blood cell around the stromal ulcer

Infection

stroma response to injury

Re-synthesis and cross linking of collagen PMN appear around edge Transform into fibroblasts and produce collagen

Cillary flush

Vessels engorge | Endothelial budding of blood vessels

How long does cillary flush take

5ish days | Endothelial cells of blood vessels bud off into the stroma

What happens to the blood vessels after they are done doing their job

Ghost vessel | Vessel walls are there, but no blood

How fast do WBC move in the cornea

9mm/day

Haw fast do corneal blood vessels and epithelial cells move

1mm/day

Importance of ghost vessels with reoccurring ulcer

The vessels will re profuse faster than if new ones had to be grown

Dermoid

Normal tissue in an abnormal location

Diagnosis of corneal ulcer

Treat aggressively Recheck often Assume it will get worse

Clinical signs of corneal ulcer

``` Blepharospasm (squinting) Epiphora (tearing) discharge Secondary anterior uvitis Miosis Corneal edema Corneal vascularization ```

Corneal ulcer diagnostics

Fluorescein every painful eye Schirmer tear test (if recurrent) Culture

What should your STT be in an ulcerated eye

Increased tearing

Corneal cytology

Topical anesthesia Back of scalpel blade Diff-quick and gram stain

Descemetoceles

Epithelium and stroma lost Very thin Only DM remains

Iris prolapse

DM ruptures | Iris passively flows AqH and plugs hole

Melting ulcers

Proteases destroy Look soft Infection

How do distinguish melting ulcers from corneal edema

Melting ulcers are soft

Do you use corticosteroids topically on a corneal ulcer

NEVER

How do you tell if ulcer is infected

``` Cellular infiltrate Melting Degree of uveitis Delayed healing Positive culture ```

What species is herpies most common

Cats

How does the corneal ulcer appear with herpies

Branching ulcer

Therapy of corneal ulcer

Support wound healing | Body will heal itself

What determines the treatment for ulcer

``` Primary etiology Infected Depth Melting Extent of uveitis ```

Goals of therapy

Sterilize the wound Control 2nd anterior uveitis Slow collagen breakdown Provide structural support

Medical treatment of ulcers

Treat etiology Broad spectrum topical antibiotics Reduce tear protease activity Treat Uveitis

Hypopians are most often...

Sterile

Treatment of reflex uveitis

Atropine | Systemic NSAID

Superficial ulcer treatment

antibiotic Atropine E collar

Stromal/complicated ulcer

``` Antibiotics Antifungals if needed Serum, EDTA, Atropine Systemic NSAID Maybe surgery ```

Melting ulcer treatment

Very aggressive medical/surgical treatment | Do everything.....except topical steroids

Anti-melting therapy

Serum/plasma EDTA N-acetylcysteine

Deep ulcers, descemetoceles, and perforated ulcer treatment

Aggressive medical therapy antibiotics Surgery

Iris prolapse treatment

Emergency Systemic antibiotics No oitments

Corneal foreign body ulcer. Treatment

Remove and treat as ulcer

Non-healing ulcer causes

Look at eyelid/lashes Tear production Foreign bodies

Refractory ulcers

Superficial corneal erosion with epithelial 'lips' | Epithelial roll back, mitosis, but cannot adhere

indolent ulcer

Defect in hemidesmosomes of basal corneal epithelial cells

Treatment for indolent ulcer

Remove with a q-tip

Why can't grid horses

Horses: usually have fungal issues that can get dragged deeper

Keratitis

Non-specific inflammation of the cornea

Pannus

AKA chronic superficial keratitis Immune mediated German shepherds

Pannus treatment

Topical steroids No cure Topical cyclosporine

Pannus looks like

Pigment and vessels coming from lateral

Immune mediated process where the body is reacting to a virus. Chronic.

Hermetic stromal keratitis

Hermetic stromal keratitis managment

Steroids, CsA, antiviral

Proliferative keratitis Non-healing ulcer Caused by tumor

Eosinophilic keratitis

How to diagnose eosinophilic keratitis

Cytology

Inherited, breed related disease. Affects both eyes No corneal inflammation

Corneal dystrophies in dog

Endothelium response to injury

Limited capacity for regeneration

What happens when endothelium is damaged

Fluid isn't pumped out

*Hallmark of corneal endothelial disease*

Corneal edema

Treatment of endothelial disease

Topical hyperosmotics Thin permanent grafts Thermal keratotomy

Diseases Of The Cornea Flashcards

(80 cards)