Diseases Of The Cornea Flashcards
Purpose of cornea
Clear medium for vision
Gross focus
Protection
Refraction
What are the layers of the cornea
Outer epithelium
Stroma
Descemet’s membrane
Innermost endothelium
Where does the cornea get its blood supply
Aqueous humor
Why is the cornea clear
Avascular
Anhydrous
Regular arrangement of collagen fibers
What can make the cornea opaque
Cellular infiltrate Fibrosis Pigment Neovascularization Edema Mineralization
What is the difference in location of abscess and white blood cell in cornea
White blood cell behind.
Abscess in the middle of it
Infiltrate color
Creamy
Fibrosis color
Grey
A scar
Response to healing
Fibrosis characteristics
End result of healing
No fluid
What causes Pigment problems
Secondary to chronic irritation
Caused by trichiasis
Chronic dry eye
Pannus
What causes vascularization
Inflammatory stimulus
Characteristics of vascularization
Can be deep or superficial
Leak into cornea
Usually see with edema
Superficial vascularization
Single ‘Tree’
Dry eye
Deep vascularization
Many ‘Bushes’
Glaucoma
Uvitis
Edema
Fluid in corneal stroma
Occurs at different levels
What color is edema
blue with indistinct border
Can have white blisters which can pop causing ulcer
Mineralization
Dystrophic along with a degenerative disease
Underneath epithelium
Difficult to treat
Color of mineralization
Chalky white
Corneal ulcers
Most common ophthalmic condition seen in practice
Loss of corneal tissue
What takes up stain
Stroma if it’s exposed
Not endothelial cells
Are blood vessels good with ulcers
Yes
What do you base your treatment plan on with ulcers
Depth
Superficial ulcers
Epithelium is the only structure missing
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
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
