Corneal ulcers Flashcards
what is a corneal ulcer
break in continuity of corneal epithelium with exposure of underlying stroma
List 5 ways that the cornea maintains transparency
Smooth optical surface
Relatively dehydrated state
Very regular arrangement of collagen fibrils
Low cell density
No keratin, blood vessels or melanin
List 3 cornea pathologies
oedema
vascularisation
pigmentation
Describe corneal wound healing
corneal epithelium is self-renewing: continual cell turnover
Describe how the cornea heals a superficial ulcer
Epithelial loss -> cells slide rapidly across to cover defect (hours – days): cell proliferation, migration and adhesion
Takes a few days
Describe stromal wound healing
Starts once re-epithelialisation is complete
Fibroblasts migrate in & lay down new collagen
Requires vascularisation
Results in scar tissue: remodelling over time
List 6 causes of corneal ulcers in dogs
trauma
tear film problem
adnexal conditions
primary corneal disease
infection
neuro disease- facial or trigeminal nerve paralysis
what do corneal ulcers secondary to dry eye (KCS) look like
have a circular ‘punched out’ appearance and deteriorate rapidly
List the clinical signs of corneal ulceration
Ocular Pain
Conjunctival hyperaemia - a “red eye”
Ocular discharge
Corneal oedema
Reflex uveitis
describe the TRIAD of ocular pain
- Increased lacrimation (high STT)
- Blepharospasm - closing eye
- Photophobia - avoiding bright light
Describe a superficial corneal ulcer
epithelial loss on
acute onset
painful
sharp distinct border
Describe a stromal ulcer
Loss of epithelium and stroma
Acute or chronic
Fluorescein stains walls and floor of ulcer
anterior uveitis common
Describe how to tell the difference between a superficial and stromal ulcer
stromal- will see crater in cornea when look at eye from different angle
Describe a Descemetocoele
Complete stromal loss - defect down to Descemet’s membrane
Walls of ulcer/crater usually obvious
Don’t take up stain in the middle- look black - shows descements membrane does not take up stain
Describe a ‘melting’ corneal ulcer (keratomalacia)
Beware the animal with an acute closed painful eye with copious discharge – probably “melting”
acute- painful
Lots of gelatinous “gloopy” discharge
Ill-defined, rounded, soft edges
Describe what melting corneal ulcers look like
ill-defined rounded soft edges
marked corneal oedema
marked anterior uveitis
Can progress rapidly and perforate within hours: ophthalmic emergency
Describe the pathogenesis of melting ulcers
Enzymes (proteinases and collagenases) break down or ‘digest’ corneal stroma
2 origins:from cornea itself OR bacterial infection
topical corticosteroids cause local immune suppression and potentiate collagenase activity
List 5 questions that we should you ask ourselves when approaching treating a corneal ulcer
How big/deep is it?
Where in the cornea is it?
Does the surrounding cornea look healthy?
Is there an underlying cause?
Is it melting/infected?
Decsribe how to treat a superficial corneal ulcer
underlying cause
chloramphenicol drops QID
systemic NSAID
if any reflex uveitis- single drop of atropine
recheck 3-5 days
Describe how to treat superficial stromal corneal ulcers
underlying cause
chloramphenicol drops QID
systemic NSAID
if any reflex uveitis- single drop of atropine
recheck 3-5 days
what is a complex corneal ulcer
Deep stromal ulcer
Descemetocoele
Perforated ulcer
Melting ulcer
What diagnostics should we perform if think corneal ulcer is infected
corneal cytology
corneal swab
care with deep lesion- procedure can cause corneal perforation
Describe how to treat melting corneal ulcers
ideally base ABs off C and S
consider systemic ABs
anti-collagenase q2h
systemic NSAID +/- opiod
atropine to effect
may need surgery
monitor closely
Describe Anti-collagenases for melting ulcers
serum from same or other animals
OR
N-acetylcysteine - Stromease relatively new licensed product, synthetic alternative to serum
Describe how to treat deep ulcers
Intensive medical therapy following general principles
Prompt grafting surgery to prevent corneal perforation
If perforated or referral not possible - enucleation may be required
SCCED
spontaneous chronic corneal epithelial defect
Describe what a SCCED is
Aka non-healing ulcer, indolent ulcer, ‘Boxer ulcer’
Superficial ulcer that affects middle-aged dogs (>7 years old)
can affect any breed
epithelial loss only - NO stromal involvement
what occurs in a SCCED
Characterised by lip of loose epithelium – epithelium grows across but cannot adhere to underlying stroma
Describe diagnosis of SCCED
- Signalment: older dogs
- Clinical appearance: superficial, non-adherent epithelium
- Ruling out other underlying causes e.g. ectopic cilium, foreign body, eyelid mass, KCS…
Describe how to treat SCCEDs
Need to disrupt the epithelial basement membrane/anterior stroma to allow epithelium-to-stroma attachment – medical treatment alone not enough
Debridement alone OR debridement + keratotomy or Keratectomy
in conjunction with medical treatment
Describe the adjunctive medical therapy used to treat SCCEDs
debridement/keratotomy
chloramphenicol
systemic NSAIDs
1-2 drops of atropine
List 3 common causes of corneal ulcers in cats
Infection: feline herpesvirus infection (FHV-1)
Trauma (cat fight injuries, FB)
Corneal sequestrum
