Corneal Ulcers Flashcards
Label the corneal anatomy
A) Epithelium
B) Stroma
C) Descemet’s membrane= basement membrane
D) Endothelium
How much of the cornea is stroma?
90%
Why are there nerve endings in epithelium and stroma of the cornea?
–Superficial lesions can be more painful than deeper lesions
–Cornea is very sensitive
–This is for protection to allow the eye to blink when something painful touches
What maintains the cornea in a dehydrated state?
Endothelial ‘pump’
How does oedema occur in the cornea?
–Increased water content distorts collagen fibrils which creates opacity (cloudy eye)
–Occurs when barrier layers (epithelium and endothelium) breached/dysfunctional
Why is the cornea well vascularised?
To promote healing
How does the cornea epithelium heal?
–Cells SLIDE rapidly across defect (hours to days) to cover defect
–Mitosis
–Outer multi cell layer. “walk across corena” with feet
How long does it take for the cornea to re-epithelialise?
7 days
How does the corea stroma heal?
–Stromal healing only starts once defect is ‘covered’ by epithelial layer
–Regeneration from fibroblasts (weeks)
How does the descemets membrane heal?
–Elastic, limited ability to repair
What is the cornea’s epithelium healing like?
Very poor ability to repair
Name 7 causes of ulcers (9)
- Adnexal condition
- Eyelids
–Entropion (inversion of eyelid margin)
–Ectropion (eversion of eyelid margin)
–Eyelid margin mass
–Trauma e.g. cat fight
•Eyelashes
–Distichiasis (extra eyelashes)
–Ectopic cilia (extra eyelash from palpebral conjunctiva)
•Conformation
–Trichiasis (normal skin hairs contacting eye, e.g. nasal fold trichiasis)
–Lagophthalmos in brachycephalic breeds (see later)
•Trauma
–Common
–FB, abrasion, laceration
–Chemical burns (serious but uncommon)
•Tear film problem
–Dry eye (quantitative - very common in dogs)
–Qualitative tear film problem (less common)
•Primary corneal disease
–Spontaneous chronic corneal epithelial defect (SCEDD)
–Epithelial defect – will be open to infection. The infection eeps the baddies out so when you loose this the lesion is susceptible to colonisation!
•Infection
–Usually secondary to trauma to allow bacterial colonisation
–Bacterial keratitis
–Fungal keratitis (uncommon)
•Neurological disease
–Neuroparalytic keratitis (facial nerve paralysis, unable to blink)
–Neurotrophic keratitis (reduced or absent corneal sensation, trigeminal nerve problem); uncommon.
What is this?
Distichiasis
(extra eyelashes)
How might an eye wart cause an ulcer?
Pedcunculated
What is seen?
Dry eye KCS
Ulcers secondary to dry eye often have a circular ‘punched out’ appearance and deteriorate rapidly
Name 2 reasons brachycephalic dogs are at risk of ulcers (3)
•Shallow orbit results in prominent globe
–Reduced blinking (lagophthalmos)
–Poor distribution of tear film
- Medial lower entropion
- Nasal fold trichiasis
What is normal in brachycephalic cats which can go on to cause an ulcer? E.g. Persian cats
Medial lower
entropion.
What is this?
Hint: Pekingese dog
Nasal fold trichiasis and stromal ulcer
All the hairs are rubbing on the medial cornea = ulcer
Name clinical signs of corneal ulcers
•Pain - classic TRIAD of ocular pain
1) Increased lacrimation (high STT)
2) Blepharospasm - closing eye
3) Photophobia - avoiding bright light
- Conjunctival hyperaemia - a ‘red eye’
- Ocular discharge
- Corneal oedema
- Reflex uveitis – tends to be 2dry
How can we diagnose corneal ulcers?
- Direct observation
- Palpebral and corneal reflex
- STT – ensure no dry eye
–Eye might be too painful!
–Sometimes there is so much liquid this is pointless
- Fluorescein dye
- Corneal cytology (histopathology)
- Corneal culture & sensitivity
How can we highlight fluorescin dye further?
Blue light e.g. wood lamp
Name a structure fluorescin dye does NOT stain (2)
–Intact corneal epithelium (hydrophobic)
–Descemet’s membrane
Using the arrows label the corresponding ulcers
A) Superficial ulcer
B) Stromal ulcer
C) ADescemetocele
What is an indolent ulcer?
–Specific type of superficial ulcer
What is a corneal facette?
–Healed stromal ulcer with intact epithelium
What is seen with a superficial corneal ulcer?
- Epithelial loss only
- Acute onset
- Painful (nerve endings are more dense in superficial corneal layers)
- Sharp distinct borders
- Minimal corneal inflammatory response
- +/- Reflex uveitis
What is this?
Superficial corneal ulcer
What is the stain of a simple superficial ulcer?
Fluorescein staining pattern – goes to the edge
How do we treat a superficial ulcer?
- Identify and treat underlying cause
- Prevent secondary infection
–Topical antibiotic
–e.g. fusidic acid q12h, chloramphenicol q8h
- Analgesia, e.g. systemic NSAIDs
- Atropine drops – single application usually enough
- +/- E-collar
- Re-check in 3-5 days
–Re-check 1-2 days if brachycephalic breed
- Tend to heal alone
- Always be more cautious with brachy dogs
SCEED:
A) What is it?
B) How does it present?
A) Spontaneous chronic corneal epithelial defect
B) Unilateral
SCEED:
A) What is lost?
B) How much of the stroma is involved?
C) What happens?
A) Epithelium
B) None
C)Epithelium grows across but does not adhere to underlying stroma
How does SCEED present with fluorescein dye?
Ulcer has indistinct, irregular border which under-runs
What is this?
SCEDD
How can we manage SCEDD?
•Debridement
–Removes loose epithelium
•Keratotomy/keratectomy
–Procedures involving corneal stroma
–Promote epithelial adhesion
What are the management options for SCEDD?
- Debridement alone
- Debridement + keratotomy
- Debridement + keratectomy
- All options are in conjunction with medical treatment
Discuss the how to and the use of debridment for SCEDD
- Apply topical anesthetic eye drops
- Sterile bacteriology swab
–Or Q-tip but non-sterile
- Gentle but firm action to remove all loose epithelium
- True extent ulcer becomes apparent
–Don’t worry – it is only possible to remove abnormal epithelium but ulcer can become much larger!
•Success rate: 50% heal with debridement and medical treatment
How would you do a keratotomy?
–Debride first
–Use 25 -27 gauge needle, bevel up
–Needle parallel to corneal surface, drag (don’t push)
–Create cross-hatch of superficial lines 1mm apart
–Clear cornea to clear cornea, i.e. treat entire debrided area and 1-2mm into surrounding normal cornea
Name treatment options for SCEDD
•Prevent secondary infection
–Fusidic acid, chloramphenicol
–Tetracycline (topical or systemic)
- Analgesia, e.g. systemic NSAIDs, tramadol
- Atropine drops, 1-2 doses usually enough
- +/- Contact lens
- E-collar
What is the alternative for cross hatch keratectomy?
Burr keratectomy
Surgical keratectomy:
A) Name a negative
B) Name a positive
A) Need a specialist
B) 100% success
What about this tells us there is a loss of stroma?
Crater appearance
What is descemetocoele?
- Complete stromal loss - defect down to Descemet’s membrane
- Walls of ulcer/crater usually obvious
What colour does Descemetocoele stain?
Walls stain positive (exposed stroma)
Descemet’s membrane does NOT stain with fluorescein
Floor/base of ulcer looks black or clear
What is this?
Descemetocoele
How mght you get a false negative with Descemetocoele?
Without flushing after the dye; might not have clear centre
What is the thickness of Descemet’s membrane in adult dog?
•10-15μm
How can we treat descemetocoele?
- Intensive medical therapy following general principles
- Prompt surgery to provide tectonic support to prevent corneal perforation
What are the signs of a deep stromal ulcer?
- ‘Melting’ ulcer or keratomalacia
- Acute, painful
- Copious gelatinous ‘gloopy’ discharge
- Marked corneal edema
- Marked anterior uveitis
What are these?
Keratomalacia - melting ulcer
What is the pathogenesis of a melting ulcer?
- Enzymes (proteinases and collagenases) break down or ‘digest’ corneal stroma
- Two origins
–Cornea itself: epithelial cells, stromal fibroblasts, WBCs
–Bacterial infection, e.g. Pseudomonas sp, β-hemolytic Streptococcus sp
- Topical steroids cause local immune suppression and potentiate collagenase activity
- Assume infected until proven otherwise
How do we diagnose complex ulcer?
•Corneal cytology
–Gently scrape margin of ulcer (not base)
•Corneal swab
–Bacterial culture and sensitivity
–Fungal culture (esp horses)
–Swab margin of ulcer (not base)
•Care with very deep lesions – procedure can cause corneal perforation!
How can we treat deep ulcers?
- Similar principles as for simple superficial ulcer but MUCH MORE INTENSIVE
- Prevent and/or treat secondary infection
–Select antibiotic based on cytology/culture
–Fluoroquinolone, e.g ciprofloxacin, q2-6h
–Systemic antibiotics - broad
- Analgesia, e.g. systemic NSAIDs, tramadol
- Treat uveitis more aggressively
–Topical atropine to effect, e.g. once daily
–Systemic NSAIDs
•Consider corneal support
–Contact lens, glue, graft
- E-collar
- Monitor closely +/- hospitalise
- Melting ulcers: specific topical treatment – see next slide
What is anti-collagenase therapy?
Used for a melting ulcer
- Stop melting process with topical anti-collagenase therapy
- Apply q1-2h for 24h then gradually reduce
- Serum/plasma
- Na+/K+ EDTA solution
- N-acetyl-L-cysteine
How is surgery of deep ulcers best performed?
With magnification and microinstrumentation
What are the 3 top causes of ulcers in cats
–infection: feline herpesvirus infection (FHV-1)
–trauma (cat fight injuries, FB)
–corneal sequestrum
How can we treat indolent ulcers in cats?
•Gentle debridement & contact lens fine
Name 2 things we mut AVOID in the treatment of indolent ulcers in cats
- Keratotomy
- Phenol
What are the 3 main causes of ulcers in horses
–Trauma
–Bacterial infection
–Fungal infections common (keratomycosis)
