04 - Cornea 1 (corneal ulceratio

Be familiar with the normal anatomy of the cornea and its appearance on histology • Be able to define corneal ulceration and have a basic understanding of normal corneal healing • Know the common clinical signs and causes of corneal ulcers • Understand how to distinguish uncomplicated superficial ulcers from deeper stromal ulcers and descemetocoeles • Know how to recognise SCCEDs, and be familiar with the use of diamond burrs and soft corneal bandage lenses in the treatment of this condition • Understand how ulcers may progress and deepen, and how to perform corneal cytology • Be familiar with the use of antimicrobials and anticollagenases in the medical management of stromal ulcers • Be able to recognise keratomalacia (melting) • Know when to recommend referral for treatment of ulcerative keratitis, and how to recognise corneal perforation

corneal anat

name the 4 lters

1) Epithelium
2) Stroma
3) Descemets membrane
4) Endothelium

corneo-scleral coat

outermost fibrous coat of the eye

junction between the cornea and sclera

limbus

avascular cornea nutrient supply

• aqueous,

• perilimbal capillaries

• tear film

cornea redlex

reflection of light in the cornea

• sharp and clear indicating an uninterrupted surface

• clear, smooth tear film

epithelium

• Non-keratinised, stratified squamous epithelium

• Rapid turnover of cells

• Forms a natural barrier to ingress of water from the
  tear film.

• Protects from colonization with bacteria/fungi

• Dependent on a normal and properly distributed tear
  film to function well.

• Basal cells attach to a thin basement membrane via
  hemidesmosomes, anchoring the epithelium to the
  underlying stroma

Stroma

• 90% of corneal thickness

• composed of collagen lamellae, separated by ground substance and modified fibroblasts (keratocyte).

• regular arrangement of lamellae is critical for transparency—> cornea must be kept dehydrated

• superficial stroma richly innervated by opthalmic division of CN V (trigeminal)

descemients membrane

• basement membrane of the endothelium,

• produced throughout life,

• elastic and fairly strong,

• does not stain with fluorescein

endothelium

• Maintains corneal dehydration through active transport of sodium into the aqueous humour (Na+/K+ ATPases).

• Poor regenerative capacity

• Decreased cell numbers with age

corneal epithelium importance

• provide protective barrier

  • resistant to bacterial colonisation

  • prevents water entering the cornea

corneal ulcer

Loss of full thickness of the epithelium (most often as a result of mechanical trauma) exposes the underlying stroma (± loss of stroma)

can progress to full thickness and perforation

cornela ulcer stain

mechanism

use fluorescein stian

• only strins exposed stroma.

• Epithelium or detdcements don’t stain fluorescein

limbus is where corea meet sclera where all stem cells are.

ulcer: simple and complicated

siple: within 7 days. non-infected, no ongoing underlying cause

complicated: fail to heal within 7days ,(ongoing re-eplitheliadlsica)

basic understanding of normal corneal healing

how logng should superficial ulcer need to heal

• epithelial defect healing usually rapid

  • migration of adjacent epithelial cell coevering defect

  • then replicate to restore full thickness

• superficial should heal within few days

stromal defect healing— scute superficial

Avascular healing (acute superficial stromal loss):

• Neutrophil infiltration

• New collagen secretion from activated keratocytes at the wound margin

deep/ chronic/ infected stromal ulcer healing

vascular healing

• extensive early cellular infiltration

• subequent vascualr invasion—> fibrovacualr granultion tissue at ulcer site

corneal ulceration: clinical signs

• marked pain and discomfort (blepharospasm)

  • care with CNV damage-→ sensation may be affected

• discharfege, epiphora and photophobia

  • + lacrimation—> epiphora

  • mucoid/ mucopurulent discharge common in melting/ infected ulcers

• Conjunctival hyperaemia.

• Variable localised corneal oedema I

• irregularity of the surface.

• Neovascularisation and cellular infiltration of the cornea is common with chronicity

• Reflex anterior uveitis

Causes of corneal ulcers

• External trauma / FB

• Hair/eyelash trauma – entropion+trichiasis, distichiasis, ectopic cilia

• Infection (secondary) – feline herpesvirus, bacterial colonization n

• Tear film abnormalities (KCS)

• Exposure keratopathy

• SCCED

• epithelial bullae rupture (secondary to marked corneal oedema)

• cholesterol/ calcium deposit—> erosion (rare)

cause of cornela ulcer

trauma due to suture contact
• Nylon suture in the upper eyelid
• As the dog blinks, the suture abrades the cornea
• granulation tissue—> going on for a considerable time

cause of cornela ulcer

trauma due to hair contacting the corneal surface
• Trichiasis due to entropion is a common cause of ulceration

cause of corneal ulcer?

ectopic cillia—> contacting corneal surface

less commonly, but usually cause a corneal ulcer when they do

• Young dogs, usually upper lid

• Linear corneal ulcer in the cornea corresponding to the cilia

• gunk and mucus trapping fluorescence around area

cause of corneal ulcer?

Nasal fold trichiasis and distichiasis (lashes on meibomian galnd) are common

aren’t always associated with corneal ulceration

cause of corneal ulcer?

exposure keratopathy

• Central corneal damage

• due to inadequate protection of thencornea

• by the eyelids and/or third eyelid

• compounded by inadequacy of pr-renal tear film

causes of exposure keratopathy

1. Prominent globe with poor lid closure

   • brachycephalic breeds often lagophthalmos – an inability to close the eyelids

   • chronic glaucoma: buphthalmus (globe enlargement)

   • retrobulbar masses—> exophthalmos

2. Facial nerve CN7 paralysis

   • more prominent more severely affected

   • loss of motor function to eyeylid—> cannot bink

3. Trigeminal nerve cN5 paralysis (check PPR, direct + indirect)

   • absent corneal sensation —> severe keratitis

   • Common complication of globe proptosis as nerve gets stretched.

   • brachycephalic breeds have reduced corneal sensation.

entropion, trichiasis, distichiasis

how does ruptured epithelial bulla cause corneal ulceration and what do you expect upon investigation

• large area of corneal oedema

• restricted area of fluorescein uptake—> small ulcer, likely a ruptured sub-epithelial bulla

• Fluorescein staining is less intense when there is corneal oedema

what is this cause of corneal ulcer

corneal cholesterol/calcium deposit:

rare, refer

Superficial ulcer- only the epithelium is los

stromal ulcer/ deep ulce

• ulcer is deeper than just the epithelium

• varying degrees of stromal loss

Descemetocoele

• ulcer extends through the entire stroma

• reach Descemets membrane

• descement membrane does not take up fluoroscien—> ring shape uptake

• cornea is in imminent danger of rupture

how deos ulcer progress

• Progressive loss of stroma: enzymatic degradation (collagenases and proteases)

• Some naturally produced by neutrophils; others are from infection (bacteria; especially Pseudomonas and Streptococcus)

• potentiated by corticosteroids

ulcer vs steroid

contraindication

____ with _____ or ________ results in a ______-tinged appearance

Infiltration with bacteria or neutrophils results in a yellow-tinged
appearance

how do you know bacteria present

Corneal cytology

• topical analgesia

• roll ‘Cytobrush’ or bacteriology swab along ulcer

• along the edge, avoiding the deeper centre;

  • care in very deep ulcers/ Descemetocoeles

• Roll swab onto a glass slide and ‘Diff Quick’

what do you do folowing corneal cytology

what Abx will you give if cone/ rods?

Directs immediate antibiotic use whilst awaiting culture and
sensitivity results

• cocci: chloramphenicol drop

• rods: : fluoroquinolone (ofloxacin aka exocin)

name most comon secondary bacterilainfection. name 2 gram +ve and 2 gram -ve

Gram positive cocci:

• Staphylococci

• Streptococci

Gram negative rods

• Pseudomonas

• E.coli

how would you describe thiss

melting ulcer, keratomalacia

melting ulcer aka keratomalacia

edge of ulcer: ____

deteriorate _____

• edges of the ulcer appear gelatinous

• can start when ulcer still shallow—→ acutely deteriorate

simple cornela ulcer tx: 6

most acute superficial ulcer heals quickly once cause is removed

however infection consequences are serious—> topical Abx until fluorascene negative.

1. Chloramphenicol drops 4x daily (or ointment 2x daily)

2. Analgesia

   • Systemic NSAID unless contraindicated

   • +/- paracetamol, tramadol, gabapentin if required

   • proxymetacaine contraindicated—> delay corneal healing, decrease protective mechanism like tearinng and blinking

3. Topical lubricant

   • increase rate reepithelialisation

4. +/- single drop of atropine (pupal dilation)
   – Improves ‘reflex uveitis’
   – reduce tear production—> contraindicate if KCS

5. Protective collar

6. Recheck in 2-5 days

simple corneal ulcer fails to heal within 7 days

re‐classified as a complicated’ corneal ulcer

underlying reason for failure of re‐epithelialisation identified and addressed

why could a simple ulcer not heal?

1. The underlyingcause has not been addressed

   • Ongoing trauma? (entropion, ectopic cilia, foreign body etc.)

   • KCS?

   • Exposure keratopathy?

2. Secondary infection with bacteria (or fungi)

   • corneal cytology

3. ulcer is SCCED

4. The patient is immunosuppressed/ immunocompromised

Superficial to mid-stromal ulcers can usually be managed ____.

what else would you do?

medically, but can progress quicky

• hospitalisation for close monitoring

• intensive topical treatment

• injectable analgesia (e.g. opioids)

typical regime for a stromal cornela ulcer ** exam

most common cause of stromal ulcer progression: secondary infection

—>corneal cytology and broad spec abx while C+C. chloramphenicol and ofloxacin can be used together if indicated.

1. Antibiotic drops:

   • base on cytology result, q 2-4 hours

   • fuscidic acid (Isathal) NOT an appropriate choice for stromal or malacic ulcers

2. **Anti-collagenase:

   • Autologous serum/plasma is the anti-collagenase of choice

   • Apply 10 minutes after the antibiotic, same frequency

3. Analgesia

   • Oral NSAID +/- paracetamol, gabapentin, tramadol etc.

   • +/- opioid if required

4. Topical atropine to effect (q24h until pupil is dilated); care in KCS

5. monitor q24-48h

malacia, deep ulcer (>50%) and descemetocoele

• refer as emergency

• may require corneal graft sx

what is SCCED

Spontaneous chronic corneal epithelial defect (‘indolent’ or ‘Boxer ulcer’)

• superficial ulcer

• failure of adhesion of epithelium to underlying stroma—> peel back readily

• rarely infected

• middle age to older animal

histopathology of SCCED

• failure of adhesion of the epithelium to the superficial stroma

• abnormal, thin, hyaline membrane on the exposed stromal surface, effacing the normal epithelial BM.

• flap or underrun edge at the ulcer margin

in 3 words describe scced tx

medical, surgical, ±contact lens

SCCED treatment : medical, surgical, others

same as simple crneal ulcercorneal medically

1. Chloramphenicol drops 4x daily (or ointment 2x daily)

2. Analgesia

   • Systemic NSAID unless contraindicated

   • +/- paracetamol, tramadol, gabapentin if required

   • proxymetacaine contraindicated—> delay corneal healing, decrease protective mechanism like tearinng and blinking

3. Topical lubricant

   • increase rate reepithelialisation

4. +/- single drop of atropine (pupal dilation)
   – Improves ‘reflex uveitis’
   – reduce tear production—> contraindicate if KCS

5. Protective collar

6. Recheck in 2-5 days

SCCED treatment: surgical

1. prep cornea prep the cornea with 1:50 povidone iodine solution

2. debribement of loose epithelium (mostly done in dogs, cats develop sequestrum easily esp with grid keratotomy

• Debride with cotton buds ~50% success

• Keratotomy (grid or punctate) ~80% success

• Diamond burr debridement ~80% success

• Superficial keratectomy

±soft contact lens in conjunction

recognising corneal perforation

• Acutely painful

• yelp in pain, keep eye completely closed

• Excessive ‘tearing’ or wetting of the face below ulcer

• Perforation site often plugged with clotted aqueous (+/- haemorrhage)

• iris Appears as tan, red or pigmented bulging mass at the centre of an ulcer

—>Refer as an emergency for corneal graft or enucleate

care in cotton bud debribement

• must remove all loose epithelium

• ulcer size increase is ok, dont worry

• normal epithelium should firmly attach

Superficial grid keratotomy

• 25G needle to produce superficial scratches in a grid pattern

• Scarring may result

Contraindicagion: grad keratotomy in cats

cats will often develop sequestrum post grad keratotomy

Diamond burr debridement

• Easy to use in a conscious patient

• Relatively ‘safe’ option

• Rarely, melting ulcer is a complication

Soft corneal bandage lens use in tx

• Improves comfort

• Reduces healing time

• Retention can be an issue

  • temporary tarsorrhaphy suture to improve if needed
    

contraindication for SCBL

stromal/ malacic/ infected ulcers

at least how long to is needed between debridement?

at least 7-10 days

describe SCCED tx in diagram