Corneal Disease Flashcards
(49 cards)
What is a corneal ulcer?
Any keratopathy with loss of epithelium exposing the underlying corneal stroma
Corneal ulcers are classified by depth (superficial, stromal, descemetocele, perforation) and cause.
What are common causes of corneal ulcers?
Common causes include:
* Trauma/abrasions
* Primary corneal pathogens (herpesvirus)
* Keratoconjunctivitis sicca
* Entropion
* Trichiasis
* Distichiasis
* Ectopic cilia
* Dermoid
* Eyelid agenesis
* Eyelid neoplasia or inflammation
* Foreign bodies
* Exposure keratitis
* Topical irritants
List includes both anatomical and environmental factors.
What clinical signs are associated with corneal ulcers?
Clinical signs include:
* Lacrimation
* Blepharospasm
* Photophobia
* Conjunctival hyperaemia
* Corneal oedema
* Miosis
* Aqueous flare
These signs indicate irritation and inflammation of the cornea.
What test should be performed to rule out keratoconjunctivitis sicca (KCS)?
Schirmer tear test (STT)
unless there is imminent risk of perforation or excess tearing is observed
What is the primary management step for corneal ulcers?
Identification and removal or correction of the cause
This is crucial for healing; otherwise, ulcers may progress.
Why are topical antibiotics indicated for corneal ulcers?
Disruption of epithelium predisposes corneal stroma to infection
Antibiotics help prevent secondary infections in the cornea.
What agents can be used to manage pain associated with corneal ulcers?
why
Topical mydriatics and cycloplegics (e.g., atropine, cyclopentolate)
- pain can cause reflex neurogenic anterior uveitis, which causes miosis, increased protein levels in aqueous humour (aqueous flare), and exacerbates pain
These agents help alleviate discomfort from ciliary muscle spasms.
Contraindicated in KCS as they reduce tear production
Why are corticosteroids contraindicated in the treatment of corneal ulcers?
Can topical NSAIDs be used?
- Corticosteroids: delay corneal healing, predispose to infection and potentiate enzymatic destruction of the cornea, so always contraindicated.
- NSAIDS: may be used but can also delay healing and have been associated with rapid progression of infected ulcers in humans so are contraindicated in infection. Discretion advised
if moderate to severe uveitis accompanies an ulcer then systemic NSAIDS can be used
How are eye drops used if multiple medications are to be applied
- multiple drops, period of at least 5 - 10minutes in between.
- drops and ointments: onitment after drops or drops given at least 2 hours after the onitment.
What are superficial ulcers characterized by?
Fluorescein stain retention and relatively clear defects in the cornea
The walls of the defect are only as thick as the corneal epithelium.
summarise the treatment for superficial ulcers?
- Topical AB, Chloramphenicol q6 -8 or triple AB wit polymixin B, neomycin and bacitracin.
- Atropine suphale single dose or Q24 for up to 2 days, if pupil miotic and eye is painful (or cyclopentolate)
- systemic analgesia maybe
- lubrication
- elizabethan collar
- deal with kcs if underlying
if moderate to serve uveitis present systemic NSAIDS used.
Treatment should also address the underlying cause of the ulcer.
What should be done if KCS is the cause of the ulcer?
Appropriate treatment for KCS should be started
Topical atropine must be avoided in these cases.
What additional treatments/diagnostics are considered when corneal ulcers are present in the cat
- May have viral (FHV-1) aeitology.
- if consistent then tolical antiviral should also be added (ganciclovir, q 4 - 6) or oral famciclovir.
- antiviral durgs are administrered for afew days to a week after clinical remission and never tapered (promotes resistance.
What is a stromal ulcer?
How are they diagnosed, are there any additional tests that are benefit
- Deeper ulcer extending to the stroma
- still diagnosed by staining but may also be appreciated grossly.
- frequently associated with infection (gelatinous appearance).
- Cytology using a cytrobush, blunt end of scapel or cotton bud allows rapid identification of organisms.
careful handling needed espec if taking samples for cytology on an ulcer that is melting
what antibiotic therapy is appropriate for stromal ulcer
- should be based on cytology and culture
- Broad spectum intially eg a late generation fluroquinolone alone. or combonation therapy with an early generation fluroquinolone (ofloxacin) or aminoglycoside in addition to chloaphenicol or the triple AB therapy used for superficail ulcers.
What is the treatment for progressive deep stromal ulcers?
Aggressive antibiotic therapy and antiproteinase-anticollagenase treatment
This is important to prevent further corneal destruction.
What is the reason for the application of serum or plasma drops to progressive stromal ulcers?
- some bacteria, inflammatory cells and damaged corneal stromal or epithelial cells produce collagenases and proteases.
- leads to rapid destruction (melting) of the cornea.
- serum or plasma act as antiproteinases.
- NB high albumin levels limit the penetration of topical antibiotics so these should be applied last and at least 10min after the last AB
instiled avery 1 -2 hours initially in progessive ulcers and then the frequency reduced to 4-6. useful to add EDTA
is systemic use of NSAIDS indicated in stromal ulcers, why?
- normally yes
- reduce corneal inflammatory cell infiltration and associated corneal loss (anti collagenases, proteases).
- Treat pain caused by reflex anterior uveitis
Are systemic antibiotics useful in the management of corneal ulcers
- usually not because the cornea is avascular.
- may be useful in vascularised corneas where you would select doxycyline 5mg/kg Q 12 for its additional antiinflammatory and immunomodulatory effects
when and what surgical treatment is indicated for treatment of stromal ulcers
- when the leasion extends more than 50% the depth of the cornea or is rapidly progressive despite aggressive therapy.
- corneal grafts, corneoconjunctival transposition and grafting of biomaterials
What is a descemetocele?
A deep corneal ulcer where the epithelium and stroma are destroyed, lined by Descemet’s membrane and corneal endothelium only.
- The edges have stain uptake because the stroma is exposed but the centre of the lesion will not have any stain uptake.
Indicates imminent danger of corneal perforation.
What is the recommended treatment for a descemetocele?
- careful handling of the animal when restraining to avoid perforation.
- topical ab as per deep stromal ulcers if tolerated ideal, but delay if struggling (risk of rupture)
- cage rest and e collar
- avoid ointments as mineral oil and petroleum are irritating
- surgical emergency, CCT preferred but small lesions may be repaired with a conjuncyival graft (less structural integretity so not ideal)
Globe prog good if surgical repair without cmplications. Visual prognosis depends on extent of corneal disease and the type of graft used
What is the role of cytology in the assessment of corneal ulcers?
Allows rapid identification of bacteria, fungal hyphae, and the type of inflammatory process
This guides therapy decisions.
How should topical serum or plasma be applied in the treatment of melting ulcers?
Applied last, 10 minutes after other topical treatments
Serum or plasma has high albumin concentration that limits antibiotic penetration.
