Equine corneal disease Flashcards
What are the main corneal disease in the horse?
Ulcerative
* Infectious (Viral, Bacterial, Fungal)
* Non infectious
* Traumatic
* Eosinophilic keratitis
* Keratopathies
* Iatrogenic (radiation, chemical, etc)
* Tear deficiency
Non-ulcerative
* Non-infectious (Immune-mediated)
* Infectious
* Stromal abscess
* Parasitic
What are the causes of ulcerative keratitis?
Trauma
* Scratches
* Foreign bodies
* Blunt trauma
* Chemical
Infections
* Bacterial
* Viral
* Fungal
Incomplete eyelid closure
What is the clinical presentation of Ulcerative keratitis aka corneal ulceration?
Usually painful but not always
* Blepharospasm, ptosis
* ±Conjunctival swelling
* Conjunctival inflammation
* Epiphora/discharge
Corneal Opacity
Secondary uveitis
* Myosis
* Empyema/hyphema/synaechiae
* Iris prolapse
* Fibrin in anterior chamber
How is ulceratice keratitis diagnosed?
What is the management?
What should never be used?
Ophthalmic examination
- Observation + menace
- Sedation/Palpebral NB
- Direct ophthalmoscopy
Fluorescein Stain - Blue light
Rose Bengal - Green light
Management
- debriding - removal of non-adherant tissue
- pain management
- antimicrobials
NEVER steroids
What is a Grid/punctate keratotomy?
Why is it done
drand needle from periferay to centre of the ulcer - drags healthy epithelial cells to the centre
also scrathces the stroma to expose healthy stromal cells
* Just through basement membrane
* Exposes stromal collagen
* Promotes epithelial stronger attachment
* Takes longer (1-3 weeks) but more likely to heal
Why can corneal cyctology be helpful?
to look for fungal hyphae immediately (fungal culture is not very successful and take long time) - not common in the uk - for identification of fungal keratitis
How long does it take of corneal ulcers to heal?
Epithelium turn over – 7 days
Healing 0.6mm/day –
Exp ulcers removing 1/3 thickness stroma heal in ~11 days
can take several weeks
What antibiotic is most commonly used with cornela ulceration?
chloramphenicol
What pain mangement is used for painful eyes?
Anti-inflammatories
* Flunixin meglumine IV
* Paracetamol PO
* Opioids?
* Topical anti-inflammatories
Control of myosis (inflammation causes contraction, spasm of iris causes pain so need to dilate)
* Topical atropine until mydriasis then as required to maintain
Dark environment
Mask
± Contact lenses
± Lubricants
What treatments fo rcorneal ulcers can be used in a hospital setting?
What is the thought process behind there use?
Autologous serum - application every 2h
* Anti-collagenase activity
* Antibodies
* Nutrients
* Growth factors, fibronectine and vitamins
* Max for 8 days in fridge
EDTA - application every 2h
* Synergistic antiprotease action with serum
Acetylcysteine
* Antiprotease but interferes with mucous tear-film layer
Doxycycline
* Antiproteolytic
* Immunomodulatory
What procedure can be done to make topical products easier to administer into horses eyes?
Sub-palpebral lavage system
Administration at the withers
Flush with air vs priming
Combine with infusion pumps
What are the two types of viral keratitis?
What virus has been accosiated with this?
How is it diagnosed?
Type I – Dendritic pattern
Type II – Multifocal pattern
* has been accosiated with, EHV-1,2 & 4 – EHV-2 main cause of keratitis - but main cuase is unknown
Dx: appearance - Pain, Epiphora and, blepharospasm, Usually unilateral
* qPCR of conjunctival swab but positive also in normal horses
What type of viral keratitis is this?
Type I - dendritic pattern
What type of viral keratitis is this?
Type II – Multifocal pattern
What is the treatment for viral keratitis?
Idoxuridine for 7 days
* every 2h for 2 days then every 6h
Galacyclovir, Acyclovir (II), trifluridine (I, II), vidarabine
* Efficacy not fully evaluated
Cyclosporin A (II)
When does fungal keratitis occur?
What is the treatment?
How long does it take fix?
Likes humid hot weather - Less common in UK
- Azole antifungals
- Voriconazole
- Clotrimazole?
- Subconjunctival Amphotericin B
- Prophylactic antimicrobials
- EDTA, serum, tetracyclines
Weeks to months (average is 35 days)
Clinical efficacy difficult to assess
What is condition is shown here??
What is the treatment?
**Eosinophilic keratitis - **
White Corneal plaques
* Eosinophil, Mast cells, Lymphs, neutrophils
Stromal cellular infiltrate
Pruritic
Treatment
Debridement
+ Calcineurin inhibitors
± steroids
± antihistamines
What is shown here?
Stromal abcess
What is the treatment for superficial and deep corneal abscesses?
Superficial
* Topical antimicrobials/antifungals (SPL! 4-6 weeks)
* Mydriatic drugs (atropine)
* NSAIDs (systemic ±topical)
* Debridement (±)
Mid to Deep
* Surgical
* Debridement/deep lamellar keratoplasty
* Conjunctival graft
* Don’t completely heal until vascolarised
What is the presentaiton of Immuno-mediated Keratitis (IMMK)?
What is the treatment?
**Presentation **Some or all of:
* Neovascularisation
* Oedema
* Cellular infiltration
* Anterior uveitis
* Transient ulceration
* Minimal discomfort
Treatment
* Dexamethasone
* Calcineurin inhibitors
* Cyclosporin A
* Tacrolimus
* Doxyciclyne
* (Sirolimus)
Sometimes they can ulcerate
* NO CORTICOSTERIODS
* Treat like an ulcer until no uptake
What type of IMMK is the an example of?
Describe what you can see
Chronic Superficial Keratitis
Superficial vascularization
Arborification and oedema
What type of IMMK is the an example of?
Describe what you can see
Epithelial keratopathy
Absent vascularization Irregular clumps of epithelial oedema
What type of IMMK is the an example of?
Describe what you can see
Endothelitis
Faint endothelial vessels
Mild oedema
When should you refer corneal conditions?
Positive Seidel test, iris prolapse
Severe uveitis
Melting (deviation of normal corneal contour)
Requires debridement and you are not happy to debride
Deteriorates despite treatment
Horse difficult to medicate (need SPL?)
If eye non-visual – consider enucleation
US very helpful in cases with complete corneal opacity
what eye conditions can surgery be used ot treat?
- Perforation
- Iris prolapse
- Positive Seidel test
- Melting
- Descemetocoele
- No response to medical tx
(Grafts vs Enucleation
Temporary tarsorraphy
Transplants/grafts – tertiary referral)
