Common ocular conditions in horses 1 + 2 Flashcards
How would you manage an eyelid laceration?
- Flush – iodine if available
- Little debridement needed
- Need eyelid margin to be perfectly repaired
- Surgical repair
How is the prognosis of an eyelid laceration different depending on location?
- Lacerations of the lower eyelid have a better prognosis than those on the upper (as the upper spreads a lot more of the tear film)
- Worse prognosis on the medial side vs lateral as this is where the tear ducts are
Name some eyelid masses
- Sarcoid
- SCC (most common)
- Melanoma
- Lymphoma
Where is the most common site of growth for SCC?
Third eyelid
Name the 4 layers of the cornea
- Epithelium
- Stroma
- Descemet’s membrane
- Endothelium
What is the stroma made up of?
Collagen fibres
What are the clinical signs of ulcerative keratitis in horses?
Corneal ulcer:
- Pain
- Blepharospasm
- Epiphora
- Photophobia
How should superficial ulcers be treated?
Tend to heal with no complications if appropriate therapy
- Topical antimicrobial
- +/- topical atropine
- Healing rate approximately 0.6mm/day
- No corneal scar
How are deep ulcers treated?
Treatment for non-complicated deep ulcers same as for superficial but for a longer period of time.
Scarring likely
What is the term used to describe a melting ulcer?
Keratomalacia
Describe the pathophysiology of keratomalacia
Activation and/or production of proteolytic enzymes by:
- Corneal epithelial cells
- Leucocytes
- Microbial organisms (Pseudomonas)
How is keratomalacia treated?
Requires early aggressive therapy
- Topical Serum
- Topical EDTA
- Topical Acetylcysteine
- Topical Tetracycline or Doxycycline
- Systemic NSAIDs (Flunixin)
What is a descemetocele?
- Stoma has gone and the ulcer is down to the Descemet’s membrane
- At this point the eye is down to 4 layers of cells left
- High risk of rupture
- Deep crater
How are descemetoceles managed?
- Walls would stain with Fluorescein, center wouldn’t
- Wouldn’t be more painful that other ulcers
- Aggressive therapy necessary: same as for deep melting ulcers
- Surgical therapy may be necessary
What can occur secondary to an ulcer?
Stromal abscess
How does a stromal abscess occur?
Epithelium heals but the stroma is still damaged
How would a stromal abscess stain?
Fluorescein negative
How are stromal abscesses treated?
Medical therapy: appropriate antimicrobial therapy
Surgery may be required: debridement or corneal grafting techniques
Name the viral cause of viral keratitis
Equine herpes virus 2
How does viral keratitis present?
Multiple, superficial, white, punctate or linear (dendritic) opacities
Varying (normally high) degree of ocular pain
How is viral keratitis diagnosed?
Difficult to diagnose – Virus isolation and/or PCR
How is viral keratitis treated?
Topical Idoxuridine
Topical Trifluorothymidine
Topical Aciclovir / Ganciclovir
Topical Interferon γ
Topical corticosteroid?
How is fungal keratitis treated?
- Slow to resolve!
- Surgery (keratectomy ± conjunctival flap) usually necessary
- Signs usually deteriorate 24 hours after starting antifungal therapy due to massive death of fungus with a dramatic PMN response and secondary uveitis
Topical: - Miconazole
- Natamycin
- Fluconazole
- Itraconazole
How do immune mediated keratopathies present?
- Slow onset, not obvious at first
- Usually unilateral
- Slight ocular discomfort (no uveitis!)
- Vary from irregular corneal surface to deep bullae formation, vascularisation and oedema
