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Y4 EQ - Ophthalmology/Neurology > Common ocular conditions in horses 1 + 2 > Flashcards

Common ocular conditions in horses 1 + 2 Flashcards

1
Q

How would you manage an eyelid laceration?

A
  • Flush – iodine if available
  • Little debridement needed
  • Need eyelid margin to be perfectly repaired
  • Surgical repair
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2
Q

How is the prognosis of an eyelid laceration different depending on location?

A
  • 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
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3
Q

Name some eyelid masses

A
  • Sarcoid
  • SCC (most common)
  • Melanoma
  • Lymphoma
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4
Q

Where is the most common site of growth for SCC?

A

Third eyelid

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5
Q

Name the 4 layers of the cornea

A
  • Epithelium
  • Stroma
  • Descemet’s membrane
  • Endothelium
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6
Q

What is the stroma made up of?

A

Collagen fibres

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7
Q

What are the clinical signs of ulcerative keratitis in horses?

A

Corneal ulcer:
- Pain
- Blepharospasm
- Epiphora
- Photophobia

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8
Q

How should superficial ulcers be treated?

A

Tend to heal with no complications if appropriate therapy
- Topical antimicrobial
- +/- topical atropine
- Healing rate approximately 0.6mm/day
- No corneal scar

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9
Q

How are deep ulcers treated?

A

Treatment for non-complicated deep ulcers same as for superficial but for a longer period of time.
Scarring likely

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10
Q

What is the term used to describe a melting ulcer?

A

Keratomalacia

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11
Q

Describe the pathophysiology of keratomalacia

A

Activation and/or production of proteolytic enzymes by:
- Corneal epithelial cells
- Leucocytes
- Microbial organisms (Pseudomonas)

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12
Q

How is keratomalacia treated?

A

Requires early aggressive therapy
- Topical Serum
- Topical EDTA
- Topical Acetylcysteine
- Topical Tetracycline or Doxycycline
- Systemic NSAIDs (Flunixin)

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13
Q

What is a descemetocele?

A
  • 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
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14
Q

How are descemetoceles managed?

A
  • 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
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15
Q

What can occur secondary to an ulcer?

A

Stromal abscess

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16
Q

How does a stromal abscess occur?

A

Epithelium heals but the stroma is still damaged

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17
Q

How would a stromal abscess stain?

A

Fluorescein negative

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18
Q

How are stromal abscesses treated?

A

Medical therapy: appropriate antimicrobial therapy
Surgery may be required: debridement or corneal grafting techniques

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19
Q

Name the viral cause of viral keratitis

A

Equine herpes virus 2

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20
Q

How does viral keratitis present?

A

Multiple, superficial, white, punctate or linear (dendritic) opacities
Varying (normally high) degree of ocular pain

21
Q

How is viral keratitis diagnosed?

A

Difficult to diagnose – Virus isolation and/or PCR

22
Q

How is viral keratitis treated?

A

Topical Idoxuridine
Topical Trifluorothymidine
Topical Aciclovir / Ganciclovir
Topical Interferon γ
Topical corticosteroid?

23
Q

How is fungal keratitis treated?

A
  • 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
24
Q

How do immune mediated keratopathies present?

A
  • 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
25
Q

How is an immune mediated keratopathy treated?

A

Medical: topical corticosteroid, cyclosporine A or doxycycline
Surgical: keratectomy, cyclosporine A implant

26
Q

How will an immune mediated keratitis stain?

A

Potentially faint uptake of stain - not an ulcer but shows the tissue is not healthy

27
Q

Which structures of the eye are inflamed with uveitis?

A

Iris
Ciliary body
Choroid

28
Q

What happens if uveitis is left untreated?

A

Blindness

29
Q

Describe the aetiology of uveitis in horses

A
  • Primary or secondary to other eye disease (ie eye ulcer) or systemic disease (ie Rhodococcus)
  • Strong immune mediated component
  • Leptospira spp. involved in a large number of cases in mainland Europe and USA (UK less so)
  • Recurrence episodes likely
30
Q

List the clinical signs of anterior uveitis

A
  • Pain: blepharospasm and epiphora
  • Chemosis: red eye
  • Constricted pupil
  • Aqueous flare: milky appearance of anterior chamber
  • Blood (hyphaema), pus (hypopyon) or fibrin in anterior chamber
  • Cant see the inside of the eye
31
Q

List the clinical signs of posterior uveitis

A
  • Subtle!
  • Pain variable (often very mild)
  • Vitritis
  • Retinal changes
  • Typically diagnosed late in the course of the disease
32
Q

How is uveitis treated?

A
  • Topical corticosteroid (if no ulcer present)
  • Topical NSAID? (if ulcer present)
  • Topical antimicrobial?
  • Topical atropine (c/4h until pupil dilates)
  • Systemic NSAID: Flunixin > Phenylbutazone
33
Q

What is the danger of using atropine?

A

Colic

34
Q

Which surgical options are available for uveitis?

A
  • Suprachoroidal Cyclosporine A implant
  • Pars plana vitrectomy
  • Enucleation
35
Q

List the long term complications of uveitis

A
  • Atrophy granula iridica
  • Synechiae (adhesions)
  • Cataracts
  • Glaucoma
  • Retinal pathology
  • Blindness
  • Phthisis bulbi
36
Q

Define the term cataracts

A

Any opacity of the lens

37
Q

How can cataracts be classified?

A
  • Acquired or secondary cataracts (uveitis, trauma, tumour)
  • Developmental opacities, including congenital cataracts
38
Q

Describe the ophthalmic exam of the lens

A
  1. Retroillumination
    - Use light reflected from the tapetum with focal light source/direct ophthalmoscope at arm’s length distance directing the light to obtain a bright tapetal reflex
    - Opacities appear dark
  2. Direct focal illumination (= transillumination)
    - Direct beam light at 45 degree angle into the lens
    - Cataracts appear white
39
Q

How is cataracts treated?

A
  • Most of them do not require treatment (treat primary cause if secondary)
  • Aspirin?: 30mg/kg/day PO
  • Surgery can be performed in young foals (before 4 months of age)
40
Q

What is the normal IOP of a horse?

A

normal 15- 30mm/Hg

41
Q

What is glaucoma?

A

Increased intraocular pressure

42
Q

Is glaucoma common or uncommon in horses? Why?

A

Relatively uncommon in horses.
2 methods of draining the aqueous humour - Conventional (60%) + unconventional (40%) aqueous humour drainage

43
Q

List the clinical signs of glaucoma

A
  • Hydrophthalmos or buphthalmos
  • Corneal oedema
  • Corneal striae
  • Lens luxation
  • Blindness
44
Q

What do corneal striations represent?

A

Where the Descemet’s membrane is torn

45
Q

How is glaucoma diagnosed?

A

CS
Tonometry
US

46
Q

Describe the medical treatment options for glaucoma

A
  • Carbonic anhydrase inhibitors: topical (dorzolamide) and/or systemic (acetazolamide)
  • Beta-blockers: timolol (topical)
  • Anti-inflammatories: NSAIDs and/or corticosteroids, topical and/or systemic
  • Prostaglandins derivatives: contraindicated in horses!!
47
Q

Describe the features of the fundus

A
  • Tapetal region with stars of Winslow
  • Retinal vessels
  • Optic nerve
  • Non-tapetal region
48
Q

How does the optic nerve appear in horses?

A

Oval – Round(ish) in foals
Salmon-pink
3-5mm vertically and 5-8mm horizontally

49
Q
A

Y4 EQ - Ophthalmology/Neurology (4 decks)

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