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Michaelmas 5th year > Equine ophthalmology > Flashcards

Equine ophthalmology Flashcards

1
Q

What is the location of lacrimal punta in horses

A

Dorsal and ventral

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2
Q

Where do drained tears go

A

Through canaliculi into nasolacrimal duct and out nasal ostium (next to pigmented/unpigmented skin in nose)

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3
Q

What are vibrissae

A

Very sensitive hairs
3 or 4 found dorsomedial to the upper lid
8-12 found ventral to lower lid

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4
Q

What are corpora nigra

A

Proliferation of iris tissue
More so dorsally than centrally

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5
Q

What is different about examining the iridocorneal angle in horses than cats/dogs

A

Canbe examined directly rather that needing to use a gonioscope

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6
Q

Where do we block the frontal nerve

A

Supraorbital fossa

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7
Q

Where do we block the auriculopalpebral nerve

A

Zygomatic arch

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8
Q

What do we block for eyelid akinesia

A

Auriculopalpebral nerve CN VII at zygomatic arch

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9
Q

What do we block for upper eyelid desensitisation

A

Frontal nerve; branch of trigeminal nerve

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10
Q

Characteristics of equine fundus

A

Paurangiotic with many vessels emanating short distance from the optic nerve

Tapetum is dorsal and fibrous

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11
Q

What are stars of winslow

A

Dots seen in the fibrous tapetum of horses which are end on choroidal capillaries

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12
Q

Why do we percuss sinuses during equine opthalmology exam

A

To check for space occupying lesions altering normal percussion

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13
Q

features of the menace response

A

Learned reflex so not present < 2 weeks old
Sensory is optic nerve, motor is facial nerve
+ involves visual cortex

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14
Q

Which reflex is a true test of vision

A

Menace reflex

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15
Q

Pupillary light reflex components

A

SEnsory = optic (II)
Motor = oculomotor (III)
No visual cortex involvement

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16
Q

Dazzle reflex components

A

Sensory = optic (II)
Efferent = facial (VII)
Doesn’t involve visual cortex = subcortical reflex

Does test retinal function

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17
Q

Palpebral reflex components

A

Sensory is trigeminal (V)
Motor is facia (VII)

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18
Q

What do we use to achieve mydriasis for ophthalmic examination

A

Tropicamide 1% - takes 10-20 mins to work

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19
Q

How does indirect ophthalmoscopy work

A

One operator holds lens close to horses eye and other holds light source near examiner
They function as a unit

20
Q

Qualities of indirect ophthalmoscopy

A

Virtual image which is inverted and reversed
Larger field of view so easier detectino
Safer
Use 20D lens

21
Q

Monocular vs binocular indirect ophthalmoscopy

A

Binocular uses head mounted light source so have two eyes and can get depth perception

22
Q

Qualities of direct ophthalmoscopy

A

Upright image
Greater magnification

23
Q

What do concave vs convex lenses on a direct opthalmoscope do

A

Convex = +ve lenses; bring position of focus closer to you to look at more anterior things

Concave = -ve lenses; brings focus further away to look at more posterior things

24
Q

What dioptre setting do we use for distant direct ophthalmoscopy

A

0 dioptres

25
Q

What dioptre setting is the fundus in focus at

A

Between 0 and -2D

26
Q

When to avoid tonometry

A

Fragile eyes e.g laceration, deep corneal ulcer due to risk of rupture

27
Q

What type of tonometer is tonovet

A

REbound

28
Q

What is a subpalpebral lavage system

A

Used to apply topical mediations to the eye in head shy horses or where frequent application needed and not easy to do

Involves placement of a footplate under upper or lower eyelid

29
Q

How to repair eyelid lacerations

A

Close in 2 layers; first deep subconjunctival layer then skin layer

30
Q

What is the antidromic reflex

A

Trigeminal stimulation feedback no the uveal tract in uveitis
See in corneal ulceration

31
Q

What to use with complicated corneal ulcers

A

Antibiotics with good gram -ve cover which is bacteriocidal
Anticollagenase if evidence of melting ulcer

Atropine and NSAIDs

32
Q

What mightmultifocal white epithelial opacities on a horse cornea be a sign of

A

Equine herpes virus keratitis due to EHV-2

33
Q

What treatment do we use for EHV-2 keratitis

A

Topical antivirls e.g gangiclovir

34
Q

What is eosinophilic keratitis

A

Immune mediated disease
treat with topical corticosteroids

35
Q

Where in the eye might we get squamous cell carcinoma

A

All components of exterior globe/eyelids
i.e eyelids, conjunctiva, cornea, orbit

36
Q

What is chorioretinal scarring

A

Depigmentation of the fundus related to previous inflammation e.g from equine recurent uveitis

May present as bullet holes or butterfly lesions

37
Q

What is anterior vs posterior vs panuvieitis

A

i) Anterior uveitis: iris, ciliary body, anterior chamber
ii) Posterior uveitis: vitreous, retina, choroid
iii) Panuveitis: all areas of uveal tract affected

38
Q

Treatment of equine uveitis

A

Topical corticosteroids, NSAIDs, systemic NSAIDs
Atropine
May implant cyclosporin implants under choroid in recurrent cases

39
Q

WHat is the end stage appearance of uveitis

A

small shrunken globe = phthisis bulbi

40
Q

What is phthisis bulbi

A

Small shrunken bulb due to end stage uveitis

41
Q

What is the most common cause of blindness in the horse

A

Equine recurrent uveitis

42
Q

What is the aetiology of equine recurrent uveitis

A

Immune mediated

ASsociation with leptospira infection, with systemic illness

43
Q

Acute stage signs of uveitis

A

pain, lacrimation, blephrospasm, eyelid oedema, perilimbal corneal vascularisation, mioisis, inflammatory debris in anterior chamber (fibrin, pus i.e hypopyon), vitritis (clouding of vitreous), hypotony

44
Q

Chronic stage signs of uveitis

A

less pain, darkened iris, corneal oedema, adhesions b/w iris and lens (= posterior synechiae), corpora nigra atrophy, corneal mineralisation (calcific band keratopathy), cataract, lens luxation/subluxation (fibres that hold it in place degrade), chorioretinal scarring, glaucoma

45
Q

What cause of keratitis typically has a frosted appereance

A

Fungal keratitis

46
Q

What can present as unilateral corneal odema, stromal fibrovasculariation

A

Immune medaited keratitis
Treat with corticosteroids and cyclosporin

Michaelmas 5th year (41 decks)

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