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Y4 Farm - Miscellaneous > Ophthalmology > Flashcards

Ophthalmology Flashcards

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1
Q

How should sheep/goats be restrained for an ophthalmic exam?

A
  • backed into corner and head restrained by assistant or tipped so sitting on rump
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2
Q

How should camelids be restrained for an ophthalmic exam?

A
  • halter
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3
Q

How should cattle be restrained for an ophthalmic exam?

A
  • head catch and crush with halter to pull head laterally
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4
Q

How would you apply topical anaesthesia to the eye prior to ophthalmic exam?

A
  • 1% procaine hydrochloride instilled topically to cornea and conjunctival surface
  • 1-2 drops = 10-20 mins anaesthesia
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5
Q

How might you facilitate opening of the eyelids prior to ophthalmic exam?

A
  • procaine infiltrated around auriculopalpebral nerve as it crosses zygomatic arch
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6
Q

What should be your first examination during ophthalmic exam?

A
  • determine whether the animal can see
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7
Q

Signs of visually impaired animals?

A
  • startled
  • run into other animals and objects
  • reluctant to move
  • fail to stay with the herd
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8
Q

How can you determine whether the animal can blink?

A
  • touch periocular skin nasally and temporally to stimulate palpebral reflex
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9
Q

What does a failure to blink indicate?

A
  • deficit in sensation (trigeminal nerve V) or deficit in motor innervation (cranial nerve VII - facial)
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10
Q

Is PLR test of vision?

A

no - if animal blind and PLR absent then lesion located within retina, optic nerve, optic chiasm or optic tract

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11
Q

How should pupils appear?

A
  • equal size
  • symmetrical
  • appropriately sized for ambient lighting conditions
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12
Q

Direct PLR?

A
  • as light directed into eye, pupil should constrict
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13
Q

Indirect PLR?

A
  • as light directed into eye, contralateral pupil should also constrict due to crossing over of optic nerves through optic chiasm
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14
Q

How does normal cornea appear?

A
  • smooth, transparent, glossy with reflective surface and no BV
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15
Q

What do fine, branching blood vessels that originate from conjunctiva signify?

A
  • chronic irritation or ulceration of surface
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16
Q

What do short, straight, deep vessels that originate at limbus signify?

A
  • deep keratitis or intra-ocular disease (anterior uveitis or glaucoma)
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17
Q

What might pink to red raised lesions of corneal surface signify?

A
  • granulation tissue + normal corneal healing after trauma or deep ulceration
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18
Q

What might white opacities on the cornea signify?

A
  • presence of lipid, calcium or fibrosis
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19
Q

Instillation of what can aid identification of corneal ulceration?

A
  • fluorescein dye -> normal cornea shouldn’t take this up
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19
Q

What might beige or milky appearance of cornea signify?

A
  • inflammatory cells within stroma, especially if have ulceration
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20
Q

What might bluish-grey steamy appearance of cornea signify?

A
  • corneal oedema
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21
Q

What should you check for regarding eyelids?

A
  • smooth lid margin
  • evert for inspection of palpebral conjunctiva
  • should be freely movable and close in response to digital pressure
  • any irregularities may indicate SCC
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22
Q

What should you check for regarding tear production?

A
  • normal secretion = moist ocular surface
  • ocular surface dry then use Schirmer tear test for 1 min to determine tear production
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23
Q

Normal Schirmer tear test?

A
  • > 20mm/min
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23
Abnormal anterior chamber - findings
- presence of blood (hyphema), fibrin, increased protein (flare) or inflammatory cells (hypopyon)
24
Entropion signalment
- newborn lambs
25
What is entropion?
- turning in of the eyelids
25
Entropion tx
mild - roll down skin immediately below lower eyelid Severe - subconjunctival injection of antibiotic - 1ml procaine penicillin injected into lower eyelid using 21G needle - deposited bump effectively everts eyelid and holds it away from surface of the eye (also treats and controls any associated bacterial infection) OR insertion of Michel clips - thin metal strips placed in skin at right angles to palpebral fissure and closed - pulls lower eyelid down + away. OR surgical
26
What can occur if entropion is left untreated?
- secondary corneal ulceration, keratitis and eventual blindness
27
Clinical presentation of IBR in eyes
- epiphora - blepharospasm - conjunctivitis - keratitis with corneal oedema and cloudiness - granulation tissue and neovascularisation occurs 3-4d after onset of IBK
27
Advantage of Michel clips over subconjunctival injection of procaine penicillin
- single operator required but lack of concurrent antibiotic tx
28
IBR tx
- antibiotics + NSAIDs - systemic: florfenicol and oxytet - topical over several days: cloxacillin ointment and potentiated penicillin subconjunctival injection
29
Where are corneal lesions associated with IBR typically located?
centrally (FB = any location) and range from small and white to large + ulcerating if advanced full thickness ulceration = risk
29
IBR transmission
- contagious - close proximity of cattle + flies can spread - troughs + handlers hands = other vectors - disease spreads through group within a few weeks
30
IBR prevention
- fly control - vaccination
31
What can infection with listeria monocytogenes cause?
- anterior uveitis (also known as silage eye)
32
Pathogenesis of listeria monocytogenes causing silage eye
- listeria in dangerous quantities in silage not fermented sufficiently to kill bacteria - often many animals in herd affected with feeding new silage batch
33
CS of listeria monocytogenes (silage eye)
- profuse discharge from the eye - epiphora - cloudy discolouration of eye surface - bulges of iris - unwilling to open - aversion to light - 2-3 days = bluish opacity
33
Silage eye - prevention
- produce low risk silage for ruminants by ensuring minimal soil contamination - pay attention when bailing and wrapping silage to ensure appropriate fermentation conditions - minimise exposure of silage to air through punctures - make bales or clamp silage with shorter chop so cows don't have to bury heads to feed
33
Tx for silage eye
- bulbar sub-conjunctival admin of antibiotics + NSAIDs
34
What other CS can infection with listeria cause in cattle and sheep?
- abortion - neurological signs
35
Detection of corneal ulcers
- visual observation + fluorescein
36
Tx for ulcers up to 50% depth
- topical or subconjunctival antibiotics plus collagenase inhibitors (EDTA/oxytet) - NSAIDs for analgesia - should heal in 5-10 days
36
Tx for ulcers >50% depth or progressive
- surgical intervention - tarsorrhaphy (suturing eyelids together) - sub-palpebral lavage system inserted - enucleation - healing occurs in 2-6 weeks
37
What are the most common type of neoplasia affecting the eye?
- SCC -- occurrence likely increases with increased exposure to UV light
38
Common sites for SCC of eye
- third eyelid - junction between sclera and cornea - lower eyelid
38
Which cattle are most affected by ocular neoplasia?
- those with little periorbital pigmentation
39
Final carcinoma appearance for SCC
- nodular and pink
39
Early SCC lesion appearance
- white nodules or plaques that progress to wart-like proliferations
40
4 stages in development of SCC
1. plaque 2. keratoma - skin growth coated with eye secretions 3. papilloma 4. carcinoma
40
SCC diagnosis
- CS usually but can be confirmed by biopsy - impression smear may give indication but severe inflammation will give similar cytological appearance - regional LN checked for mets
41
SCC tx
- surgical excision of all abnormal tissue within wide surgical margin of 2-3mm - may necessitate partial keratectomy for corneal lesions - enucleation best for eyelid lesions
42
Indications for enucleation
- trauma - severe exophthalmos (protrusion) - severe perforating ulcer - glaucoma - severe IBK with rupture of globe - congenital defects - neoplasia
43
Cow sedation for enucleation
- small volume of xylazine IM or IV
44
4 point LA block work for anaesthesia of eye prior to enucleation
- long needle to go round back of eye using procaine: insert LA in lower, upper, medial and lateral canthus of eye - around 15ml
44
Anaesthesia protocol for enucleation
- meloxicam pre-op - LA subcut around soft tissue area using 18G needle - 4 point block to block the back of the eye OR retrobulbar block
45
Retrobulbar block work for anaesthesia of eye prior to enucleation?
- deposit 35ml of lignocaine hydrochloride into retrobulbar cone - or peterson nerve block: 12cm needle sc between frontal and temporal process of zygomatic bone + directed along zygomatic arch depositing 10-20ml lignocaine hydrochloride
46
Enucleation prep
- full clip + surgical scrub - suture eyelid closed
46
What should you remove prior to removal of globe?
- 3rd eyelid
47
What should you clamp prior to removing globe?
- optic nerve + blood vessels
47
Common congenital ocular disorders in camelids
- nasolacrimal duct disorders
48
How to close following enucleation?
- leave dead space empty (fills with haematoma that will go away) - create tight seal of eyelids with nonabsorbable suture to evert skin + contain haematoma - pressure bandage or antibiotics dependent on compliance - remove suture 10-14 days post-op
48
CS of congenital nasolacrimal duct disorders
- wet face - mucupurulent ocular discharge caused by secondary dacryocystitis (inflammation of lacrimal sac)
49
Examples of systemic disease with ocular involvement
- septicaemia resulting in hypophyon - head and eye form of MCF - IBR - Endotoxaemia with inject conjunctiva - BVD causing cataracts - bleeding disorders eg bracken poisoning resulting in hyphaemia - blindness caused by central lesions
50
With systemic disease causing ocular lesions, what would you expect?
- bilateral lesions + additional non-ocular signs in particular pyrexia
51
Corneal trauma in camelids - causes
- fighting, FB, recumbency following prolonged anaesthesia, tick paralysis, lack of PT in crias - often deep but resolve with tx
51
CS of conjunctivitis in camelids
- mild squinting - conjunctival hyperaemia - epiphora
52
Cause of conjunctivitis in camelids
- irritation - self limiting as long as offending agent eg dust, FB removed
53
What is a common sequelae of systemic disease in camelids?
- uveitis
54
What is the most common abnormality of camelid lens?
- cataract
55
What could uveitis be secondary to in camelids?
- deep ulcerative keratitis - lens-induced uveitis - trauma - infectious disease eg equine herpesvirus type I
56
CS of uveitis in camelids
- mild squinting - epiphora - aqeuous flare

Y4 Farm - Miscellaneous (22 decks)

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