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Equine (fourth year) > Ophthalmology > Flashcards

Ophthalmology Flashcards

1
Q

what is the outmost layer of the eye?

A

sclera

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2
Q

what is the function of the sclera?

A

fibrous capsule that maintains the eyes shape

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3
Q

what structure is found on the dorsal surface of the iris?

A

granula iridica

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4
Q

what is the blue/grey structure found on the medial and lateral aspect of the eye?

A

pectinate ligament attachment

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5
Q

what dyes can be used for eye examination?

A

fluorescein
rose bengal

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6
Q

what is a pupil dilator called?

A

midriatic drug

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7
Q

what midriatic drug is commonly used for eye examination?

A

tropicamide

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8
Q

what should the lens of an ophthalmiscope be set to for distant direct ophthalmoscopy?

A

0

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9
Q

what is the disadvantage of using a direct ophthalmoscope to examine the retina?

A

only shows a tiny portion of it - have to map retina in your head

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10
Q

what is a slit lamp used for?

A

highlights the areas of refraction, can help to localise where lesions are by where they are in relation to the refracted areas (find depth of lesions)

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11
Q

what are the areas of the eye where light is refracted?

A

cornea
front of lens
back of lens

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12
Q

what is assessed first on an optic exam which would determine eye pain?

A

drooping/change of eyelid from the front of the horse

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13
Q

before sedating the horse what part of the eye exam should be done?

A

ocular reflexes

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14
Q

what ocular reflexes are performed as part of an eye examination?

A

PLR
dazzle
menace response
palpebral reflex
corneal reflex

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15
Q

where is the opening of the nasolacrimal duct in horses?

A

floor of the nose (roof in donkeys) - can see and catheterise

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16
Q

what nerve block is used for the eye examination?

A

auriculopalpebral
(frontal for sensory)

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17
Q

what is the use of fluorescein for the examination of the eye?

A

stains the corneal stroma - so identifies epithelial damage

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18
Q

how will fluorescein highlight different types of ulcers?

A

superficial - sharp edges with no epithelial under-run
indolent - epithelial under-run
deep stromal - intense staining with stain migration
descematocele - intense staining of walls with migration

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19
Q

what are the types of eye ulcer?

A

superficial, indolent, deep stroll, descematocele

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20
Q

what is a seidal test?

A

to assess the depth of injuries to the eye for example thorns (will create a river if aqueous humour is coming out)

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21
Q

what is rose bengal stain used for?

A

assess tear film quality
assess margins of conjunctival/corneal neoplaisia
fungal ulcers

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22
Q

what is the main issue seen with tear quality?

A

poor quality/quantity of mucoid layer so tear doesn’t stick to the eye

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23
Q

what is the best tool to sample the eye for cytology?

A

cytology brush (cervical smear swabs)

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24
Q

why should atropine not be used to dilate the pupil for eye examination?

A

last too long - remain dilated for 6 weeks

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25
Q

what is tonometry used for?

A

measure pressure in the eye

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26
Q

is upper or lower eyelid laceration better for the horse?

A

lower (better prognosis) - spreads less of the tear film

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27
Q

how much debridement do eyelid lacerations need?

A

minimal - very good blood supply

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28
Q

is a medial or lateral eyelid laceration better for the horse?

A

lateral (better prognosis) - tear ducts found medially

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29
Q

why are sarcoids around the eye problematic?

A

difficult to surgically remove due to eyelid
creams can be damaging to eye of they get in

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30
Q

what is the most common neoplasia seen on the third eyelid?

A

squamous cell carcinomas

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31
Q

how are masses on an eyelid removed?

A

cut out mass and continue excision downwards to then pull skin below it up to make a new eyelid

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32
Q

what are the layers of the cornea?

A

epithelium
stroma
descemet membrane
endothelium

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33
Q

what are the clinical signs of ulcerative keratitis?

A

pain
blepharospasm
epiphora
photophobia

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34
Q

why is ulcerative keratitis common in horses?

A

eyes in prominent position on side of head (stick out)

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35
Q

what is a superficial ulcer?

A

just epithelium damaged but stroma is intact

36
Q

what is done to treat superficial ulcers?

A

topical antimicrobial to prevent secondary infection
(heal well with no complications/scars)

37
Q

what is a deeper ulcer?

A

epithelium damaged and some of the stroma

38
Q

what is done to treat a deeper ulcer?

A

topical antimicrobials
(heal well but tend to scar)

39
Q

what is keratomalacia also known as?

A

melting ulcer

40
Q

what causes a melting ulcer?

A

activation/production of proteolytic enzymes by corneal epithelial cells, leucocytes or microbial organisms

41
Q

what therapy can be used for keratomalacia (melting ulcers)?

A

topical serum
topical EDTA
topical acetylcysteine
topical tetracycline
systemic NSAIDs

42
Q

what its a descemetocele ulcer?

A

epithelium and stroma destroyed down to the descemet membrane

43
Q

why is a descemetocele ulcer such an emergency?

A

eye at risk of burst - very thin layer holding it together

44
Q

how are descemetocele ulcers treated medically?

A

aggressive use of the following…
topical serum
topical EDTA
topical acetylcysteine
topical tetracycline
systemic NSAIDs

45
Q

how can descemetocele ulcer be treated surgically?

A

conjunctival flap

46
Q

if there is a full thickness corneal laceration what can happen?

A

iris prolapse (plugs hole)
eye empties

47
Q

what is the prognosis for full thickness corneal laceration?

A

good if treated before secondary infection occurs

48
Q

how can stroll abscesses be treated?

A

medical - antimicrobial therapy
surgical - deride and corneal graft

49
Q

how are superficial stroll abscesses treated?

A

debride epithelium and drain

50
Q

what causes viral keratitis?

A

equine herpes virus 2

51
Q

what is used to treat viral keratitis?

A

topical idoxuridine
topical trifluorothymidine
topical aciclovir (this is best)

52
Q

should corticosteroids be used for viral keratitis?

A

try treat without it as it makes recurrences more likely

53
Q

how common is fungal keratitis seen in the UK?

A

rare (common in US)

54
Q

how fast do fungal keratitis cases resolve?

A

very slowly

55
Q

how is fungal keratitis treated?

A

takes weeks of therapy (enucleation quicker)
antifungals (get worse before better) - voriconazole

56
Q

how would the onset of immune mediated keratopathies be described?

A

insidious

57
Q

how are immune mediated keratopathies treated medically?

A

topical corticosteriods
cyclosporine A
doxycycline

58
Q

what is uveitis?

A

inflammation of uvea (iris, ciliary body, choroid)

59
Q

what makes up the uvea of the eye?

A

iris
ciliary body
choroid

60
Q

how can uveitis be categorised?

A

posterior or anterior
acute or equine recurrent uveitis (ERU)

61
Q

what are the three forms of equine recurrent uveitis?

A

active
quiescent (dormant)
insidious (wax/wane)

62
Q

what is a major component of uveitis?

A

it is immune mediated

63
Q

what are 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

64
Q

what are the clinical signs of posterior uveitis?

A

variable pain (often mild)
vitritis
retinal changes
(subtle)

65
Q

how is uveitis treated if there is no ulcer present?

A

topical corticosteroids
topical atropine

66
Q

how is uveitis treated if there is an ulcer present?

A

topical NSAIDs
topical atropine

67
Q

how long is uveitis treated for?

A

treat until normal and then for a further 6 weeks

68
Q

what are some surgical treatment options for uveitis?

A

suprachoroidal cyclosporine implant
pars plana vitrectomy
enucleation

69
Q

what are some possible long term complications of uveitis?

A

atrophy granula iridica
synechiae
cataracts
glaucoma
retinal pathology
blindness
phthisis bulbi

70
Q

what is synechiae?

A

iris sticks to things (usually the lens)

71
Q

what is a cataract?

A

any opacity of the lens

72
Q

how are cataracts diagnosed?

A

retroillumination (opacities appear dark)
direct focal illumination (transillumination) - cataracts appear white

73
Q

what are the types of cataracts in horses?

A

capsular
nuclear
perinuclear (cortical)
equatorial
sutural
complete

74
Q

how can cataracts be treated medically?

A

they can’t be - can treat underlying condition if there is one

75
Q

what age can catarac surgery be performed?

A

ideally very young - before 4 months old (complications in adult)

76
Q

what surgery is carried out to treat cataracts?

A

phacoemulsification

77
Q

why is glaucoma uncommon in horses?

A

high pain threshold
not looked for in horses
two drainage options for aqueous humour

78
Q

what are the clinical signs of glaucoma?

A

hydrophthalmos/buphthalmos (increase in size)
corneal oedema
corneal striae (membrane tears)
lens luxation
blindness

79
Q

what colour does a oedematous cornea present as?

A

blue

80
Q

how can glaucoma be treated medically?

A

carbonic anhydrase inhibitor
beta blockers - timolol
NSAIDs/corticosteroids

81
Q

what carbonic anhydrase inhibitor is used for glaucoma?

A

dorzolamide (topical)

82
Q

what are some surgical treatment options for glaucoma?

A

laser destruction of ciliary bodies
aqueous shunts
enucleation

83
Q

how good is the blood supply to the fundus of horses?

A

paurangiotic (poor) - absent at 6 o’clock

84
Q

what shape is the optic nerve on the fundus?

A

oval (round in foals)

85
Q

what colour is the optic nerve on the fundus?

A

salmon-pink

86
Q

what are the sections of the tapetal fundus?

A

neurosensory retina
retinal pigmented epithelium
tapetum
choroid
sclera

Equine (fourth year) (11 decks)

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