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IP 11 Ophthalmology > 9, 10 - posterior segment > Flashcards

9, 10 - posterior segment Flashcards

1
Q

what tunic is the outer layer of the eye?

A

fibrous tunic

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2
Q

what makes up the fibrous tunic?

A

cornea

sclera

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3
Q

what tunic is the middle tunic?

A

vascular tuinc

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4
Q

what makes up the vascular tunic?

A

choriod, ciliary body, iris / uvea

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5
Q

what is the inner layer of the eye?

A

neural tunic

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6
Q

what makes up the neural tunic?

A

neural retina and retinal pigmented epithelium

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7
Q

what are the 2 humors of the eye?

where is each loc?

A
  • aqueous humor: occupies the anterior chamber

- vitreous humor: occupies the posterior cavity / segment

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8
Q

the retina has ___ distinct layers

A

10

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9
Q

what is the basic pathway of signal transmission through the retina?

A

light hits the retinal pigmented epithelial cells -> signal sent to photoreceptors -> signal sent to bipolar cells -> synapse on ganglion cells -> go to optic N head and into brain

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10
Q

the posterior portion of the globe has 2 very specialized regions. what are they?

A

optic N

tapetum lucidum

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11
Q

where is the tapetum lucidum loc in most animals?

what animals are exceptions?

A

dorsal fundus

exceptions: camelids
primates
swine 
squirrels
birds
some marsupials
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12
Q

how does the tapetum lucidum differ in carnivores vs ungulates?

A

cellular in carnivores

fibrous in ungulates

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13
Q

what shape is the tapetum lucidum?

A

triangular

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14
Q

t/f

fundoscopy is the examination of the retina

A

false

fundoscopy is a composite of the posterior segment structures: the retina, choriod (and tapetum lucidum +/-) and sclera

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15
Q

what structure is the posterior component of the fibrous tunic?

A

the sclera

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16
Q

what is the deepest layer of the fundus?

  • the outermost layer of the globe
  • furthest layer from the viewer
A

the sclera

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17
Q

what color is the sclera?

A

white or pale pink

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18
Q

what is the lamina cribrosa?

where is it loc?

A

area considered to be the seed - allows the optic N fibers to go thru the globe and out into the orbit

loc in the sclera

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19
Q

what is the choriod?

A

posterior component of the uvea or vascular tunic

vascualar structure

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20
Q

describe the blood vessels of the choroid?

A

radially-oriented w minimal branching

appear pink-to-orange

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21
Q

that is the tapetum?

what structure is the tapetum part of ?

A

a mirror like reflective layer

a component of the choroid

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22
Q

what molecule is a part of the tapetum in dogs?

cats?

A

dogs - zinc cysteine

cats - riboflavin

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23
Q

what shape and location is the tapetum?

A

often triangular

loc in dorsal fundus

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24
Q

t/f

the tapetum is present in all animals

A

false

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25
Q

what are the components of the retina?

A
  • retinal pigmented epithelium (RPE)
  • neural retinal
  • retinal vasculature
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26
Q

what are the 2 regions of the retinal pigmented epithelium and where are they loc?

A

pigmented: over non-tapetal region [variable]

non-pigmented: over the tapetum

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27
Q

where is the neural retina loc?

appearance?

A

lies over the retinal pigmented epithelium

it is transparent [unless detached]

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28
Q

describe the retinal vasculature.

how does it differ btwn dogs and cats?

A

branching, dark blood vessels

dogs: anastomose in a ring on the optic disc
cats: end/begin at the edge of the optic disc

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29
Q

what Diagnositcs are done for posterior segment examination?

A
  • visual testing
  • ophthalmoscopy
  • electrodiagnostics
  • other / ancillary
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30
Q

what diagnostics are important for visual / behavioral testing?

A

menace response
tracking behavior
maze test

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31
Q

how is tracking behavior tested?

A

see if patient’s eyes follow a dropped cotton ball

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32
Q

what are 2 types of maze tests?

why is each important?

A

scotopic - done in dim light

photopic - done in ambient light

*helps to distinguish rod and cone dysfunction

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33
Q

t/f

the menace response is present in all animals

A

false

NOT in very young animals b/c learned response

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34
Q

what animals are considered precocial? altricial?

significance?

A

precocial: develop later => puppy/kitten around 4 weeks
altricial: develop early => foal around 2 wks and lamb/goat about 8-14 days

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35
Q

what is the pathway of the menace response?

A

afferent: optic N -> thalamus (lateral geniculate nucleus) -> visual cortex in occipital lobe -> perception in frontal cortex
efferent: frontal cortex -> cerebellum -> facial N -> blink response

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36
Q

what does the dazzle reflex test?

A
  • sub cortical reflex

- tests a good portion of visual pathways

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37
Q

what does the pupillary light reflex (PLR) test?

is it present in retinal dysfunction?

A
  • reflex through the mid brain

- may be present w significant retinal dysfunction

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38
Q

is the dazzle reflex cortical or sub cortical?

A

sub cortical

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39
Q

what is the pathway of the pupillary light reflex?

A

optic N -> optic chiasm -> synapse bilaterally on neurons loc in pre tectal nuc -> axons synapse on parasympathetic nuclei of ocular motor N -> most cross over and synapse on the contra lateral ciliary para sympathetic nerves / ganglia

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40
Q

what do you need for a good fundus exam?

A

bright focal light source
patient at eye level
dark room
magnification (lens)

mydriasis!!! to see entire fundus

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41
Q

what drugs can be used to cause mydriasis ?

what are the important properties of each?

A

atropine - long acting and slow onset

tropicamide - short acting and fast onset

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42
Q

describe direct ophthalmoscopy.

A 
upright image
high magnification
easy to use
equipment readily available
shorter working distance
narrow field of view
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43
Q

what do different settings on the ophthalmoscope mean?

A

setting depends on location of lesion in the eye

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44
Q

what do the following settings on the direct ophthalmoscoope allow viewing of?

0 D
+8D
+12D
+20D

A 
0 = fundus
8 = posterior lens
12 = anterior lens
20 = cornea lens
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45
Q

describe view with indirect ophthalmoscopy?

A 
inverted image [upside down and backwards] 
wider field of view
stereopsis
requires practice to master
low magnification than direct
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46
Q

for indirect ophthalmoscopy, a lower number magnification means _____ (higher/lower) magnification?

A

higher magnification

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47
Q

what does electroretinograpy measure?

A

retinal photoreceptor function

rods and cones

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48
Q

what is the classic sign seen with ocular u/s to indicate retinal detachment?

A

“seagull sign”

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49
Q

what does ocular u/s allow visualization of?

A
  • the retina when lens or cornea is opaque

- the orbital portion of the optic nerve

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50
Q

what does CT or MRI reveal?

A

orbital portion of the optic nerve

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51
Q

describe a normal canine fundus?

A

triangluar in shape, vessels anastomose over the optic N head, myelination of optic N head

can look yellow / yellow

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52
Q

what does a normal canine fundus look like if the dog is blue eyed?

A

atapetal - lack pigment - can see retinal vessels

dark red optic nerve head

orange/red choroidal vessels loc behind the retina

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53
Q

what does the tapetum of the puppy look like

A

blue before 4 months old b/c immature

54
Q

what does cat fundus look like?

A

round

vessels stop at end of optic nerve; do NOT anastomose over the optic N head

55
Q

domestic animals are better adapted for nocturnal or day vision?

A

nocturnal

56
Q

what Hertz of flickering light are animals adapted to see?

A

70-80 Hertz

57
Q

why is night vision improved in animals?

A

large pupil
tepetum lucidum is reflective
more rod photoreceptors

58
Q

rods detect light in ____ conditions and _____ detect light in bright conditions

A

dim

cones

59
Q

animals can see some colors but they are more muted than colors humans can see. why?

A

b/c they have fewer cone receptors

60
Q

carnivores have good predatory vision b/c their eyes are set more _______ in the head so they have enhanced _____ vision

A

rostro laterally

binocular

61
Q

the eyes of prey animals are set more ______ on the head, giving them better ______ vision or panoramic views

A

laterally

monocular

62
Q

what type of color blind are horses compared to humans?

how many cones to horses have?
what hues can they see?

A

orange and light blue color blind

horses have 2 cones - blue and red/green

can see yellow and blue hues
NO intermediate colors

63
Q

dogs are dichromat because they have fewer _____

these structures allow them to see which colors?

as a result, what type of color blind are they when compared to human vision?

A

cones

blue and yellow-green cones

red/green color blind

64
Q

what is the approximate visual acuity of dogs and cats compared to humans?

A

dogs: 20/70
cats: 20/100

65
Q

what does a horse fundus look like?

A

parangiotic -> few retinal vessels, therefore more opaque

66
Q

what does a bovine fundus look like?

A

darker optic nerve head

dorsal retinal vessels tend to intertwine like twizzlers

vessels are present on the fundus

67
Q

what does a rabbit fundus look like?

A

marangiotic fundus - vessels and nerves follow a horizontal line

68
Q

what is uniique about an avian fundus?

A

black structure present - the pectin

*fxns as a nutrient source for optic nerve head

69
Q

how can the reflectivity of the fundus be altered?

A

hyper reflective

hypo reflective

70
Q

what are 2 circumstances under which hyper reflectivity occurs in the fundus?

A

absent tapetum

retinal thinning d/t degeneration

71
Q

how does hypo reflectivitty occur in the fundus?

A

increased retinal thickness

cells or fluid

72
Q

what pathology occurs in the vessels of the fundus?

3 conditions

A
  • vascular attenuation
  • vascular tortuosity
  • hemorrhage
73
Q

what is vascular attenuation?

A

fewer vessels and smaller vessels

74
Q

what is vascular tortuosity?

A

vessels become more engorged / coiled than normal

75
Q

t/f

retinal hemorrhage is usually a 1* condition

A

false

usually is a 2* condition

76
Q

what are some common causes of retinal hemorrhage?

A 
hypertension
hyper viscosity
coagulopathy
chorioretinitis [tick borne]
diabetes
2* to trauma or sx
77
Q

what is retinal detachment?

A

neurosensory retina separation from the underlying retinal pigmented epithelium

78
Q

what are signs of retinal detachment?

A

sub retinal fluid accumulation

retinal tears [rhegmatogenous]

79
Q

what type of fluid may be present in sub retinal fluid accumulation?

A

serous
exudative
hemorrhagic

80
Q

where does the retina attach to the optic nerve?

A

at the periphery

81
Q

what are some rule outs associated with retinal detachment?

A 
hypertension
hyperviscosity
spontaneous/idiopathic
coagulopathy
vitreous dz
chorioretinitis
2* to trauma or sx
82
Q

under what circumstances might retinal detachment occur spontaneously?

A

if the 1* cause is addressed

83
Q

what is the prognosis of retinal detachment?

A

guarded for vision

70% with Sx

84
Q

how is retinal detachment treated?

A

correct 1* cause

Sx

85
Q

what breeds are predisposed to developmental retinal dysplasia?

A

cocker spaniel
english springer spaniel
labrador

86
Q

what etiologies may lead to retinal dysplasia?

A

intra uterine infections [viral]
toxicoses
radiation
nutrition

87
Q

abnormal retinal folding may occur as a result of what?

A

retinal dysplasia

88
Q

what is the etiology of collie eye anomaly?

A

inherited

developmental

89
Q

what are the pathognomonic lesions for collie eye anomaly?

A
  • choroidal hypoplasia
  • posterior segment coloboma
  • retinal detachment
90
Q

what is PRA or PRD?

etiology?

A

progressive retinal atrophy or degeneration

inherited

91
Q

what occurs during PRA/D?

A

photoreceptor degeneration

92
Q

what diagnostic test reveals abnormalities of PRA/D before vision changes occur?

A

ERG

93
Q

which photoreceptors are affected in PRA/D?

what type of blindness?

A

rods then cones - night blindness occurs first

eventually total blindness

94
Q

PRA/D leads to what 2* condition?

A

cataracts

95
Q

what is SARD?

etiology?

A

sudden acquired retinal degeneration - photo receptors sudden degeneration

unknown etiology

96
Q

typical signalment of SARD?

A

middle aged FM dog MC

97
Q

what systemic abnormalities occur with SARD?

A
  • resemble cushings dz
  • PU/PD, weight gain, polyphagie
  • elevated ALT, ALP
98
Q

what is etiology and common presentation of feline retinal degeneration?

often occurs 2* to what condition?

A

idiopathic cause

inherited: abyssinian and persian breeds

2* to retinal detachment / retachment

99
Q

feline retinal degeneration may occur d/t toxin of what drug?

A

enrofloxacin

100
Q

what does taurine deficiency cause in the eye?

in the heart?

A

irreversible retinal degeneration

reversible dilated cardiomyopathy

101
Q

what is chorioretinitis?

what is the origin?

A

inflammation of the retina and choriod

origin is choroid

102
Q

what 2 types of chorioretinits are there?

A

active dz

inactive dz

103
Q

what is seen in active chorioretinitis?

A 
hypo reflective
pigmentation variable
INDISTINCT margins to lesions 
hemorrhage
raised
104
Q

what is seen in inactive dz?

A

hyper reflective
pigmentation

WELL DEFINED margins

105
Q

what are causes of canine chorioretinitis?

A 
viral - distemper
rickettsial dz - RMSF, e. canis
deep mycotic dz
neoplasia
immune mediated 
protozoal - toxo, neospora
idiopathic
106
Q

what are causes of feline chorioretinitis?

A 
viral - FeLV, FIV, FIP
deep mycotic dz
neoplasia
immune mediated
hypertension
toxo
idiopathic
107
Q

tx of chorioretinitis?

A
  • address underlying cause
  • systemic corticosteroid - controversial
  • topical corticosteroid - IF ANTERIOR SEGMEND INFLAMMATION b/c do NOT reach the posterior segment
108
Q

neoplasia of the fundus:
common?
prognosis?
Tx?

A

uncommon
1* or 2*
guarded to poor prognosis

Tx: enucleation, laser

109
Q

2 developmental dzz of optic N that lead to small optic disk:

A
  • micropapilla

- optic N hypoplasia

110
Q

2 developmental dzz of optic N:

A

small optic disc

optic N coloboma

111
Q

what is optic N coloboma?

A

hole in optic disc

112
Q

what are 3 acquired dzz of the optic N?

A

papilledema
optic neuritis
glaucoma

113
Q

with which dz of the optic N can the animal remain visual?

A

micropapilla

114
Q

which dz of the optic N is animal usually blind?

A

optic N hypoplasia

115
Q

what does papilledema look like?

A
  • swelling of the optic N d/t inc intra cranial pressure
  • distinct margins on disc
  • raised vessels at edge
116
Q

etiology of papilledema?

A

neoplasia
hydrocephalus
head trauma

117
Q

what is optic neuritis?

A

inflammation of optic N

118
Q

is animal blind or visual in case of optic neuritis?

A

blind

119
Q

presentation of optic neuritis?

A

optic disc is raised
fuzzy, indistinct disc margins
hemorrhage on or around optic N head

bilateral blindness w dilated pupils

120
Q

etiologies of optic neuritis?

A

intra cranial causes

see ddx for chorioretinitis

121
Q

Tx of optic neuritis?

A

supportive care
anti inflammatories
immunosuppression - but risky if infectious etiology

122
Q

diagnostics for optic neuritis?

A

comparable thorough work up as with uveitis

CT scan
CSF tap
good referrel

123
Q

what is the pathology of the optic nerve that leads to glaucoma?

A

ganglion cell destruction - loss of optic N axons

124
Q

what is appearance of optic N in glaucoma?

A

optic N is “cupped” or depressed - optic N head more prominent b/c axons are lost

125
Q

prognosis of glaucoma from optic N pathology?

A

poor for return of vision once ganglion cell loss occurs

126
Q

what are 2 dzz of the vitreous?

A

persistent hyaloid

vitreous degeneration

127
Q

what is etiology of persistent hyaloid?

A

PHPV / PHTVL

developmental - persistant tunica vasculosis

128
Q

what are 2 causes of vitreous degeneration?

A

asteroid hyalosis

synersis

129
Q

what is synersis of vitreous?

A

liquefaction

130
Q

what is asteroid hyalosis?

A

calcium phospholipid deposits in the vitreous

131
Q

what pathology of the eye looks like a snow globe?

the particulates in the eye move opposite the head motion

A

vitreous degeneration

132
Q

how might an orbital mass affect the posterior segment?

A

orbital mass may push eye out and cause elevation

IP 11 Ophthalmology (13 decks)

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