9, 10 - posterior segment Flashcards Preview

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

Flashcards in 9, 10 - posterior segment Deck (132):
1

what tunic is the outer layer of the eye?

fibrous tunic

2

what makes up the fibrous tunic?

cornea
sclera

3

what tunic is the middle tunic?

vascular tuinc

4

what makes up the vascular tunic?

choriod, ciliary body, iris / uvea

5

what is the inner layer of the eye?

neural tunic

6

what makes up the neural tunic?

neural retina and retinal pigmented epithelium

7

what are the 2 humors of the eye?

where is each loc?

- aqueous humor: occupies the anterior chamber

- vitreous humor: occupies the posterior cavity / segment

8

the retina has ___ distinct layers

10

9

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

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

10

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

optic N
tapetum lucidum

11

where is the tapetum lucidum loc in most animals?

what animals are exceptions?

dorsal fundus

exceptions: camelids
primates
swine
squirrels
birds
some marsupials

12

how does the tapetum lucidum differ in carnivores vs ungulates?

cellular in carnivores
fibrous in ungulates

13

what shape is the tapetum lucidum?

triangular

14

t/f

fundoscopy is the examination of the retina

false

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

15

what structure is the posterior component of the fibrous tunic?

the sclera

16

what is the deepest layer of the fundus?

- the outermost layer of the globe
- furthest layer from the viewer

the sclera

17

what color is the sclera?

white or pale pink

18

what is the lamina cribrosa?

where is it loc?

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

19

what is the choriod?

posterior component of the uvea or vascular tunic

vascualar structure

20

describe the blood vessels of the choroid?

radially-oriented w minimal branching

appear pink-to-orange

21

that is the tapetum?

what structure is the tapetum part of ?

a mirror like reflective layer

a component of the choroid

22

what molecule is a part of the tapetum in dogs?

cats?

dogs - zinc cysteine
cats - riboflavin

23

what shape and location is the tapetum?

often triangular
loc in dorsal fundus

24

t/f

the tapetum is present in all animals

false

25

what are the components of the retina?

- retinal pigmented epithelium (RPE)
- neural retinal
- retinal vasculature

26

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

pigmented: over non-tapetal region [variable]

non-pigmented: over the tapetum

27

where is the neural retina loc?

appearance?

lies over the retinal pigmented epithelium

it is transparent [unless detached]

28

describe the retinal vasculature.

how does it differ btwn dogs and cats?

branching, dark blood vessels

dogs: anastomose in a ring on the optic disc

cats: end/begin at the edge of the optic disc

29

what Diagnositcs are done for posterior segment examination?

- visual testing
- ophthalmoscopy
- electrodiagnostics
- other / ancillary

30

what diagnostics are important for visual / behavioral testing?

menace response
tracking behavior
maze test

31

how is tracking behavior tested?

see if patient's eyes follow a dropped cotton ball

32

what are 2 types of maze tests?

why is each important?

scotopic - done in dim light

photopic - done in ambient light

*helps to distinguish rod and cone dysfunction

33

t/f

the menace response is present in all animals

false

NOT in very young animals b/c learned response

34

what animals are considered precocial? altricial?

significance?

precocial: develop later => puppy/kitten around 4 weeks

altricial: develop early => foal around 2 wks and lamb/goat about 8-14 days

35

what is the pathway of the menace response?

afferent: optic N -> thalamus (lateral geniculate nucleus) -> visual cortex in occipital lobe -> perception in frontal cortex


efferent: frontal cortex -> cerebellum -> facial N -> blink response

36

what does the dazzle reflex test?

- sub cortical reflex

- tests a good portion of visual pathways

37

what does the pupillary light reflex (PLR) test?

is it present in retinal dysfunction?

- reflex through the mid brain

- may be present w significant retinal dysfunction

38

is the dazzle reflex cortical or sub cortical?

sub cortical

39

what is the pathway of the pupillary light reflex?

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

40

what do you need for a good fundus exam?

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

mydriasis!!! to see entire fundus

41

what drugs can be used to cause mydriasis ?

what are the important properties of each?

atropine - long acting and slow onset

tropicamide - short acting and fast onset

42

describe direct ophthalmoscopy.

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

43

what do different settings on the ophthalmoscope mean?

setting depends on location of lesion in the eye

44

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

0 D
+8D
+12D
+20D

0 = fundus
8 = posterior lens
12 = anterior lens
20 = cornea lens

45

describe view with indirect ophthalmoscopy?

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

46

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

higher magnification

47

what does electroretinograpy measure?

retinal photoreceptor function

rods and cones

48

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

"seagull sign"

49

what does ocular u/s allow visualization of?

- the retina when lens or cornea is opaque

- the orbital portion of the optic nerve

50

what does CT or MRI reveal?

orbital portion of the optic nerve

51

describe a normal canine fundus?

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

can look yellow / yellow

52

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

atapetal - lack pigment - can see retinal vessels

dark red optic nerve head

orange/red choroidal vessels loc behind the retina

53

what does the tapetum of the puppy look like

blue before 4 months old b/c immature

54

what does cat fundus look like?

round

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

55

domestic animals are better adapted for nocturnal or day vision?

nocturnal

56

what Hertz of flickering light are animals adapted to see?

70-80 Hertz

57

why is night vision improved in animals?

large pupil
tepetum lucidum is reflective
more rod photoreceptors

58

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

dim

cones

59

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

b/c they have fewer cone receptors

60

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

rostro laterally

binocular

61

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

laterally

monocular

62

what type of color blind are horses compared to humans?

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

orange and light blue color blind

horses have 2 cones - blue and red/green

can see yellow and blue hues
NO intermediate colors

63

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?

cones

blue and yellow-green cones

red/green color blind

64

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

dogs: 20/70

cats: 20/100

65

what does a horse fundus look like?

parangiotic -> few retinal vessels, therefore more opaque

66

what does a bovine fundus look like?

darker optic nerve head

dorsal retinal vessels tend to intertwine like twizzlers

vessels are present on the fundus

67

what does a rabbit fundus look like?

marangiotic fundus - vessels and nerves follow a horizontal line

68

what is uniique about an avian fundus?

black structure present - the pectin

*fxns as a nutrient source for optic nerve head

69

how can the reflectivity of the fundus be altered?

hyper reflective

hypo reflective

70

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

absent tapetum

retinal thinning d/t degeneration

71

how does hypo reflectivitty occur in the fundus?

increased retinal thickness

cells or fluid

72

what pathology occurs in the vessels of the fundus?

3 conditions

- vascular attenuation
- vascular tortuosity
- hemorrhage

73

what is vascular attenuation?

fewer vessels and smaller vessels

74

what is vascular tortuosity?

vessels become more engorged / coiled than normal

75

t/f

retinal hemorrhage is usually a 1* condition

false

usually is a 2* condition

76

what are some common causes of retinal hemorrhage?

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

77

what is retinal detachment?

neurosensory retina separation from the underlying retinal pigmented epithelium

78

what are signs of retinal detachment?

sub retinal fluid accumulation

retinal tears [rhegmatogenous]

79

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

serous
exudative
hemorrhagic

80

where does the retina attach to the optic nerve?

at the periphery

81

what are some rule outs associated with retinal detachment?

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

82

under what circumstances might retinal detachment occur spontaneously?

if the 1* cause is addressed

83

what is the prognosis of retinal detachment?

guarded for vision

70% with Sx

84

how is retinal detachment treated?

correct 1* cause
Sx

85

what breeds are predisposed to developmental retinal dysplasia?

cocker spaniel
english springer spaniel
labrador

86

what etiologies may lead to retinal dysplasia?

intra uterine infections [viral]
toxicoses
radiation
nutrition

87

abnormal retinal folding may occur as a result of what?

retinal dysplasia

88

what is the etiology of collie eye anomaly?

inherited
developmental

89

what are the pathognomonic lesions for collie eye anomaly?

- choroidal hypoplasia
- posterior segment coloboma
- retinal detachment

90

what is PRA or PRD?

etiology?

progressive retinal atrophy or degeneration

inherited

91

what occurs during PRA/D?

photoreceptor degeneration

92

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

ERG

93

which photoreceptors are affected in PRA/D?

what type of blindness?

rods then cones - night blindness occurs first

eventually total blindness

94

PRA/D leads to what 2* condition?

cataracts

95

what is SARD?

etiology?

sudden acquired retinal degeneration - photo receptors sudden degeneration

unknown etiology

96

typical signalment of SARD?

middle aged FM dog MC

97

what systemic abnormalities occur with SARD?

- resemble cushings dz
- PU/PD, weight gain, polyphagie
- elevated ALT, ALP

98

what is etiology and common presentation of feline retinal degeneration?

often occurs 2* to what condition?

idiopathic cause

inherited: abyssinian and persian breeds

2* to retinal detachment / retachment

99

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

enrofloxacin

100

what does taurine deficiency cause in the eye?

in the heart?

irreversible retinal degeneration

reversible dilated cardiomyopathy

101

what is chorioretinitis?

what is the origin?

inflammation of the retina and choriod

origin is choroid

102

what 2 types of chorioretinits are there?

active dz
inactive dz

103

what is seen in active chorioretinitis?

hypo reflective
pigmentation variable
INDISTINCT margins to lesions
hemorrhage
raised

104

what is seen in inactive dz?

hyper reflective
pigmentation

WELL DEFINED margins

105

what are causes of canine chorioretinitis?

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

106

what are causes of feline chorioretinitis?

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

107

tx of chorioretinitis?

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

108

neoplasia of the fundus:
common?
prognosis?
Tx?

uncommon
1* or 2*
guarded to poor prognosis

Tx: enucleation, laser

109

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

- micropapilla
- optic N hypoplasia

110

2 developmental dzz of optic N:

small optic disc

optic N coloboma

111

what is optic N coloboma?

hole in optic disc

112

what are 3 acquired dzz of the optic N?

papilledema
optic neuritis
glaucoma

113

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

micropapilla

114

which dz of the optic N is animal usually blind?

optic N hypoplasia

115

what does papilledema look like?

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

116

etiology of papilledema?

neoplasia
hydrocephalus
head trauma

117

what is optic neuritis?

inflammation of optic N

118

is animal blind or visual in case of optic neuritis?

blind

119

presentation of optic neuritis?

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

bilateral blindness w dilated pupils

120

etiologies of optic neuritis?

intra cranial causes
see ddx for chorioretinitis

121

Tx of optic neuritis?

supportive care
anti inflammatories
immunosuppression - but risky if infectious etiology

122

diagnostics for optic neuritis?

comparable thorough work up as with uveitis

CT scan
CSF tap
good referrel

123

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

ganglion cell destruction - loss of optic N axons

124

what is appearance of optic N in glaucoma?

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

125

prognosis of glaucoma from optic N pathology?

poor for return of vision once ganglion cell loss occurs

126

what are 2 dzz of the vitreous?

persistent hyaloid

vitreous degeneration

127

what is etiology of persistent hyaloid?

PHPV / PHTVL

developmental - persistant tunica vasculosis

128

what are 2 causes of vitreous degeneration?

asteroid hyalosis
synersis

129

what is synersis of vitreous?

liquefaction

130

what is asteroid hyalosis?

calcium phospholipid deposits in the vitreous

131

what pathology of the eye looks like a snow globe?

the particulates in the eye move opposite the head motion

vitreous degeneration

132

how might an orbital mass affect the posterior segment?

orbital mass may push eye out and cause elevation