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IP 11 Ophthalmology > 1: the orbit - pearce > Flashcards

1: the orbit - pearce Flashcards

1
Q

when referring to location w/in the eye, what is the appropriate way to say dorsal?
ventral?
lateral?
medial?

A 
dorsal = superior
ventral = inferior
lateral = temporal
medial = nasal
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2
Q

how many tunics are in the eye?

A

3

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3
Q

what are the 3 tunics of the eye?

A

fibrous tunic
vascular tunic
neural tunic

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4
Q

what makes up the fibrous tunic?

A

cornea

sclera

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5
Q

what makes up the vascular tunic?

A

uveal tract => iris, ciliary body, choroid

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6
Q

what is the function of the zonules in the eye?

A

to attach the ciliary body to the lens

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7
Q

what and where is the choriod?

A

vascular layer loc behind the retina

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8
Q

what is the iris?

A

color portion of eye

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9
Q

what makes up the neural tunic?

A

retina

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10
Q

what is the retina? what does it look like?

A

thin and microscopic visibility

neural tissue - the most advanced and complex structure in the eye

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11
Q

what makes up the internal optical media?

A

aqueous humor
lens
vitreous humor

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12
Q

where is the aqueous humor loc? what does it contain?

A

loc in the front chamber of the eye, the anterior chamber - anterior to the iris

has aqueous humor

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13
Q

where is the posterior chamber loc? what does it contain?

A

loc btwn iris and lens

has aqueous humor

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14
Q

what is the posterior segment? what does it contain?

A

contains vitreous humor

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15
Q

what is primary goal of ophthalmology in terms of patient care? and if this is not achievable, what is the next goal?

A

vision

comfort

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16
Q

what are main components of ophthalmology?

A
  • signalment
  • hx: chronology, medications
  • neurophthalmic exam
  • MDB
  • ophthalmic exam
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17
Q

what do you need to conduct an ophthalmic exam?

A
  • bright, focal light source
  • darn environment
  • magnification
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18
Q

what are 2 methods to conduct a retinal exam?

A
  • indirect ophthalmoscopy

- direct ophthalmoscope

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19
Q

how to assess vision in an animal?

A
  • vision-directed behavior
  • tracking
  • menace response
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20
Q

def the orbit:

A

a conical cavity containing the eye and its supporting structures

includes bony orbit and soft tissue

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21
Q

what are the 2 type of bony orbits?

A

“closed” or “complete”

“open” or “incomplete”

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22
Q

which animals have an open orbit? closed orbit?

why?

A

herbivores have closed orbit - orbit completely encased in bone so the mobility of the mandible is limited - jaw cannot open as much

carnivores have open orbit - part of the orbit is not encased in bone - allows much greater mobility of the mandible so the jaw can be opened wider

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23
Q

what is the orbital lig?

A

present in carnivores, over the area of the orbit that is not encased in bone, to provide some protection to the orbit in that area, while still allowing a higher range of motion for the jaw

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24
Q

what is the orbital cone, what structures make it up and what structures define it?

A

essentially, it is the “stuff” around the eye

  • CT
  • extra ocular Mm
  • Nn
  • blood vessels
  • fat
  • smooth M
  • endorbita/periorbita

defined by the endorbita and extra ocular Mm

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25
Q

what is the endorbita/periorbita?

A
  • fibrous CT loc next to the bone of the orbital wall
  • encircles extra ocular Mm
  • boundra btwn intra-conal and extra-conal spaces
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26
Q

what is the function of the extra-ocular Mm?

A

to move the eye

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27
Q

what are the extra-ocular Mm and how does each move the eye?

A

superior oblique, inferior oblique - move eye rotationally
retractor bulbi - insertion M; retro pulses the eye / pulls the eye into socket
lateral, medial, ventral and dorsal rectus Mm - move eye side to side or up and down, respectively

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28
Q

what muscles are extra-conal?

A

temporalis M, pterygoid M, masseter M

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29
Q

what soft tissues are extra-conal?

A

muscles, blood vessels and Nn, fat and CT, glands, paranasal sinuses, nasal cavity, oral cavity, roots of teeth, Cr cavity / fossa

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30
Q

what glands are loc extra-conal?

A

lacrimal

zygomatic salivary

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31
Q

t/f

tooth root abscesses do not affect the eye.

why or why not?

A

false

tooth root abscesses can affect the eye - swelling in the oral cavity/gingiva can push out the globe and affect vision - it is loc near the eye and space is very small

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32
Q

what is exophthalmos?

A

globe loc too far rostral - is being pushed out of the orbit/socket

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33
Q

what is enophthalmos?

A

globe loc too far cd

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34
Q

what is proptosis?

A

equator of globe anterior to palpebral fissure

essentially, severe exopphthalmos where globe is coming out of the socket/orbit

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35
Q

what is the palpebral fissure?

A

the opening of the eyelids

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36
Q

what is the MDB for ophthalmology exam?

A

Schirmer tear test
Fluorescein stain
Tonometry

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37
Q

how to examine for orbital dz?

A
  • look from above
  • retropulsion
  • neurophthalmic exam
  • MDB
  • ophthalmic exam - anterior segment and fundus
  • oral exam
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38
Q

what is retropulsion? what is a normal retropulsion of the globe?

A

close patient eyes and push on eyeball - should be able to push it in a little bit

should NOT be resistance or pain - if there is, something is wrong

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39
Q

if the eye appears large and/or swollen, what are 2 differentials?

A

exophthalmos and bupthalmos

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40
Q

what is bupthalmos?

A

eye is too large

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41
Q

how to distinguish exophthalmos from bupthalmos?

A

look at alignment and diameter of cornea

exo: cornea is NOT aligned but has a normal diameter
bup: cornea is aligned but has a larger diameter than it should

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42
Q

what are c/s of orbital dz?

A
  • inc or dec scleral show
  • dec retropulsion
  • elevation of Nictitans
  • difficulty of discomfort opening mouth
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43
Q

why is the Nictaitans, or 3rd eyelid, important to evaluate in orbital dz?

A

functions as a sentinal for orbital dz

it should be down but will elevate in orbital dz

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44
Q

why might difficulty opening the mouth indicate orbital dz?

A

the motion of the ramus of the mandible will push on the orbit and cause pain or discomfort in the globe in some orbital dz processes

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45
Q

t/f

pain when opening the mouth is a positive prognostic indicator in terms of orbital dz

A

true

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46
Q

what are basic diagnostics carried out during orbital dz exam?

A 
PE - look for systemic inflammation or systemic metastatic dz
CBC, chem
skull x rays
fine needle aspirates
specialty procedures
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47
Q

what specialty procedures might be performed in an orbital dz exam?

A
  • orbital u/s
  • angiography
  • advanced imaging (CT/MRI)
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48
Q

what are 2 forms of enophthahlmos?

what is a good way to distinguish btwn the two forms?

A

congenital
acquired

get a good history

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49
Q

what is microphthalmos

A

globe that is too small - congenital or acquired

presents as enophthalmos

50
Q

what are 2 causes of congenital enophthalmos?

A
  • microphthalmos and anophthalmos
51
Q

what is anophthalmos?

how common is this condition?

A

a form of congenital enophthalmos in which there is no eye

VERY RARE

52
Q

what is microphthalmos?

when is it most common to occur?

A
  • congenitally small globe
  • multiple ocular defects common
  • merle or white coat/color diluted animals primarily [double dapple breeding of 2 merles]
53
Q

what is the prognosis of congenital enophthalmos?

A

vision: poor prognosis
comfort: fair to guarded

54
Q

what are 2 forms of acquired enophthalmos?

A
  • phthisis bulbi: acquired dec globe size

- normal globe size with loss of orbital tissue volume

55
Q

under what circumstances might phthisis bulbi occur?

A

end stage glaucoma, trauma, uveitis

56
Q

under what circumstances might loss of orbital tissue volume occur?

A

bilateral: dehydration, emaciation/weight loss
unilateral: muscle or tissue atrophy => myositis, surgery, radiation

57
Q

what is acquired enophthalmos?

A

a condition which causes the retraction of the globe into the orbit, when the animal was born normal

58
Q

what are some common concurrent conditions typically seen with exophthalmos?

A
  • lagophthalmos: inability to completely open / close eyelids
  • strabismus: deviation of visual axis
59
Q

what are some c/s assoc w exophthalmos?

A
  • conjunctival hyperemia or chemosis
  • nictitans elevation
  • pain upon retropulsion or opening mouth
  • keratitis
60
Q

if an exophthalmic dog is not painful when opening the mouth, what is a differential?

A

tumor

61
Q

what is the cause of exophthalmos?

A

space occupation

mass effect [inside or outside of cone] pushing the globe in one direction or another

62
Q

what might cause space occupation, leading the exophthalmos?

what is more common?

A

cells: hyperplasia, inflammatory, neoplasia
fluid: blood, serum/cystic, lipid

air

MC cells - fluid is more of a ‘zebra’

63
Q

possible etiologies of exophthalmos inflammatory dzz?

A
  • orbital abscess
  • orbital cellulitis
  • myositis: masticatory, extra ocular
64
Q

c/s of orbital cellulitis or abscess?

A
  • unilateral usually
  • Nictitans elevation
  • pain opening mouth
  • fever
  • inappetance
  • inflammatory leukogram
65
Q

possible etiologies of cellulitis / abscess?

A

tooth abscess
sinus infection
hematogenous spread
penetrating injury

66
Q

what Dx is necessary to distinguish btwn cellulitis and abscess?

if the client does not want do to this exam, what can be done next?

A

orbital u/s

  • alternative: can give pain control and abx - cellulitis will improve w abx but abscess will not [abscess needs to be drained surgically]
  • this is less desirable b/c patient is very painful so waiting it out means more discomfort for animal
67
Q

what is the difference btwn cellulitis and abscess?

A

cellulitis: solid cells
abscess: pocket of puss

68
Q

therapy for cellulitis /abscess?

A

systemic abx
drainage if abscess
soft food
corneal lubrication

69
Q

what is presentation of acute masticatory muscle myositis?

A
  • facial muscle inflammation
  • bilateral exophthalmos
  • nictitans elevation
  • pain on jaw movement
  • pyrexia
70
Q

what muscles are inflamed in case of masticatory muscle myositis?

A

pterygoid
temporalis
masseter

71
Q

are masticatory mm intra or extra conal? what is result when they are inflammed?

A

they are extra conal

they push the globe out when they are inflamed

72
Q

what is presentation of chronic masticatory muscle myositis?

A

enophthalmos

atrophy / fibrosis of muscles

73
Q

what test is diagnostic for masticatory muscle myositis?

A

2M aby serum test: positive is diagnostic

74
Q

what changes might be observed on CBC/chem panel for masticatory muscle myositis?

A
  • peripheral eosinophilia maybe

- elevated CK

75
Q

masticatory muscle myositis treatment - acute and chronic cases?

A

acute: systemic immunosuppression until CK is normal and jaw is moveable
chronic: conservative management of eophthalmos

supportive care maybe b/c hard to eat when painful jaw

76
Q

what is the presentation of extra ocular muscle myositis?

A

bilateral exophthalmos, bug eyed appearance with lots of scleral show

“deer in headlights” or stressed look

fixed gaze

No nictitans protrusion

77
Q

is extra ocular M myositis painful?

A

NO

78
Q

what dog breed is extra ocular muscle myositis common in?

A

golden retreivers

79
Q

what is etiology if extra ocular muscle myotisit?

A

auto immune myositis

80
Q

where are extra ocular muscles located?

A

within the cone

81
Q

dx extra ocular muscle myositis?

A

clin presentation is big b/c very distinct appearance

options but not necessary usually:
imaging
biopsy

82
Q

tx extra ocular muscle myositis?

A

immunosuppression

83
Q

prognosis of extra ocular muscle myositis?

A

recurrences common

secondary problems if chronic cases, but NOT common: cases: enophthalmos, strabismus / fibrosis

84
Q

what is the origin of primary orbital neoplasia?

secondary?

A

primary: the orbit
secondary: metastasis TO the orbit from elsewhere in body

85
Q

t/f

orbital neoplasia is usually benign

A

false

usually malignant, 80-90% malignacy rate

86
Q

what is the typical presentation for orbital neoplasia?

A
  • gradual onset
  • exophthalmos
  • nictitans elevation
  • lack of retropulsion
  • absence of pain opening mouth
87
Q

dx of orbital neoplasia?

A
  • CBC, chem, U/a
  • ocular u/s
  • CT/MRI
  • cytology: mass and associated lnn
  • abdominal and thoracic x rays: metastasis check
  • biopsy: CT or u/s guided or Sx
88
Q

therapy for orbital neoplasia?

A

dep on tumor type:

sx
chemo
radiation

89
Q

what is prognosis of orbital neoplasia?

A

guarded to poor

80-95% malignancy

90
Q

what is traumatic proptosis?

A

the equator of the globe lies anterior to the palpebral fissure, due to pressure from trauma

can be slightly proptosed to extremely proptosed

91
Q

common causes of traumatic proptosis?

A
  • bite wounds: BDLD attach
  • blunt trauma: HBC, kicked by horse
  • heavy restraint in some brachycephalic dogs [iatrogenic]
92
Q

in what type of dog is traumatic proptosis MC?

A

brachycephalic: the more brachycephalic a dog is, the less pressure that is required to cause this condition

RARE in cats and mesencephalic / dolicocephalic dogs

93
Q

in case of proptosis, what is the first thing you should do?

A

stay calm

94
Q

what can you tell the owner to do immediately to help their pet that has proptosis?

A

keep eye moist in transport - corn or olive oil, eye drops, KY jelly, artificial tears, etc

95
Q

dx proptosis?

A
  • thorough PE - do NOT miss pneumothorax or something severe and anesthetize dog
  • neuro exam
  • ophthalmic exam: orbital fractures, direct/consensual PLR, ocular motility, fluorescein stain, intra ocular exam
96
Q

postitive prognostic indicators of proptosis

A
  • pos consensual PLR

- voluntary movement of the globe [some extra ocular M attachment remains]

97
Q

t/f

pupil size is a reliable indicator of positive prognosis of proptosis

A

false - pupil size is NOT a reliable indicator

a miotic pupil indicates intact
parasympathetic innervation

98
Q

what are negative prognostic indicators of a proptosis?

A
  • transected nerve
  • chronic proptosis (over 48 hrs)
  • hyphema
  • corneo-sclera laceration
  • rupture > 3 extra ocular muscles
  • dolicocephalic or cat
  • complete bony orbit
99
Q

what muscles often tear during proptosis?

what might occur as a result?

A

medial

strabismus

100
Q

t/f

if a proptosed globe of a cat is able to be put back in, the cat will likely have normal vision

A

false - cat will definitely not have normal vision return

101
Q

what might cause hyphema when a proptosis has occurred?

A

scleral rupture

severe uveal trauma

102
Q

what is the tx for proptosis?

A
  • Sx: replace (pos prognostic indicators) or enucleate (negative prognostic indicators)

stabilize patient, keep cornea lubricated

103
Q

t/f
if there are positive prognostic indicators to suggest a surgical replacement of the globe might resolve the proptosis successfully, it is a good idea to try it anyways - if it fails, you can always remove the globe later

A

true

104
Q

during Sx replacement of proptosis what kinds of sutures are used?

when placing them, what orientation do you want the eyelids to fall into?

A

horizontal matterss sutures

want to exit at the lid margins so the lid margins DO NOT evert

pull the lid over the globe rather than pushing the globe down

105
Q

what is the highest “ott” suture that should be used in optical surgery?

A

4-0

106
Q

medical tx for proptosis?

A
  • systemic abx
  • systemic anti inflammatory: NSAID and steroid
  • topical triple abx: ointment, QID
  • e collar
  • tarsorrhaphy 2-3 weeks
  • lots of lubrication
107
Q

what complications might arise during a proptosis replacement?

A
  • lagophthalmmos
  • KCS
  • strabismus [very common b/c hard to reattach Mm]
  • blindness
  • phthisus bulbi -> uveitis
108
Q

what is lagophthalmos?

A

inability to blink

109
Q

what types of enucleation are there?

A
  • subconjunctival

- transpalpebral

110
Q

how does subconjunctival enucleation work?

benefit to this method?

A
  • remove “through” the conjunctiva
  • remember to remove the Nictitans and residual conjunctiva
  • cleaner sample for histopath
111
Q

how does transpalpebral enucleation work?

when should this be used over subconjunctival enucleation?

A
  • remove “through” the eyelids
  • infected eyes
  • intraocular neoplasia
112
Q

what is enucleation?

A

removal of the globe

113
Q

what is exenteration?

A

removal of the entire orbital contents, muscle and contents - down to the bone

114
Q

what is evisceration?

A

removal of the intra ocular contents - leaving the fibrous tunic [cornea and sclera] behind

115
Q

what kind of block is used to perform enucleation?

A

retro bulbar block - local anesthetic

116
Q

t/f

it is always necessary to ligate the optic N in animals

A

false - humans but not animals

117
Q

t/f

the best method to remove the globe during enucleation is to twist and pull the globe straight out of the orbit

A

false

remove in physiologic manner - rotate the globe - but DO NOT twist and pull - you can avulse the optic chiasm and cause blindness in the other eye

118
Q

although the risk exists in both species, is it more likely to cause contralateral blindness in an enucleation procedure in a dog or a cat? why?

A

cats - bc they have a very short distance btwn the globe and chiasm

119
Q

what is an advantage of the retro bulbar block to perform enucleation?

A

it reduces hemorrhage b/c less epinephrine is present, due to the lidocaine
also, dec amt general anesthesia needed

120
Q

t/f

there is a high risk of an animal bleeding out from the blood vessles in its eye if they are not properly ligated during enucleation procedures.

A

false

this is the case in humans but not in animals - just cut it

IP 11 Ophthalmology (13 decks)

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