1: the orbit - pearce Flashcards
when referring to location w/in the eye, what is the appropriate way to say dorsal?
ventral?
lateral?
medial?
dorsal = superior ventral = inferior lateral = temporal medial = nasal
how many tunics are in the eye?
3
what are the 3 tunics of the eye?
fibrous tunic
vascular tunic
neural tunic
what makes up the fibrous tunic?
cornea
sclera
what makes up the vascular tunic?
uveal tract => iris, ciliary body, choroid
what is the function of the zonules in the eye?
to attach the ciliary body to the lens
what and where is the choriod?
vascular layer loc behind the retina
what is the iris?
color portion of eye
what makes up the neural tunic?
retina
what is the retina? what does it look like?
thin and microscopic visibility
neural tissue - the most advanced and complex structure in the eye
what makes up the internal optical media?
aqueous humor
lens
vitreous humor
where is the aqueous humor loc? what does it contain?
loc in the front chamber of the eye, the anterior chamber - anterior to the iris
has aqueous humor
where is the posterior chamber loc? what does it contain?
loc btwn iris and lens
has aqueous humor
what is the posterior segment? what does it contain?
contains vitreous humor
what is primary goal of ophthalmology in terms of patient care? and if this is not achievable, what is the next goal?
vision
comfort
what are main components of ophthalmology?
- signalment
- hx: chronology, medications
- neurophthalmic exam
- MDB
- ophthalmic exam
what do you need to conduct an ophthalmic exam?
- bright, focal light source
- darn environment
- magnification
what are 2 methods to conduct a retinal exam?
- indirect ophthalmoscopy
- direct ophthalmoscope
how to assess vision in an animal?
- vision-directed behavior
- tracking
- menace response
def the orbit:
a conical cavity containing the eye and its supporting structures
includes bony orbit and soft tissue
what are the 2 type of bony orbits?
“closed” or “complete”
“open” or “incomplete”
which animals have an open orbit? closed orbit?
why?
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
what is the orbital lig?
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
what is the orbital cone, what structures make it up and what structures define it?
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
what is the endorbita/periorbita?
- fibrous CT loc next to the bone of the orbital wall
- encircles extra ocular Mm
- boundra btwn intra-conal and extra-conal spaces
what is the function of the extra-ocular Mm?
to move the eye
what are the extra-ocular Mm and how does each move the eye?
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
what muscles are extra-conal?
temporalis M, pterygoid M, masseter M
what soft tissues are extra-conal?
muscles, blood vessels and Nn, fat and CT, glands, paranasal sinuses, nasal cavity, oral cavity, roots of teeth, Cr cavity / fossa
what glands are loc extra-conal?
lacrimal
zygomatic salivary
t/f
tooth root abscesses do not affect the eye.
why or why not?
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
what is exophthalmos?
globe loc too far rostral - is being pushed out of the orbit/socket
what is enophthalmos?
globe loc too far cd
what is proptosis?
equator of globe anterior to palpebral fissure
essentially, severe exopphthalmos where globe is coming out of the socket/orbit
what is the palpebral fissure?
the opening of the eyelids
what is the MDB for ophthalmology exam?
Schirmer tear test
Fluorescein stain
Tonometry
how to examine for orbital dz?
- look from above
- retropulsion
- neurophthalmic exam
- MDB
- ophthalmic exam - anterior segment and fundus
- oral exam
what is retropulsion? what is a normal retropulsion of the globe?
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
if the eye appears large and/or swollen, what are 2 differentials?
exophthalmos and bupthalmos
what is bupthalmos?
eye is too large
how to distinguish exophthalmos from bupthalmos?
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
what are c/s of orbital dz?
- inc or dec scleral show
- dec retropulsion
- elevation of Nictitans
- difficulty of discomfort opening mouth
why is the Nictaitans, or 3rd eyelid, important to evaluate in orbital dz?
functions as a sentinal for orbital dz
it should be down but will elevate in orbital dz
why might difficulty opening the mouth indicate orbital dz?
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
t/f
pain when opening the mouth is a positive prognostic indicator in terms of orbital dz
true
what are basic diagnostics carried out during orbital dz exam?
PE - look for systemic inflammation or systemic metastatic dz CBC, chem skull x rays fine needle aspirates specialty procedures
what specialty procedures might be performed in an orbital dz exam?
- orbital u/s
- angiography
- advanced imaging (CT/MRI)
what are 2 forms of enophthahlmos?
what is a good way to distinguish btwn the two forms?
congenital
acquired
get a good history
what is microphthalmos
globe that is too small - congenital or acquired
presents as enophthalmos
what are 2 causes of congenital enophthalmos?
- microphthalmos and anophthalmos
what is anophthalmos?
how common is this condition?
a form of congenital enophthalmos in which there is no eye
VERY RARE
what is microphthalmos?
when is it most common to occur?
- congenitally small globe
- multiple ocular defects common
- merle or white coat/color diluted animals primarily [double dapple breeding of 2 merles]
what is the prognosis of congenital enophthalmos?
vision: poor prognosis
comfort: fair to guarded
what are 2 forms of acquired enophthalmos?
- phthisis bulbi: acquired dec globe size
- normal globe size with loss of orbital tissue volume
under what circumstances might phthisis bulbi occur?
end stage glaucoma, trauma, uveitis
under what circumstances might loss of orbital tissue volume occur?
bilateral: dehydration, emaciation/weight loss
unilateral: muscle or tissue atrophy => myositis, surgery, radiation
what is acquired enophthalmos?
a condition which causes the retraction of the globe into the orbit, when the animal was born normal
what are some common concurrent conditions typically seen with exophthalmos?
- lagophthalmos: inability to completely open / close eyelids
- strabismus: deviation of visual axis
what are some c/s assoc w exophthalmos?
- conjunctival hyperemia or chemosis
- nictitans elevation
- pain upon retropulsion or opening mouth
- keratitis
if an exophthalmic dog is not painful when opening the mouth, what is a differential?
tumor
what is the cause of exophthalmos?
space occupation
mass effect [inside or outside of cone] pushing the globe in one direction or another
what might cause space occupation, leading the exophthalmos?
what is more common?
cells: hyperplasia, inflammatory, neoplasia
fluid: blood, serum/cystic, lipid
air
MC cells - fluid is more of a ‘zebra’
possible etiologies of exophthalmos inflammatory dzz?
- orbital abscess
- orbital cellulitis
- myositis: masticatory, extra ocular
c/s of orbital cellulitis or abscess?
- unilateral usually
- Nictitans elevation
- pain opening mouth
- fever
- inappetance
- inflammatory leukogram
possible etiologies of cellulitis / abscess?
tooth abscess
sinus infection
hematogenous spread
penetrating injury
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?
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
what is the difference btwn cellulitis and abscess?
cellulitis: solid cells
abscess: pocket of puss
therapy for cellulitis /abscess?
systemic abx
drainage if abscess
soft food
corneal lubrication
what is presentation of acute masticatory muscle myositis?
- facial muscle inflammation
- bilateral exophthalmos
- nictitans elevation
- pain on jaw movement
- pyrexia
what muscles are inflamed in case of masticatory muscle myositis?
pterygoid
temporalis
masseter
are masticatory mm intra or extra conal? what is result when they are inflammed?
they are extra conal
they push the globe out when they are inflamed
what is presentation of chronic masticatory muscle myositis?
enophthalmos
atrophy / fibrosis of muscles
what test is diagnostic for masticatory muscle myositis?
2M aby serum test: positive is diagnostic
what changes might be observed on CBC/chem panel for masticatory muscle myositis?
- peripheral eosinophilia maybe
- elevated CK
masticatory muscle myositis treatment - acute and chronic cases?
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
what is the presentation of extra ocular muscle myositis?
bilateral exophthalmos, bug eyed appearance with lots of scleral show
“deer in headlights” or stressed look
fixed gaze
No nictitans protrusion
is extra ocular M myositis painful?
NO
what dog breed is extra ocular muscle myositis common in?
golden retreivers
what is etiology if extra ocular muscle myotisit?
auto immune myositis
where are extra ocular muscles located?
within the cone
dx extra ocular muscle myositis?
clin presentation is big b/c very distinct appearance
options but not necessary usually:
imaging
biopsy
tx extra ocular muscle myositis?
immunosuppression
prognosis of extra ocular muscle myositis?
recurrences common
secondary problems if chronic cases, but NOT common: cases: enophthalmos, strabismus / fibrosis
what is the origin of primary orbital neoplasia?
secondary?
primary: the orbit
secondary: metastasis TO the orbit from elsewhere in body
t/f
orbital neoplasia is usually benign
false
usually malignant, 80-90% malignacy rate
what is the typical presentation for orbital neoplasia?
- gradual onset
- exophthalmos
- nictitans elevation
- lack of retropulsion
- absence of pain opening mouth
dx of orbital neoplasia?
- 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
therapy for orbital neoplasia?
dep on tumor type:
sx
chemo
radiation
what is prognosis of orbital neoplasia?
guarded to poor
80-95% malignancy
what is traumatic proptosis?
the equator of the globe lies anterior to the palpebral fissure, due to pressure from trauma
can be slightly proptosed to extremely proptosed
common causes of traumatic proptosis?
- bite wounds: BDLD attach
- blunt trauma: HBC, kicked by horse
- heavy restraint in some brachycephalic dogs [iatrogenic]
in what type of dog is traumatic proptosis MC?
brachycephalic: the more brachycephalic a dog is, the less pressure that is required to cause this condition
RARE in cats and mesencephalic / dolicocephalic dogs
in case of proptosis, what is the first thing you should do?
stay calm
what can you tell the owner to do immediately to help their pet that has proptosis?
keep eye moist in transport - corn or olive oil, eye drops, KY jelly, artificial tears, etc
dx proptosis?
- 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
postitive prognostic indicators of proptosis
- pos consensual PLR
- voluntary movement of the globe [some extra ocular M attachment remains]
t/f
pupil size is a reliable indicator of positive prognosis of proptosis
false - pupil size is NOT a reliable indicator
a miotic pupil indicates intact
parasympathetic innervation
what are negative prognostic indicators of a proptosis?
- transected nerve
- chronic proptosis (over 48 hrs)
- hyphema
- corneo-sclera laceration
- rupture > 3 extra ocular muscles
- dolicocephalic or cat
- complete bony orbit
what muscles often tear during proptosis?
what might occur as a result?
medial
strabismus
t/f
if a proptosed globe of a cat is able to be put back in, the cat will likely have normal vision
false - cat will definitely not have normal vision return
what might cause hyphema when a proptosis has occurred?
scleral rupture
severe uveal trauma
what is the tx for proptosis?
- Sx: replace (pos prognostic indicators) or enucleate (negative prognostic indicators)
stabilize patient, keep cornea lubricated
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
true
during Sx replacement of proptosis what kinds of sutures are used?
when placing them, what orientation do you want the eyelids to fall into?
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
what is the highest “ott” suture that should be used in optical surgery?
4-0
medical tx for proptosis?
- systemic abx
- systemic anti inflammatory: NSAID and steroid
- topical triple abx: ointment, QID
- e collar
- tarsorrhaphy 2-3 weeks
- lots of lubrication
what complications might arise during a proptosis replacement?
- lagophthalmmos
- KCS
- strabismus [very common b/c hard to reattach Mm]
- blindness
- phthisus bulbi -> uveitis
what is lagophthalmos?
inability to blink
what types of enucleation are there?
- subconjunctival
- transpalpebral
how does subconjunctival enucleation work?
benefit to this method?
- remove “through” the conjunctiva
- remember to remove the Nictitans and residual conjunctiva
- cleaner sample for histopath
how does transpalpebral enucleation work?
when should this be used over subconjunctival enucleation?
- remove “through” the eyelids
- infected eyes
- intraocular neoplasia
what is enucleation?
removal of the globe
what is exenteration?
removal of the entire orbital contents, muscle and contents - down to the bone
what is evisceration?
removal of the intra ocular contents - leaving the fibrous tunic [cornea and sclera] behind
what kind of block is used to perform enucleation?
retro bulbar block - local anesthetic
t/f
it is always necessary to ligate the optic N in animals
false - humans but not animals
t/f
the best method to remove the globe during enucleation is to twist and pull the globe straight out of the orbit
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
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?
cats - bc they have a very short distance btwn the globe and chiasm
what is an advantage of the retro bulbar block to perform enucleation?
it reduces hemorrhage b/c less epinephrine is present, due to the lidocaine
also, dec amt general anesthesia needed
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.
false
this is the case in humans but not in animals - just cut it
