Globe and Orbit Flashcards
a part of the adnexa, the conical boney structure that contains the eyeball and periorbital cone
Boney orbit
What does the boney orbit contain
1) Eyeball
2) Periorbital cone
supportive cone like structure that contains the eyeball, extraocular muscles, fat, vessels, and fascia that reside within the orbit
Periorbital cone
Where is the periorbital cone
within the orbit
structure that contains the eyeball, extraocular muscles, fat, vessels, and fascia
ligamentous structure that forms the lateral boundary of the boney orbit in cats and dogs
orbital ligament
abnormal protrusion of the eye from the orbit.
abnormal position but normal globe size
Exophthalmos
T/F: the globe is larger in exophthalmos, which is why it ptroudes
False- abnormal position but normal size
abnormal recession of the eye within the orbit
glboe is normal size
enophthalmos
abnormal enlargement of the eyeball
normal position
ex: only caused by glaucoma
Buphthalmos
congenitally small and malformed globe
micropthalmos
an acquired shrunken globe, most often from severe or chronic inflammation
Phthisis bulbi
anterior displacement of the globe such that the eyelids are caught behind the equator of the globe
Proptosis
deviation of one or both eyes, so that both eyes are not directed at the same object
strabismus
What is the purpose of the boney orbit
1) Bony fossa for protection
2) Provides foramen for vascular and neural access
3) Depth and position of orbit helps dictate visual field and depth perception
surgical procedure to remove all contents of periorbital cone
enucleation
what sinuses are close to the orbit
front and maxillary sinuses
orbital disease can cause sinus disease and vise versa
ex: sinusal diseases can impact the orbit
like tooth root abscess
dental disease often induces
orbital or periorbital disease
especially the carnassial tooth (4th maxillary premolar)
What tooth commonly induces orbital or periorbital disease
especially the carnassial tooth (4th maxillary premolar)
what salivary gland is close to the orbit where inflammation of this tissue will lead to displacement of the globe
Zygomatic salivary gland
What muscles are often associated/involved with orbital inflammation **
1) Masseter
2) Temporalis
3) Pterygoid
swelling or atrophy can influence the eye
How does the mandible influence orbital disease *
movement of the ramus of mandible compresses inflammed orbital soft tissues and can cause severe pain
What might be preventing a dog from eating
orbital disease - open the mouth and see if there is pain, this may be causing them not to eat
T/F: dogs have complete orbit
false- incomplete orbit
T/F: felines have complete orbit
false - incomplete orbit
T/F: horses have a complete orbit
true- for protection (head butting)
what is the advantage of incomplete orbit
allows greater movement of the ramus of the mandible for biting
what forms the lateral boundary of the orbital rim
orbital ligament
Do dogs or cats have a shorter orbital ligament
cats- gives their boney more protection relative to the dog
In brachycephalics, the orbital ligament ________
spans a greater portion of the orbital rim
What differences to the orbit do brachycephalics have
1) Orbital ligament spans a greater portion of the orbital rim in brachycephalic dogs
2) Orbit is much shallower, relative to dolichocephalic dogs
these structures make them susceptible to ocular disease
visual field is determined by
the position of the orbit within the skill
this is influences by your environmental niche and feeding habits
are brachycephalic or dolichocephalic dogs more susceptible to ocular disease
Brachycephalic breeds
1) Orbital ligament spans a greater portion of the orbital rim in brachycephalic dogs
2) Orbit is much shallower, relative to dolichocephalic dogs
Disorders of globe position
1) Exopthalmos
2) Strabismus
3) Enopthalmos
Disorders of globe size
1) Bupththalmos
2) Phthisis bulbi
3) Microphthalmos
What are the clinical signs of exophthalmos *
1) Third eye lid protrusion (pushing on it) **
2) facial swelling
3) Soft palate bulging
4) Pain opening mouth/anorexia
5) fever
What typically causes exophthalmos in older dogs
likely orbital neoplasia-
-often malignant
-slowly progressive
-often non-painful
What typically causes exophthalmos in younger dogs*
orbital cellulitis/abscess
-working dogs and stick chewers
-Acute onset
-often painful
What are the clinical signs of retrobulbar neoplasia
1) Exophthalmos (gradual onset)
2) Elevated 3rd eyelid
3) No pain on opening mouth
4) Globe deviation (strabismus) -> position may indicate location of mass
strabismus due to retrobulbar abscess is typically
dorso-lateral strabismus
where do retrobulbar masses typically occur
ventral and medial to the globe this pushes the eye out and lateral (dorsolateral strabismus)
What are common causes of exophthalmos
1) Orbital neoplasia (older dogs)- malignant, slowly progressive, often non-painful
2) Orbital cellulitis/asbcess (younger dogs)- acute onset and very painful
3) Masticatory muscle myositis
4) Extraocular myositis
5) Zygomatic salivary gland mucocele
6) Retrobulbar hemorrhage
Which is painful, which is non-painful
-Orbital neoplasia
-Orbital cellulitis/abcess
Orbital neoplasia: non-painful
Orbital cellulitis/abscess: painful
Exophthalmos is protrusion of the globe and often the _________ *
third eyelid
Masses in the orbital space will
change position of the glboe depending on the location
An older dog with exophthalmos and lateral strabismus likely has _______ *
A retrobulbar mass ventral and medial to the globe that pushes the eye out and laterally
How does masticatory muscle myositis cause exophthalmos
reduction of the orbital space causes the globe to be pushes out from the orbit
results in inflammatory extraocular myositis = bilateral googly eyes
then when atrophy set in, this will cause enopthalmos
Masticatory muscle myositis causing exophthalmos typically unilateral or bilateral
bilateral
What are the clinical signs of Orbital cellulitis/abscess
-Rapid onset
-Elevated 3rd eyelid
-exopthalmos
-conjunctivities
-pain on opening mouth (cats)
typically younger dogs
What typically causes periorbital inflammation / infection
-Retrobulbar abscess
-Salivary mucoceles
-immune mediated myositis
-tooth rooth abscess
-orbital cellulitis
-sinusitis
dx: CT/MRI or ultrasound
How do you diagnose periorbital inflammation / infection
-ultrasound is best way (also CT or MRI)
-retrobulbar aspiration
What breeds will have normal exophthalmos due to their short orbits
brachycephalic breeds
Conformational Exophthalmos
exophthalmos that is “ normal” in brachycephalics due to their shallow orbits and straight face
bilateral
no protrusion of nictitans
typically have lateral strabismus
leads them more susceptible to disease
buphthalmos
enlarged globe typically due to glaucoma
third eyelid is not protruding with the buphthalmic globe in general
What is a major clinical sign for an eye that looks enlarged that confirms it is Buphthalmos and not exophthalmos *****
Buphthalmos generally does not have protrusion of the third eye lid
also Buphthalmos will have increased intraocular pressure
How do you tell Buphthalmos from Exopthalmos **
1) Increased intraocular pressure
2) No protrusion of the third eyelid
3) Look from above at corneal curvature to see if there is anterior displacement of a normal sized globe (exophthalmos)
4) Look from straight ahead (horse)
5) Retropulse globe -push eye into orbit through closed eyelid - exopthalmic globe will have limited retropulsion compared to normal eye
Painful if retrobulbar abscess or inflammation
How does retropulsing the glboe differ in dogs with exopthalmos vs buphthalmos *
Exopthalmos: will not have limited retropulsion compared to the normal eye
Buphthalmos: feels firmer
Might be happening if a dog has exopthalmos and their is pain upon retropulsion of the globe **
retrobulbar abscess or inflammation
How do you diagnose exophthalmos *
1) Look from above or straight on- compare to normal eye
2) Retropulse globe- push eye into orbit through closed eyelid
3) Nictitans protrusion: generally present with true exophthalmos
Diagnostic approach for exophthalmos
-Complete general and ophthalmic examination - observe for orbital globe symmetry and pain on opening mouth
-CBC/ CHEM
+/- chest rads for tumor metastasis for neoplasia
advanced imaging (CT/MRI)
Tissue sampling (fine needle aspiration-less specific and biopsy)
If you see peri-orbital swelling how do you get a sample for further diagnostics
aspirate behind the molars
differentials:
tooth root abscess
zygomatic mucocele
cellulitis
foreign body
trauma
What are the two treatment approaches to orbital neoplasia *
1) Globe sparing - most often palliative
-Radiation
-Surgical exploration
-Chemotherapy
2) Glove removal (also palliative)
Enucleation: removal of the eye
Exenteration: removal of the eye and all orbital contents
What are three consequences of being exophthalmic
1) dry eye
2) corneal ulceration
3) retinal detachement
removal of the globe and secretory components: eyelids, lacrimal glands, and 3rd eye lid
enucleation
removal of the globe and all orbital contents (secretory components, periorbital fat, muscles)
exenteration
what is enucleation, what else is removed, aside from the globe
secretory components: eyelids, lacrimal glands, 3rd eyelids
What are the 2 treatment approaches for orbital cellulitis/abscess *
1) Medical (if eating)
NSAID or Steroids AND broadspectrum antbitoics (ie Clavamox)
2) Surgical exploration and/or drainage
What are the 3 causes on enopthalmos
1) Orbital volume imbalances: ex: atrophy of muscles
2) Active globe retractions (skeletal muscle- retractor bulbi CN VI) -could be due to corneal pain
3) Passive globe retraction (smooth muscles of periorbital cone- sympathetic- Horners)
What are main causes of orbital volume imbalances leading to enophthalmos
1) Dehydration
2) Emaciation or cachexia
3) Myopathies
What might cause enophthalmos due to active globe retraction (Retractor bulbi)
ocular pain (ie corneal pain)
What might cause enopthalmos due to passive retraction (periorbital cone muscles)
Horner’s syndrome- smooth muscles of periorbital cone is under sympathetic innervation
enophthalmos from ocular pain is likely due to
corneal ulcers
What are the clinical signs of corneal ulcers
1) Enophthalmos (retraction of the globe from pain)
2) Blepharospasm (Closing of eyelids)
3) Raised 3rd eyelid
4) Miosis -> reflex uveitis
Why do you see miosis with corneal ulceration
from reflex uveitis
a condition where the pupil of the eye is constricted or abnormally small
miosis
the dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response
mydriasis
What happens if the muscles of mastication are atrophied (ie. masticatory muscle myositis- inflammation or steroid use)
orbital volume imbalances -> causes enophthalmos
What medication can lead to loss of surrounding musculature and enophthalmos
chronic steroid use
“pred head”
What are possible complications of enophthalmos
1) Increased space for third eyelid
2) Third eyelids covers globe- vision impairment
3) Entropion - from lack of globes supporting
What are common clinical signs of enophthalmos due to loss of musculature
1) facial muscular loss (unilateral or bilateral)
2) third eyelid protrusion
3) entropion
What are the 4 clinical signs of Horner’s syndrome **
1) Ptosis
2) Enophthalmos
3) Third eyelid elevation 4) Miosis
Ptosis
a condition that causes the upper eyelid to droop or fall, which can affect one or both eyes
sympathetic denervation to the eye and ocular adnexa leads to
Horner’s Syndrome
1) Ptosis- dropping of upper eyelid
2) Enophthalmos - sunken back eye
3) Third eyelid elevation 4) Miosis- constricted
How do you distinguish Horner’s from a painful eye?
Proparacaine - numbs the eye. if its reflex to corneal ulcer then it will resolve within 90 seconds
Horners: 1 drop of sympathomimetic (Phenylephrine) and then the 3rd eyelid will come up and eye will dilate
With Horner’s Syndrome, upon dropping phenyelphrine in the eye, will you see results sooner in pre or post-ganglionic lesions?
Post-ganglionic lesions you will see retraction of 3rd eyelid and dilation sooner <20minutes
40-60 minutes: Preganglionic lesion
With pre-ganglionic lesions of Horner’s Disease you will see
Retraction of third eye lid and dilation of the eye within
40-60 minutes
way longer than post ganglionic lesions
With post-ganglionic lesions of Horner’s Disease you will see retraction of the 3rd eyelid and dilation of the eye within
<20minutes
way shorter than pre-ganglionic lesions
In Horner’s Disease, dropping phenylephrine will result in
1) Dilation of the eye (mydriasis)
2) Retraction of third eyelid
Post-ganglionic lesion: <20min
Pre-ganglionic lesions: 40-60min
a congenitally small and malformed globe
microphthalmos
an acquired shrunken globe, most often from severe or chronic inflammation and causes lack of aqueous humor production
leading to decrease in size of the globe
often not visual
Phthisis bulbi
What are the 2 disorders that lead to a smaller globe size
1) Microphthalmos- congenital and malformed
2) Phtisis bulbi- acquired shrinkage due to chornic inflammation and lack or aqueous humor production
deviation of one or both eyes so that both eyes are not directed at same object
strabismis
What are causes of congenital stabismus
1) Normal variation- brachycephalic dogs with divergent stabismus due to abnormal volume
2) Siamese cats- convergent strabismus (abnormal visual processing)
3) Hydrocephalus- ventrolateral divergent strabismus (abnormal orbital volume)
What breed typically gets convergent strabismus
Siamese cats
leads to abnormal visual processing
What kind of strabismus does hydrocephalus lead to
Ventrolateral divergent strabismus
due to abnormal orbital volume
Siamese cats get _________ strabismus while Brachycephalic dogs get _______ strabismus
Siamese: convergent strabismus
Brachycephalics: divergent strabismus
Brachycephalic breeds have a “normal variation” that leads to _________ strabismus from ___________
divergent strabismus from abnormal orbital volume
What are acquired causes of strabismus
1) Mechanical or nervous dysfunction of any rectus muscle
CN III: dorsal, ventral, medial rectus muscles and ventral oblique
CN IV: Dorsal oblique
CN VI: Retractor bulbi and lateral lectus
2) Imbalances of orbital volume -> third eyelid neoplasia
What strabismus would you see from dysfunction of CN VI
Medial strabismus
CN VI works to innervate retractor bulbi and lateral rectus so dysfunction would cause the eye to move medially
What strabismus would you see from medial rectus damage follow proptosis
Lateral strabismus
Why is acquired lateral strabismus the most common
1) Masses tend to grow ventromedial which causes a dorsolateral strabismus
2) Medial rectus is the shortest muscles which damage to it commonly causes a lateral strabismus
anterior displacement of the globe such that the eyelids are caught behind the equator of the globe *
Proptosis
Proptosis is very common in
brachycephalic breeds
-often involves minimal trauma
At what distinction do you consider an anterior displaced eye “Proptosis” *
if the globe is pushes such that the eyelids are caught behind the equator of the globe
-Proptosis would want to fix
What are two considerations when considering proptosis prognosis *
1) Vision?
Poor prognosis as >75% are blinded (optic nerve trauma)
2) Globe retention?- variable prognosis
indicators:
-Rupture of eye
-Hyphema
-Orbital bone fractures
-Owner compliance
In dogs with proptosis, what is the prognosis of gaining vision
75% are blinded (optic nerve trauma)
Dogs have ______ extraocular muscles torn with proptosis have better prognosis of globe retentions
<3 extraocular muscles torn
With proptosis, what tells you there is a better prognosis of globe retention
1) Brachycephalics
2) <3 extra-ocular muscles torn
3) Positive direct and consensual PLRs
With proptosis, what tell you there is a poor prognosis
1) Cats
2) Dolichocephalic dogs
3) >3 extraocular muscles torn
4) Ruptured eye
5) Hyphema
6) Orbital fractures
How do you treat proptosis
1) E-collar and lubricate eye
2) Pain management, sedation, or anesthesia- vagal response can cause cardiac arrest/death
3) Clip and clean eyelids
4) Place stay sturues
5) Apply counter pressure to the eye with a clean, flat, blunt surface
6) Place temporary partial tarsoorhaphy - at the meibomian glands
7) Insititute appropiate medical therapy
8) Do not remove tarsohaphy until orbital swelling is completely resolves (at least 2-3 weeks)
a surgical procedure in which the eyelids are closed
can be temporary or permanent, partial or complete
Tarsorrhaphy
What should you do for proptosis after-care
-Ecollar- hard plastic
-Topical antibiotic
-+/- topical atropine- if uveitis or ulceration is present
-oral antibiotic
-oral NSAID or steroid
-additional analgesia
-manage complication if arise
What are complications of Proptosis tx
1) Corneal ulceration - from misplaced sutures
2) Loosening sutures
3) Strabimus- medial rectus is shortest and most easily torn leading to lateral strabismus
4) Keratoconjunctivitis sicca
5) Blindness
6) Repeated proptosis
7) Need for enucleation
What is the shortest rectus muscle and most prone to being torn
Medial rectus
-commonly to get lateral strabismus from this
you should never apply contact solution to the eye
True
what is the purpose of the mucin components of tear film
bind serous layer to the cornea
