Final Exam - Orbital Disease Flashcards
what is the bony orbit?
part of the adnexa, conical bony structure that contains the eyeball & periorbital cone
what is buphthalmos?
literally means cows eye - refers to the abnormal enlargment of the eyeball
T/F: in buphthalmos, the size of the eyeball is abnormal, but the position is normal
TRUE
for our purpose, what is the one cause of buphthalmos for companion animals?
glaucoma
what is enophthalmos?
abnormal recession of the eye within the orbit
what is exophthalmos?
abnormal protrusion of the eye from the orbit with abnormal positioning & a normal globe size
what is horner’s syndrome?
sympathetic denervation to the eye & ocular adnexa with 4 classic clinical signs
what are the 4 classic signs of horner’s syndrome?
enophthalmos, ptosis, miosis, & protrusion of the 3rd eyelid
what is microphthalmos?
congenitally small & malformed globe
what is the oribital ligament?
ligamentous structure that forms the lateral boundary of the bony orbit in dogs & cats
what is the perioribital cone?
supportive cone-like structure that contains the eyeball, extraocular muscles, fat, vessels, nerves, & fascia that resides WITHIN THE ORBIT
what is phthisis bulbi?
acquired shrunken globe that is most often from severe or chronic inflammation
what is proptosis?
anterior displacement of the globe such that the eyelids are caught BEHIND THE EQUATOR OF THE GLOBE!!!
what is strabismus?
deviation of one or both eyes so that both eyes are not directed at the same object
T/F: the eyeball = eye = globe = all tissue within & including the cornea/sclera
TRUE
what is this anatomic structure?
periorbital cone
what sinuses are you worried about for a dog or cat with orbital disease?
frontal & maxillary sinuses - orbital disease can cause sinus disease & vice versa
why are you concerned about dental health in an animal with orbital disease?
dental disease often induces orbital or periorbital disease - especially the carnassial tooth (4th maxillary premolar)
how can the zygomatic salivary gland induce orbital disease?
inflammation of this tissue will lead to displacement of the globe
what muscles of mastication are involved with orbital inflammation?
masseter, temporalis, & pterygoid
how is the ramus of the mandible implicated in orbital disease?
movement compresses inflamed orbital soft tissues & can cause severe pain
why should you avoid using a mouth gag in cats?
risk of blindness! compresses carotid/maxillary arterial supply to the orbit
what is an alternative option that can be used instead of a mouth gag for a cat?
needle cap!
the optic canal houses what nerve?
CN II
the orbital fissure contains what nerves?
CN III, IV, V (ophthalmic), & VI
what are the significant foramina & fissures that may be affected in an animal with orbital disease?
- infraorbital foramen 2. optic canal 3. orbital fissure 4. rostral & caudal alar foramina 5. external acoustic meatus
between dogs & cats, which has a shorter orbital ligament? why?
both dogs & cats have an open orbit that is completed on the lateral boundary of the orbital rim by the orbital ligament - much shorter in cats given their orbit has more bony protection when compared to dogs
how is the orbit & orbital ligament different in brachycephalic dogs? why is this important?
relative to skull size, the orbital ligament spans a greater portion of the orbital rim & the orbit is much shallower - brachycephalic animals will be more susceptible to ocular disease!!!
what animals have a closed orbit? why os this important?
ruminants & horses - complete bony coverage at the orbital rim, so they have more protection from trauma relative to dogs & cats
what is your most sensitive assessment for enophthalmos/exophthalmos?
dorsal view assessment!!!
what is the purpose of retropulsion?
identifies mass effect within the orbital space
what are your tests for examining orbital symmetry?
orbital palpation - for fractures, masses, pain dorsal view assessment - looking for enophthalmos & exophthalmos & retropulsion - looking for mass effect within the orbital space
what are the 4 main disorders of globe position?
- exophthalmos 2. enophthalmos 3. strabismus 4. proptosis
what are the 3 main disorders of globe size?
- buphthalmos 2. phthisis bulbi 3. microphthalmos
what are the common clinical signs associated with exophthalmos?
3rd eyelid protrusion, facial swelling, soft palate bulging, pain when opening the mouth, & fever
what is the most common mechanism of exophthalmos?
orbital volume imbalance
what are some examples of causes of exophthalmos?
orbital neoplasia, orbital cellulitis/abscess, zygomatic salivary gland, mucocele, masticatory muscle myositis, extraocular myositis, & retrobulbar hemorrage
what are the 2 most common conditions causing exophthalmos in dogs? what clinical signs are associated with each?
orbital neoplasia - often malignant, slowly progressive, & often non-painful & orbital cellulitis/abscess - seen in working dogs/stick chewers, acute onset, & often painful
why do brachycephalic dogs have a normal exophthalmos?
they have it because of their shalow orbits
how can lateral deviation of the globe present in orbital disease?
tumor involving the 3rd eyelid
T/F: masses in the orbital space will change the position of the globe depending on their location
TRUE
why are dogs with orbital cellulitis/abscesses so painful upon opening their mouth?
the soft tissues around the eye/masticatory muscles become inflamed, so movement of the ramus of the mandible becomes painful!!
what are your 2 treatment options for exophthalmos due to orbital neoplasia?
glaobe sparing (palliative) - radiation, surgical exploration, & chemotherapy & globe removal (also palliative) - enucleation (removal of the eye) or exenteration (removal of the eye & all orbital contents)
what are your 2 treatment options for exophthalmos due to orbital cellulitis/abscesses?
medical - anti-inflammatories (NSAID or steroids) & abx (broad spectrum) & surgical exploration and/or drainage
why should you be careful when performing an enucleation in a cat?
optic chiasm can be affected by direct tension of the eye during enucleation can blind the normal eye!!!
why should you be careful if establishing drainage for a dog with orbital cellulitis/abscess?
there are many vascular & nervous structures in this area & there is poor exposure
what common clinical signs are seen in animals with enophthalmos?
facial muscle loss (uilateral or bilateral), 3rd eyelid protrusion, & entropion
what are the 3 common mechanisms for enophthalmos?
- orbital volume imbalances 2. active globe retraction - skeletal muscle (retractor bulbi - CN VI) 3. passive globe retraction - involves smooth muscles of the periorbital cone, involving sympathetic system
what are some common causes of enophthalmos due to orbital volume imbalances?
dehydration, emaciation/cachexia, myopathies, & space occupying lesions anterior to the globe
how does ocular pain cause enophthalmos?
active retraction - active muscle tone!!!
how does horner’s syndrome cause enophthalmos?
passive retraction due to loss of muscle tone!!!
why does the 3rd eyelid protrude in an animal with horner’s syndrome?
loss of sympathetic tone!!!! passive protraction occurs
what 2 conditions do you need to be careful to not confuse with enophthalmos?
don’t confuse with microphthalmia & phthisis bulbi - both are disorders of globe size
what are congenital causes of strabismus?
- normal variation - brachycephalic dogs due to an abnormal orbital volume 2. siamese cats - convergent strabismus & abnormal visual processing 3. hydrocephalus - ventrolateral divergent strabismus due to abnormal orbital volume
how does mechanical or nervous dysfunction cause acquired strabismus?
CN III - dorsal, ventral, medial rectus muscles, & ventral oblique (can cause a few different types of strabismus) CN IV - dorsal oblique & CN VI - retractor bulbi - can also be caused by imbalance of orbital volume
T/F: in proptosis in brachycephalic dogs, minimial trauma is seen
TRUE
what two things affect prognosis in an animal with a proptosed eye?
vision & globe retention
how does vision affect prognosis of proptosed eyes?
> 75% are blinded due to optic nerve trauma - poor prognosis
what factors of globe retention indicate a negative prognosis for a proptosed eye?
rupture of the eye, hyphema, orbital bone fracture, & poor owner compliance
what is tarsorrhapy?
surgical procedure in which the eyelids are closed
when is the tarsorrhapy removed for a proptosed eye?
only when orbital swelling has completely resolved (at least 2-3 weeks)
how is a proptosed eye treated?
e-collar is placed & the eye is lubricated, proper pain management. sedation, & anesthesia is given with careful monitoring (vagal response can cause cardiac arrest or death) - place stay sutures & apply counter pressire to the eye with a clean, flat, blunt surface & then place a temporary partial tarsorrhapy at the meibomian glands & institute appropriate medical therapy
what is the after care indicated for a proptosed eye?
e-collar!!!!! topical abx, topical atropine if uveitis/ulceration is present, oral abx, oral anti-inflammatories, & additional analgesia (tramadol)
what type of strabismus is commonly seen as a complication after an eye has proptosed?
lateral strabismus - medial rectus muscle is the shortest & most easily torn muscle!
why do we see corneal ulceration as a common complication following a proptosed eye correction?
corneal ulceration mostly from misplaced sutires
what are some complications seen with proptosed eyes?
corneal ulceration, loosening of sutures, strabismus, KCS, blindness, repeated proptosis, & need for enucleation
