Unit 1 - Orbit Flashcards
What are the bones of the orbit?
Maxilla, lacrimal, palantine, frontal, sphenoid, and zygomatic
What are the foramen of the caudal orbit?
Ethmoidal foramen, optic canal, orbital fissure, and alar foramen (rostral)
What are the glands of the orbit?
Lacrimal gland and zygomatic salivary gland
What are the vessels of the orbit?
Maxillary artery, deep facial vein, facial vein, anastomolic branch to the ventral external ophthalmic vein, angular vein of the eye
What nerve is in the orbit?
Lacrimal nerve
What are the seven extra-ocular muscles?
4 rectus muscles - dorsal, ventral, lateral, and medial
2 oblique muscles - dorsal and ventral
1 retractor bulbi muscle
What are the majority of the extra-ocular muscles innervated by?
CN III (oculomotor)
What extra-ocular muscle is not innervated by the oculomotor nerve? What are they innervated by
Superior oblique (CN IV) Lateral rectus and retractor bulbi (CN VI)
What are the components of the orbital exam?
Visual inspection - symmetry, position of third eyelid, position and motility of globe Palpation of the orbital rim Retropulsion of globes Vision and PLR Nasal air flow and discharge Ability/extent of mouth opening Oral exam
What are some possible clinical signs associated with orbital disease?
Exophthalmos, enophthalmos, strabismus, elevated third eyelid, conjunctival hyperemia, lagophthalmos, exposure keratitis, pain on palpation f the periorbital area, and pain on opening mouth
What is exophthalmos?
Normal sized globe displaced rostrally within the orbit due to increased orbital volume
What can cause exophthalmos?
Neoplasia, abscess/cellulitis, hemorrhage, vascular anomaly, mucocele, cyst, myositis, etc.
What is buphthalmos?
Enlarged globe
Need to differentiate this from exophthalmos
What is proptosis?
Forward displacement with entrapment of the eyelid margins behind the equator of the globe
Need to differentiate this from exophthalmos
T/F - Exophthalmos is a ‘normal’ conformation for brachycephalics.
True - their orbits are just normally shallow
Need to differentiate this from exophthalmos
What is enophthalmos?
Normal sized globe displaced caudally within the orbit due to globe retraction, loss of sympathetic tone, decreased orbital volume, or pressure anterior to the equator of the globe
What can cause enophthalmos?
Pain, Horner’s syndrome, muscle wasting, loss of orbital fat, orbital fractures, dehydration, extraocular muscle fibrosis, and adnexal neoplasia
What is microphthalmos?
Congenitally small globe(s)
Need to differentiate this from enophthalmos
What is phthisis bulbi?
A shrunken eye occurring after severe inflammation due to cessation of aqueous production
Need to differentiate this from enophthalmos
What procedures can be done for orbital sampling?
FNA/cytology and/or biopsy and histopathology
What are the approaches to orbital sampling?
Transconjunctival adjacent to the globe
Through the skin posterior to the orbital ligament
Orally caudal to the last upper molar tooth
What is divergent strabismus also known as? In what species is it common in?
Exotropia mainly in brachycephalic dogs
What is convergent strabismus also called? In what species is it common in?
Esotropia
Inherited in cats (autosomal recessive) - primarily in siamese
What is orbital cellulitis?
inflammation of the orbital tissues
What is the signalment for orbital cellulitis/abscess?
Young animal, acute onset, ‘chews sticks’
Possibly inappetant or decreased playing/chewing
What are some possible clinical signs for orbital cellulitis/abscess?
Unilateral exophthalmos +/- lagophthalmos Elevated third eyelid Injected conjunctival vessels Resistant to retropulsion +/- painful Pain on periorbital palpation Yelps when mouth opened Febrile
Orbital abscesses must be confirmed before treatment, how would you do that?
ultrasound or MRI
How do you drain an orbital abscess if accessible?
Incise the oral mucosa caudal to the last upper molar with a # 15 blade
Insert closed hemostat, advance slowly, then open
Collect samples
Leave open to drain
Remove nidus if present
What is the medical therapy for orbital cellulitis/abscess?
Broad-spectrum systemic antibiotics for at least 4 weeks (Clavamox preferred)
Hot pack orbital area if tolerated
Single IV dose of dexamethasone
Systemic steroid (or NSAID) for pain and inflammation
Ocular lubrication
Soft food
When should response to therapy for orbital cellulitis/abscess be? Prognosis?
Within 2-3 days
Prognosis good
What typically causes a mucocele?
Head trauma
What typically causes a retention cyst?
An obstruction of the duct and retention of saliva
What clinical findings are associated with a mucocele and/or a retention cyst?
Unilateral exophthalmos Elevated third eyelid Resistant to retropulsion Fluctuant. nonpainful swelling Yellow and tenacious fluid from an FNA
How do you treat a mucocele?
Surgical excision (orbitotomy) or inject sclerosing agent (Polidocanol)
How do you treat a salivary retention cyst?
Drain cyst and treat oral disease
What is masticatory muscle myosistis?
Swelling of the muscles of mastication - displaces the globes anteriorly
T/F: Masticatory Muscle Myositits has a suspect immune-mediated mechanism component
True
What breeds are over-represented for masticatory muscle myositis?
German Shepherds, Weimeraners, Labrador and Golden Retrievers
What history is associated with masticatory muscle myositis?
Acute onset bilateral protruding eyes and anorexia
What clinical findings are consistent with masticatory muscle myositis?
Bilateral exophthalmos and elevated third eyelid
Resistance to globe retropulsion
Swelling of masticatory muscles
Jaw movements are restricted and very painful
Fever
What additional diagnostics can be done to diagnose masticatory muscle myositis?
CBC, creatine phosphokinase, biopsy of temporal muscles
What will a CBC show in a patient with masticatory muscle myositis?
Leukocytosis with marked eosinophilia
What will the creatine phosphokinase levels be like in masticatory muscle myositis patients?
Elevated - in the acute phase
What will histopath reveal from temporal muscles in patients with masticatory muscle myositis?
Degenerate muscle fibers, neutrophilic and eosinophilic infiltration
Make sure to test for autoantibodies to myofibers 2M
How is masticatory muscle myositis treated?
Oral steroid (immunosuppressive dose) for 1 month then taper slowly
What complications are associated with masticatory muscle myositis?
Possible recurrence
If uncontrolled, it could lead to fibrosis and muscle atrophy
What is extraocular polymyositis?
Swelling of the extraocular muscles
What is the signalment for extraocular polymyositis?
Young golden retrievers +/- others
Intact females are over-represented
What clinical findings are associated with extraocular polymyositis?
Bilateral painless exophthalmos Significant scleral show No third eyelid elevation Normal to near normal globe retropulsion vision may be affected
How is extraocular polymyositis diagnosed?
Typically based on signalment and exam
Can do an MRI if you wish
How is extraocular polymyositis treated?
Systemic corticosteroid
Oral cyclosporine - start every day and then taper
What complications are associated with extraocular polymyositis?
Possible recurrence and enophthalmos
T/F: Most orbital neoplasias are benign.
False - they are mainly malignant
What is the signalment for orbital neoplasia?
Generally an older patient with slowly progressive changes
What clinical findings are associated with orbital neoplasia?
Unilateral exophthalmos Elevated third eyelid Decreased retropulsion Scleral indentation may be visible on fundic exam Usually NOT PAINFUL
How is orbital neoplasia diagnosed?
Complete PE, thoracic rads, ocular/orbital ultrasound, FNA/biopsy of lesion, and CT/MRI for lesion localization and surgical planning
What are the treatment options for orbital neoplasia
Orbitotomy and mass excision (refer)
Exenteration or radical orbitectomy
Euthanasia if advanced
What is the prognosis for orbital neoplasia?
Poor to guarded at best
What are some ‘other’ causes of orbital disease?
Vascular anomalies, parasitic cyst, orbital hematoma, and orbital trauma/fractures
If orbital hematomas are also associated with extensive bilateral or unilateral subconjunctival hemorrhage, what should you suspect is the cause?
rodenticide toxicity
Overall, what are the most frequent orbital diseases?
Tumors, trauma, abscesses, and inflammation/cellulitis
What is ocular proptosis?
When eyelids become locked behind the globe equator
What causes ocular proptosis?
Trauma - HBC, dog fight, kicked by horse, exam restraint
T/F: Ocular proptosis is a true ocular emergency
True
What are the keys to managing ocular proptosis?
Keep the patient calm, ocular lubricant, complete physical exam, complete eye exam, and decide whether to enucleate or surgically reposition eye
What is the procedure for globe replacement?
Perform a lateral canthotomy
Pull the eyelids out, up, and over the globe if possible
Horizontal mattress tarsorrhaphy sutures
Close lateral canthus
What is the prognosis for ocular proptosis?
Fair to good if brachycephalic
If intraocular hemorrhage - guarded for vision
T/F: Pupil size in cases of ocular proptosis is an indicator of prognosis.
False - tis not
If not contradicted, what drug should be given for ocular proptosis management?
Dexamethasone
What post replacement therapy is recommended for ocular proptosis?
E-collar Keep area clean Systemic antibiotic and anti-inflammatory Topical antibiotic +/- atropine Pain meds as needed
How long should sutures be left in post globe replacement after an ocular proptosis situation?
3 weeks
What should be done at the time of suture removal post globe replacement?
Check STT, stain cornea, and examine eye
What complications are possible with ocular proptosis?
Blindness, KCS, lagophthalmos +/- exposure keratitis, lateral strabismus if medial rectus muscle torn, and phthisis bulbi if severe globe trauma
What is an enucleation?
Surgical removal of the globe, eyelid margins, third eyelid, and conjunctiva
+/- silicone orbital prosthesis
What is an exenteration?
Removal of the globe, eyelid margins, and orbital contents
When is an exenteration generally performed?
For malignant orbital neoplasia
What is an evisceration?
Removal of intraocular contents and placement of a silicone prosthesis
When is an evisceration contraindicated?
In cases of neoplasia/infection
What are the steps to a transconjunctival enucleation?
- 360 degree perilimbal incision approximately 5 mm from limbus - dissect down to the level of the sclera, blunt and sharp dissection circumferentially and posterior
- Extra ocular muscles are transected near insertions
- Optic nerve can be clamped prior to transection
- Control hemorrhage by placing gauze in orbit for 5 minutes prior to closure (make sure to remove)
- Remove third eyelid at base, 3-5 mm of the eyelid margins, and remaining conjunctiva
- 2 or 3-layer closure with 3-0 to 5-0 suture
How is a transpalpebral enucleation different than a transconjunctival enucleation?
The eyelids are sutured close or clamped and then the skin around the lids are incised and dissected down to the conjunctival sack, then work posterior to free the globe and remove en bloc
Basically you are taking the eyelids out too - may have a mass
What complications are associated with enucleation?
Hemorrhage, orbital cyst formation, contralateral blindness, seroma, and orbital emphyselma
Hemorrhage due to enucleation can be extensive in species with what?
orbital sinus or plexus
What is an orbital cyst formation post enucleation due to?
Poor surgical technique - there was incomplete removal of secretory tissue
What is done to fix an orbital cyst formation post enucleation?
Surgery to remove remaining secretory tissue
What causes contralateral blindness post enucleation?
Excessive traction is placed on the optic nerve during surgery - damage to optic chiasm
T/F: Contralateral blindness post enucleation is more common in cats and blindness is irreversible.
True - it is due to their shorter optic nerve (the cat part)
Seromas post enuclation are more common in ____ with _____ _____.
cats; orbital implants
Orbital emphysema primarily occurs in _______ dogs. Increased ________ pressure causes air to enter the patent ________ duct while breathing. A ______ is possible of the medial orbital wall. It usually resolves spontaneously.
Brachycephalic; intranasal; nasolacrimal; fracture
Why are orbital prosthesis typically not placed in cases of exenterations?
You want to leave room for mass regrowth if palliative therapy of orbital tumor
What nerve block should be used for enucleatino/exenteration?
Inferior-temporal palpebral approach for the RETROBULBAR block
What post operative care is done for enucleation/exenteration?
Ice pack surgery site
Some bleeding from incision and ipsilateral nostril is normal
Systemic nonsteroidal anti-inflammatory drug and/or other analgesic medication
E-collar if needed
Suture removal in 2 weeks if needed
In what species is an evisceration not recommended in?
cats
What is the technique for an evisceration (this is a referral surgery)?
- Approximately 160 degree incision in dorsal conjunctiva and sclera
- Removal of all intraocular contents
- Silicone prosthesis placed with Carter sphere introducer
- Close with 6-0 Vicryl
- Temporary tarsorrhaphy sutures placed
What is the recommended post operative care for evisceration?
Topical antibiotic
Systemic NSAID
Analgesics
E-collar
Temporary tarsorrhaphy sutures removed 2-3 weeks after surgery
Still can develop ocular disease - corneal ulcers, keratoconjunctivitis
What type of orbit does a dog and cat have?
open
