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Ophthalmology > Unit 1 - Orbit > Flashcards

Unit 1 - Orbit Flashcards

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1
Q

What are the bones of the orbit?

A

Maxilla, lacrimal, palantine, frontal, sphenoid, and zygomatic

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2
Q

What are the foramen of the caudal orbit?

A

Ethmoidal foramen, optic canal, orbital fissure, and alar foramen (rostral)

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3
Q

What are the glands of the orbit?

A

Lacrimal gland and zygomatic salivary gland

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4
Q

What are the vessels of the orbit?

A

Maxillary artery, deep facial vein, facial vein, anastomolic branch to the ventral external ophthalmic vein, angular vein of the eye

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5
Q

What nerve is in the orbit?

A

Lacrimal nerve

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6
Q

What are the seven extra-ocular muscles?

A

4 rectus muscles - dorsal, ventral, lateral, and medial
2 oblique muscles - dorsal and ventral
1 retractor bulbi muscle

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7
Q

What are the majority of the extra-ocular muscles innervated by?

A

CN III (oculomotor)

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8
Q

What extra-ocular muscle is not innervated by the oculomotor nerve? What are they innervated by

A 
Superior oblique (CN IV)
Lateral rectus and retractor bulbi (CN VI)
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9
Q

What are the components of the orbital exam?

A 
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
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10
Q

What are some possible clinical signs associated with orbital disease?

A

Exophthalmos, enophthalmos, strabismus, elevated third eyelid, conjunctival hyperemia, lagophthalmos, exposure keratitis, pain on palpation f the periorbital area, and pain on opening mouth

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11
Q

What is exophthalmos?

A

Normal sized globe displaced rostrally within the orbit due to increased orbital volume

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12
Q

What can cause exophthalmos?

A

Neoplasia, abscess/cellulitis, hemorrhage, vascular anomaly, mucocele, cyst, myositis, etc.

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13
Q

What is buphthalmos?

A

Enlarged globe

Need to differentiate this from exophthalmos

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14
Q

What is proptosis?

A

Forward displacement with entrapment of the eyelid margins behind the equator of the globe

Need to differentiate this from exophthalmos

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15
Q

T/F - Exophthalmos is a ‘normal’ conformation for brachycephalics.

A

True - their orbits are just normally shallow

Need to differentiate this from exophthalmos

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16
Q

What is enophthalmos?

A

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

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17
Q

What can cause enophthalmos?

A

Pain, Horner’s syndrome, muscle wasting, loss of orbital fat, orbital fractures, dehydration, extraocular muscle fibrosis, and adnexal neoplasia

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18
Q

What is microphthalmos?

A

Congenitally small globe(s)

Need to differentiate this from enophthalmos

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19
Q

What is phthisis bulbi?

A

A shrunken eye occurring after severe inflammation due to cessation of aqueous production

Need to differentiate this from enophthalmos

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20
Q

What procedures can be done for orbital sampling?

A

FNA/cytology and/or biopsy and histopathology

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21
Q

What are the approaches to orbital sampling?

A

Transconjunctival adjacent to the globe
Through the skin posterior to the orbital ligament
Orally caudal to the last upper molar tooth

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22
Q

What is divergent strabismus also known as? In what species is it common in?

A

Exotropia mainly in brachycephalic dogs

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23
Q

What is convergent strabismus also called? In what species is it common in?

A

Esotropia

Inherited in cats (autosomal recessive) - primarily in siamese

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24
Q

What is orbital cellulitis?

A

inflammation of the orbital tissues

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25
What is the signalment for orbital cellulitis/abscess?
Young animal, acute onset, 'chews sticks' | Possibly inappetant or decreased playing/chewing
26
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 ```
27
Orbital abscesses must be confirmed before treatment, how would you do that?
ultrasound or MRI
28
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
29
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
30
When should response to therapy for orbital cellulitis/abscess be? Prognosis?
Within 2-3 days | Prognosis good
31
What typically causes a mucocele?
Head trauma
32
What typically causes a retention cyst?
An obstruction of the duct and retention of saliva
33
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 ```
34
How do you treat a mucocele?
Surgical excision (orbitotomy) or inject sclerosing agent (Polidocanol)
35
How do you treat a salivary retention cyst?
Drain cyst and treat oral disease
36
What is masticatory muscle myosistis?
Swelling of the muscles of mastication - displaces the globes anteriorly
37
T/F: Masticatory Muscle Myositits has a suspect immune-mediated mechanism component
True
38
What breeds are over-represented for masticatory muscle myositis?
German Shepherds, Weimeraners, Labrador and Golden Retrievers
39
What history is associated with masticatory muscle myositis?
Acute onset bilateral protruding eyes and anorexia
40
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
41
What additional diagnostics can be done to diagnose masticatory muscle myositis?
CBC, creatine phosphokinase, biopsy of temporal muscles
42
What will a CBC show in a patient with masticatory muscle myositis?
Leukocytosis with marked eosinophilia
43
What will the creatine phosphokinase levels be like in masticatory muscle myositis patients?
Elevated - in the acute phase
44
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
45
How is masticatory muscle myositis treated?
Oral steroid (immunosuppressive dose) for 1 month then taper slowly
46
What complications are associated with masticatory muscle myositis?
Possible recurrence | If uncontrolled, it could lead to fibrosis and muscle atrophy
47
What is extraocular polymyositis?
Swelling of the extraocular muscles
48
What is the signalment for extraocular polymyositis?
Young golden retrievers +/- others | Intact females are over-represented
49
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 ```
50
How is extraocular polymyositis diagnosed?
Typically based on signalment and exam | Can do an MRI if you wish
51
How is extraocular polymyositis treated?
Systemic corticosteroid | Oral cyclosporine - start every day and then taper
52
What complications are associated with extraocular polymyositis?
Possible recurrence and enophthalmos
53
T/F: Most orbital neoplasias are benign.
False - they are mainly malignant
54
What is the signalment for orbital neoplasia?
Generally an older patient with slowly progressive changes
55
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 ```
56
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
57
What are the treatment options for orbital neoplasia
Orbitotomy and mass excision (refer) Exenteration or radical orbitectomy Euthanasia if advanced
58
What is the prognosis for orbital neoplasia?
Poor to guarded at best
59
What are some 'other' causes of orbital disease?
Vascular anomalies, parasitic cyst, orbital hematoma, and orbital trauma/fractures
60
If orbital hematomas are also associated with extensive bilateral or unilateral subconjunctival hemorrhage, what should you suspect is the cause?
rodenticide toxicity
61
Overall, what are the most frequent orbital diseases?
Tumors, trauma, abscesses, and inflammation/cellulitis
62
What is ocular proptosis?
When eyelids become locked behind the globe equator
63
What causes ocular proptosis?
Trauma - HBC, dog fight, kicked by horse, exam restraint
64
T/F: Ocular proptosis is a true ocular emergency
True
65
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
66
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
67
What is the prognosis for ocular proptosis?
Fair to good if brachycephalic | If intraocular hemorrhage - guarded for vision
68
T/F: Pupil size in cases of ocular proptosis is an indicator of prognosis.
False - tis not
69
If not contradicted, what drug should be given for ocular proptosis management?
Dexamethasone
70
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 ```
71
How long should sutures be left in post globe replacement after an ocular proptosis situation?
3 weeks
72
What should be done at the time of suture removal post globe replacement?
Check STT, stain cornea, and examine eye
73
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
74
What is an enucleation?
Surgical removal of the globe, eyelid margins, third eyelid, and conjunctiva +/- silicone orbital prosthesis
75
What is an exenteration?
Removal of the globe, eyelid margins, and orbital contents
76
When is an exenteration generally performed?
For malignant orbital neoplasia
77
What is an evisceration?
Removal of intraocular contents and placement of a silicone prosthesis
78
When is an evisceration contraindicated?
In cases of neoplasia/infection
79
What are the steps to a transconjunctival enucleation?
1. 360 degree perilimbal incision approximately 5 mm from limbus - dissect down to the level of the sclera, blunt and sharp dissection circumferentially and posterior 2. Extra ocular muscles are transected near insertions 3. Optic nerve can be clamped prior to transection 4. Control hemorrhage by placing gauze in orbit for 5 minutes prior to closure (make sure to remove) 5. Remove third eyelid at base, 3-5 mm of the eyelid margins, and remaining conjunctiva 5. 2 or 3-layer closure with 3-0 to 5-0 suture
80
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
81
What complications are associated with enucleation?
Hemorrhage, orbital cyst formation, contralateral blindness, seroma, and orbital emphyselma
82
Hemorrhage due to enucleation can be extensive in species with what?
orbital sinus or plexus
83
What is an orbital cyst formation post enucleation due to?
Poor surgical technique - there was incomplete removal of secretory tissue
84
What is done to fix an orbital cyst formation post enucleation?
Surgery to remove remaining secretory tissue
85
What causes contralateral blindness post enucleation?
Excessive traction is placed on the optic nerve during surgery - damage to optic chiasm
86
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)
87
Seromas post enuclation are more common in ____ with _____ _____.
cats; orbital implants
88
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
89
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
90
What nerve block should be used for enucleatino/exenteration?
Inferior-temporal palpebral approach for the RETROBULBAR block
91
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
92
In what species is an evisceration not recommended in?
cats
93
What is the technique for an evisceration (this is a referral surgery)?
1. Approximately 160 degree incision in dorsal conjunctiva and sclera 2. Removal of all intraocular contents 3. Silicone prosthesis placed with Carter sphere introducer 4. Close with 6-0 Vicryl 5. Temporary tarsorrhaphy sutures placed
94
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
95
What type of orbit does a dog and cat have?
open

Ophthalmology (13 decks)

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