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Ophthalmology > Unit 1 - Orbit > Flashcards

Unit 1 - Orbit Flashcards

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
Q

What is the signalment for orbital cellulitis/abscess?

A

Young animal, acute onset, ‘chews sticks’

Possibly inappetant or decreased playing/chewing

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26
Q

What are some possible clinical signs for orbital cellulitis/abscess?

A 
Unilateral exophthalmos +/- lagophthalmos
Elevated third eyelid
Injected conjunctival vessels
Resistant to retropulsion +/- painful
Pain on periorbital palpation
Yelps when mouth opened
Febrile
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27
Q

Orbital abscesses must be confirmed before treatment, how would you do that?

A

ultrasound or MRI

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28
Q

How do you drain an orbital abscess if accessible?

A

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

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29
Q

What is the medical therapy for orbital cellulitis/abscess?

A

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

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30
Q

When should response to therapy for orbital cellulitis/abscess be? Prognosis?

A

Within 2-3 days

Prognosis good

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31
Q

What typically causes a mucocele?

A

Head trauma

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32
Q

What typically causes a retention cyst?

A

An obstruction of the duct and retention of saliva

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33
Q

What clinical findings are associated with a mucocele and/or a retention cyst?

A 
Unilateral exophthalmos
Elevated third eyelid
Resistant to retropulsion
Fluctuant. nonpainful swelling
Yellow and tenacious fluid from an FNA
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34
Q

How do you treat a mucocele?

A

Surgical excision (orbitotomy) or inject sclerosing agent (Polidocanol)

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35
Q

How do you treat a salivary retention cyst?

A

Drain cyst and treat oral disease

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36
Q

What is masticatory muscle myosistis?

A

Swelling of the muscles of mastication - displaces the globes anteriorly

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37
Q

T/F: Masticatory Muscle Myositits has a suspect immune-mediated mechanism component

A

True

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38
Q

What breeds are over-represented for masticatory muscle myositis?

A

German Shepherds, Weimeraners, Labrador and Golden Retrievers

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39
Q

What history is associated with masticatory muscle myositis?

A

Acute onset bilateral protruding eyes and anorexia

40
Q

What clinical findings are consistent with masticatory muscle myositis?

A

Bilateral exophthalmos and elevated third eyelid
Resistance to globe retropulsion
Swelling of masticatory muscles
Jaw movements are restricted and very painful
Fever

41
Q

What additional diagnostics can be done to diagnose masticatory muscle myositis?

A

CBC, creatine phosphokinase, biopsy of temporal muscles

42
Q

What will a CBC show in a patient with masticatory muscle myositis?

A

Leukocytosis with marked eosinophilia

43
Q

What will the creatine phosphokinase levels be like in masticatory muscle myositis patients?

A

Elevated - in the acute phase

44
Q

What will histopath reveal from temporal muscles in patients with masticatory muscle myositis?

A

Degenerate muscle fibers, neutrophilic and eosinophilic infiltration
Make sure to test for autoantibodies to myofibers 2M

45
Q

How is masticatory muscle myositis treated?

A

Oral steroid (immunosuppressive dose) for 1 month then taper slowly

46
Q

What complications are associated with masticatory muscle myositis?

A

Possible recurrence

If uncontrolled, it could lead to fibrosis and muscle atrophy

47
Q

What is extraocular polymyositis?

A

Swelling of the extraocular muscles

48
Q

What is the signalment for extraocular polymyositis?

A

Young golden retrievers +/- others

Intact females are over-represented

49
Q

What clinical findings are associated with extraocular polymyositis?

A 
Bilateral painless exophthalmos
Significant scleral show
No third eyelid elevation
Normal to near normal globe retropulsion
vision may be affected
50
Q

How is extraocular polymyositis diagnosed?

A

Typically based on signalment and exam

Can do an MRI if you wish

51
Q

How is extraocular polymyositis treated?

A

Systemic corticosteroid

Oral cyclosporine - start every day and then taper

52
Q

What complications are associated with extraocular polymyositis?

A

Possible recurrence and enophthalmos

53
Q

T/F: Most orbital neoplasias are benign.

A

False - they are mainly malignant

54
Q

What is the signalment for orbital neoplasia?

A

Generally an older patient with slowly progressive changes

55
Q

What clinical findings are associated with orbital neoplasia?

A 
Unilateral exophthalmos
Elevated third eyelid
Decreased retropulsion
Scleral indentation may be visible on fundic exam
Usually NOT PAINFUL
56
Q

How is orbital neoplasia diagnosed?

A

Complete PE, thoracic rads, ocular/orbital ultrasound, FNA/biopsy of lesion, and CT/MRI for lesion localization and surgical planning

57
Q

What are the treatment options for orbital neoplasia

A

Orbitotomy and mass excision (refer)
Exenteration or radical orbitectomy
Euthanasia if advanced

58
Q

What is the prognosis for orbital neoplasia?

A

Poor to guarded at best

59
Q

What are some ‘other’ causes of orbital disease?

A

Vascular anomalies, parasitic cyst, orbital hematoma, and orbital trauma/fractures

60
Q

If orbital hematomas are also associated with extensive bilateral or unilateral subconjunctival hemorrhage, what should you suspect is the cause?

A

rodenticide toxicity

61
Q

Overall, what are the most frequent orbital diseases?

A

Tumors, trauma, abscesses, and inflammation/cellulitis

62
Q

What is ocular proptosis?

A

When eyelids become locked behind the globe equator

63
Q

What causes ocular proptosis?

A

Trauma - HBC, dog fight, kicked by horse, exam restraint

64
Q

T/F: Ocular proptosis is a true ocular emergency

A

True

65
Q

What are the keys to managing ocular proptosis?

A

Keep the patient calm, ocular lubricant, complete physical exam, complete eye exam, and decide whether to enucleate or surgically reposition eye

66
Q

What is the procedure for globe replacement?

A

Perform a lateral canthotomy
Pull the eyelids out, up, and over the globe if possible
Horizontal mattress tarsorrhaphy sutures
Close lateral canthus

67
Q

What is the prognosis for ocular proptosis?

A

Fair to good if brachycephalic

If intraocular hemorrhage - guarded for vision

68
Q

T/F: Pupil size in cases of ocular proptosis is an indicator of prognosis.

A

False - tis not

69
Q

If not contradicted, what drug should be given for ocular proptosis management?

A

Dexamethasone

70
Q

What post replacement therapy is recommended for ocular proptosis?

A 
E-collar
Keep area clean
Systemic antibiotic and anti-inflammatory
Topical antibiotic +/- atropine
Pain meds as needed
71
Q

How long should sutures be left in post globe replacement after an ocular proptosis situation?

A

3 weeks

72
Q

What should be done at the time of suture removal post globe replacement?

A

Check STT, stain cornea, and examine eye

73
Q

What complications are possible with ocular proptosis?

A

Blindness, KCS, lagophthalmos +/- exposure keratitis, lateral strabismus if medial rectus muscle torn, and phthisis bulbi if severe globe trauma

74
Q

What is an enucleation?

A

Surgical removal of the globe, eyelid margins, third eyelid, and conjunctiva
+/- silicone orbital prosthesis

75
Q

What is an exenteration?

A

Removal of the globe, eyelid margins, and orbital contents

76
Q

When is an exenteration generally performed?

A

For malignant orbital neoplasia

77
Q

What is an evisceration?

A

Removal of intraocular contents and placement of a silicone prosthesis

78
Q

When is an evisceration contraindicated?

A

In cases of neoplasia/infection

79
Q

What are the steps to a transconjunctival enucleation?

A
  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
  6. 2 or 3-layer closure with 3-0 to 5-0 suture
80
Q

How is a transpalpebral enucleation different than a transconjunctival enucleation?

A

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
Q

What complications are associated with enucleation?

A

Hemorrhage, orbital cyst formation, contralateral blindness, seroma, and orbital emphyselma

82
Q

Hemorrhage due to enucleation can be extensive in species with what?

A

orbital sinus or plexus

83
Q

What is an orbital cyst formation post enucleation due to?

A

Poor surgical technique - there was incomplete removal of secretory tissue

84
Q

What is done to fix an orbital cyst formation post enucleation?

A

Surgery to remove remaining secretory tissue

85
Q

What causes contralateral blindness post enucleation?

A

Excessive traction is placed on the optic nerve during surgery - damage to optic chiasm

86
Q

T/F: Contralateral blindness post enucleation is more common in cats and blindness is irreversible.

A

True - it is due to their shorter optic nerve (the cat part)

87
Q

Seromas post enuclation are more common in ____ with _____ _____.

A

cats; orbital implants

88
Q

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.

A

Brachycephalic; intranasal; nasolacrimal; fracture

89
Q

Why are orbital prosthesis typically not placed in cases of exenterations?

A

You want to leave room for mass regrowth if palliative therapy of orbital tumor

90
Q

What nerve block should be used for enucleatino/exenteration?

A

Inferior-temporal palpebral approach for the RETROBULBAR block

91
Q

What post operative care is done for enucleation/exenteration?

A

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
Q

In what species is an evisceration not recommended in?

A

cats

93
Q

What is the technique for an evisceration (this is a referral surgery)?

A
  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
Q

What is the recommended post operative care for evisceration?

A

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
Q

What type of orbit does a dog and cat have?

A

open

Ophthalmology (13 decks)

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