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Medicine I > Orbit > Flashcards

Orbit Flashcards

1
Q

What is the function of the orbit?

A
  • Protect the globe
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2
Q

What structures are part of the orbit?

A
  • Nerves and blood vessels
  • Extraocular muscles and Orbital fat
  • Third eyelid
  • Lacrimal gland
  • Muscles of mastication, zygomatic salivary gland, medial pterygoid muscle
  • Skull bones - open or closed orbit
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3
Q

What are the parts of an Orbital Exam?

A
  • Visual inspection
    • Symmetry
    • position of third eyelid
    • Position and motility of globe
  • Palpation of orbital rim
  • Retropulsion of globes
  • Vision and PLR assessment
  • Nasal air flow
  • Ability/extent of mouth opening
  • Oral exam
    • caudal to last upper molar
    • sedation/general anesthesia
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4
Q

What are the clinical signs of orbital disease?

A
  • Exophthalmos
  • Enophthalmos
  • Strabismus
  • Elevated third eyelid
  • Pain on palpation of periorbital area
  • Pain on opening mouth
  • Exposure keratitis
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5
Q

What is Exophthalmos?

A
  • Normal sized globe displaced anteriorly/rostrally within the orbit
  • Due to increased orbital volume
  • Numerous causes
    • Neoplasia, abscess/cellulitis, hemorrhage, vascular anomaly, mucocele, cysts, myositis, etc.
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6
Q

What is enophthalmos?

A
  • Normal sized globe displaced posteriorly/caudally within the orbit
  • Due to globe retraction, decreased orbital volume or pressure anterior to the equator of the gobe
  • Numerous causes
    • Pain, msucle wasting, loss of orbital fat, Horner’s syndrome, orbital fractures, dehydration, extraocular muscle fibrosis, adnexal neoplasia
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7
Q

What is Microphthalmos?

A
  • Congenitally small globe
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8
Q

What is Phthisis bulbi?

A
  • Shrunken globe
    • post inflammatory change
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9
Q

What diagnostic tests can be done for orbital diseases?

A
  • Minimum database
  • Imaging studies:
    • skull radiographs
    • Dental Radiographs
    • Orbital/ocular ultrasound
    • Computed tomography (CT)
    • Magnetic resonance imaging (MRI)
  • Orbital sampling
    • FNA and cytology
    • Culture and sensitivity
    • Biopsy and histopathology
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10
Q

How useful are Skull Radiographs in diagnosing orbital disease

A
  • Difficult to interpret
  • Useful for:
    • Bony lysis or proliferation
    • Sinus or nasal disease
    • Radio dense foreign bodies
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11
Q

How useful are dental Radiographs in diagnosing orbital disease

A
  • Useful when suspecting dental disease that is infiltrating into the orbit
    • i.e. tooth root abscess
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12
Q

How useful is Ultrasound in diagnosing Orbital disease?

A
  • Needs Topical anesthetic
  • Ocular ultrasound - 10-13 MHz probe
  • Orbital Ultrasound - 7.5 MHz probe, Doppler
  • Useful for:
    • Cysts and abscesses
    • Vascular anomalies
    • Foreign bodies
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13
Q

How useful is CT in diagnosing orbital disease?

A
  • Requires general anesthesia
  • Useful for:
    • 3D orbital imaaging
    • Examination of boney details
      • orbital fractures
      • bony lysis
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14
Q

How useful are MRIs in diagnosing orbital disease?

A
  • Requires general anesthesia
  • Useful for:
    • 3D orbital imaging
    • Detailed soft tissue study
  • Contraindicated with metallic foreign bodies
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15
Q

How can Samples be taken from the orbit?

A
  • Fine needle aspirate or biopsy
  • Can perform “blind” or w/ ultrasound/CT guidance
  • Many important structures!
  • Approaches:
    • Transconjunctival adjacent to the globe
    • Through skin posterior to orbital ligament
    • Oral
      • Caudal to last molar tooth
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16
Q

What are some common Orbital abnormalities and diseases?

A
  • Congenital abnormalities
  • Orbital cellulitis/abscess
  • Salivary mucocele or cysts
  • Masticatory muscle myositis
  • Orbital neoplasia
  • Ocular proptosis
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17
Q

What are common congenital abnormalities of the orbit?

A
  • Microphthalmos
  • Divergent strabismus
    • Exotropia
    • mainly brachycephalic dogs
    • usually no clinical significance
  • Convergent Strabismus
    • Esotropia
    • Inherited in cats
      • Autosomal recessive
      • primarily in Siamese
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18
Q

What is Orbital Cellulitis/Abscess? Who commonly is affected

A
  • Inflammation of the orbital tissues +/- abscess
  • Common Presenting Signalment and History:
    • Young animal
    • acute onset
    • compatible history (I.e. Stick chewing)
    • Possibly hyporexic or decreased chewing/aversion to hard food
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19
Q

What are the Clinical signs and findings

A
  • Exophthalmos +/- lagophthalmos
  • Elevated third eyelid
  • Injected conjunctival and episcleral vessels
  • Resistant to retropulsion +/- pain
  • Pain on periorbital palpations
    • Yelps when mouth opened
  • Febrile
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20
Q

What are common findings in an oral exam of a patient with orbital cellulitis/abscess

A
  • Swelling +/- fistula caudal to last upper molar tooth
    • pterygopalatine fossa
21
Q

What is the treatment for Orbital Abscesses

A
  • Confirm abscess (imaging)
  • Establish drainage if accessible
    • incise oral mucosa caudal to last upper molar w/ #15 blade
    • Insert closed hemostat, advance slowly, then open
    • Collect samples
      • culture/sensitivity (aerobic & anaerobic) and cytology
    • Leave open to drain
      • may not see a lot of drainage
  • Remove nidus, if present
  • Medical therapy
    • Systemic antibiotics (often mixed aerobic & anaerobic)
      • Cephalosporines (cepfodoxime, Clavamox) & Enrofloxacin are good first choices
    • Systemic NSAID for pain and inflammation
    • Ocular lubrication
      • Can use broad spectrum antibiotic ointment
      • temporary tarsorrhaphy
    • Soft food
  • Response to therapy is usually w/in 2-3 days
  • Prognosis is good
22
Q

Why would a salivary mucocele/cyst affect the orbit?

A
  • Usually due to trauma
  • Saliva leaks from zygomatic salivary gland, causing inflammation and tissue fibrosis
    • Results in an encapsulated ‘cyst’
23
Q

What are the signs of an orbital salivary mucocele/cyst

A
  • Exophthalmos and 3rd eyelid elevation
  • No/minimal pain
24
Q

How are abscesses/neoplasias distinguished from salivary mucocele/cyst in the orbit?

A
  • imaging and sample collection
    • aspiration of yellow, tenacious fluid
25
Q

what is the treatment for a salivary mucocele/cyst in the orbit

A
  • Surgical excision or drainage
  • some reports of sclerosing agent injection
26
Q

What is Masticatory Muscle myositis?

A
  • Immune-mediated inflammation targeting temporalis, masseter, and pterygoid muscles
    • Type 2M myofibers
  • Breed predisposition
    • Golden and Labrador Retrievers
    • German Shepherds
    • Weimeraners
27
Q

what are the clinical signs of Masticatory Muscle Myositis?

A
  • Acute onset bilateral exophthalmos
  • painful and restrictive jaw movements
  • fever
  • lethargy
  • anorexia
28
Q

How is Masticatory Muscle Myositis diagnosed

A
  • 2M antibody test
  • compatible clinical signs
29
Q

How is Masticatory Muscle Myositis diagnosed

A
  • Systemic immunosuppression
30
Q

Where do orbital neolasias originate from?

A
  • Primary from any orbital tissue
  • Invasion from adjacent structures
  • Metastasize from distant site
31
Q

What are the clinical findings with Orbital Neoplasia

A
  • Unilateral exophthalmos
  • Elevated third eyelid
  • Decreased retropulsion
  • Scleral indentation on fundic exam
  • Usually Not Painful
32
Q

How are Orbital Neoplasias diagnosed?

A
  • Complete physical exam
  • Thoracic radiographs (metastasis)
  • Orbital ultrasound
  • CT/MRI for lesion localization and surgical planning
  • FNA/biopsy of lesions
33
Q

What is the treatment for orbital neoplasias?

A
  • Orbitotomy and mass excision (referral)
  • Exenteration or radical orbitectomy
    • +/- radiation therapy and/or chemotherapy
    • Enucleation or exenteration may also be performed as a palliative measure
  • Euthanasia if advanced disease
34
Q

What is the prognosis of orbital neoplasia

A
  • Guarded to poor
  • Survival time increases w/ early diagnosis and surgical therapy
    • <1yr in dogs
    • ~1mo in cats
35
Q

What is Ocular Proptosis

A
  • Globe moves anteriorly and eyelids become “trapped” behind equator
  • True ophthalmic emergency
36
Q

What causes Ocular Proptosis?

A
  • Caused by trauma
    • Hit By Car, dog fight, kicked by horse
  • Degree of trauma needed varies:
    • Most common in brachycephalic dogs
      • shallow orbit and large palpebral fissure
      • Minimal trauma needed
    • Prognosis very poor in horses, cats, and dolicocephalic dogs
      • severe trauma necessary
37
Q

How is Ocular Proptosis managed?

A
  • Ocular lubricant & E-collar
    • KY Jelly, artificial tears, eyewash, Vaseline, cooking oil, etc
  • Complete physical exam - assess for other injuries
  • Complete eye exam
  • Decide whether to enucleate or surgically reposition eye
    • 3 enucleation criteria:
      • 3 or more EOMs torn
      • Optic nerve transected
      • Globe (cornea and/or sclera) ruptured
38
Q

How is the globe prepped for surgery following Ocular Proptosis?

A
  • Keep eye lubricated
  • Carefully clip eyelid hair
  • Cleanse area with dilute betadine solution
    • ~1:50 dilution
      • 5ml 5% betadine in 250 ml saline
    • NOT betadine scrub or chlorhexidine - toxic to cornea
39
Q

What is the treatment for Ocular Proptosis following surgery?

A
  • Medications:
    • oral antibiotic
    • Oral NSAID
    • Topical antibiotic
    • Topical atropine
    • Pain meds as needed
  • E-collar
  • Keep area clean
  • Rechecks
    • Remove sutures in 2-3 wks
      • staged removal may be necessary
40
Q

What is the Prognosis following Ocular Proptosis?

A
  • Good - brachycephalic and minor trauma
  • Guarded for vision w/ intraocular hemorrhage
  • Pupil size is not an indicator of prognosis
    • is Direct or consensual PLR present - prognosis is good
  • Vision prognosis varies (~20% have some vision)
41
Q

What are possible complications of Ocular Proptosis?

A
  • Blindness
  • Strabismus
    • Primarily lateral strabismus
  • Lagophthalmus ⇢ exposure keratitis
  • Decreased corneal sensation
  • Keratoconjunctivitis sicca (dry eye disease)
  • Glaucoma or phthisis bulbi (severe intraocular damage)
42
Q

What is enucleation surgery?

A
  • Surgical removal of globe, third eyelid & gland
  • +/- silicone orbital prosthesis
43
Q

What is orbital evisceration surgery?

A
  • Removal of intraocular contents and placement of a silicone prosthesis in corneo-scleral shell
  • Contraindicated in cases of neoplasia or infectious intraocular disease process
  • Not recommended in cats - increased implant extrusion risk
44
Q

What is orbital exteneration surgery?

A
  • Removal of globe and all orbital soft tissues
    • transpalpebral approach
    • Routine skin closure
  • Generally performed for orbital neoplasia
    • Submit tissue for hitopathology
45
Q

What are the different surgical approaches for Enucleation surgery?

A
  • Transconjunctival Enucleation
    • Widen lateral canthus
    • Remove eyeball and nictitating membrane
    • incise eyelids and suture closed
  • Transpalpebral Approach
    • indications: surface ocular infection or neoplasia
    • Suture eyelids closed
    • Incise skin around lids and dissect down to sclera, then work posterior
46
Q

What is the post-operative care for Enucleation surgery

A
  • Cold compress (BID - TID for 10-15 minutes if tolerated)
  • Some bleeding from incision and ipsilateral nostril is expected
  • Systemic nonsteroidal anti-inflammatory drug and/or other analgesic medication
  • E-collar if needed
  • Suture removal in 2 weeks
47
Q

What are the Post-op complications of Enucleation surgery

A
  • Bleeding from incision
    • expected for a few days after surgery
    • Keep in confined, easily cleaned space
  • Infection
  • Cyst formation
    • uncommon - due to poor surgical technique
      • Incomplete removal of secretory tissue
    • Surgery to remove remaining secretory tissue
  • Contralateral Blindness
    • Excessive traction placed on optic nerve during surgery
      • damage to optic chiasm
    • More common in cats (neuro-anatomy)
    • Blindness is usually irreversible
    • Avoid w/ gentle surgical practices
48
Q

What is the post-operative care for orbital evisceration surgery

A
  • Topical and oral antibiotic
  • Systemic NSAIDs +/- analgesics
  • E-collar

Medicine I (43 decks)

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