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Ophthalmology Rotation > The Orbit > Flashcards

The Orbit Flashcards

1
Q

Orbital Anatomy

A
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2
Q

Orbital Exam

A
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3
Q

the orbit (meekins)

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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4
Q

the orbit (meekins)

Exophthalmos

A
  • Normal sized globe displaced anteriorly/rostrally within the orbit
  • Due to increased orbital volume
  • Numerous causes
    • Neoplasia, abscess/cellulitis, hemorrhage, vascular anomaly, mucocoele, cyst, myositis, etc.
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5
Q

the orbit (meekins)

Important to differentiate exophthalmos from:

A

proptosis (an eye that is protruding outside the orbit, usually due to trauma)

exophthalmos (an eye that is pushed forward relative to its normal position, but is still in the orbit)

buphthalmos (an enlarged, glaucomatic globe)

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6
Q

the orbit (meekins)

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 globe
  • Numerous causes
    • Pain, muscle wasting, loss of orbital fat, Horner’s syndrome, orbital fractures, dehydration, extraocular muscle fibrosis, adnexal neoplasia
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7
Q

the orbit (meekins)

Important to differentiate enophthalmos from:

A
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8
Q

Orbital Disease Diagnostic Tests

A
  • Minimum database
  • Imaging studies*
    • Skull radiographs
    • Dental radiographs
    • Orbital/ocular ultrasound
    • Computed tomography (CT)
    • Magnetic resonance imaging (MRI)
  • Orbital sampling
    • Fine needle aspirate and cytology
    • Culture and sensitivity
    • Biopsy and histopathology
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9
Q

the orbit (meekins)

Skull Radiographs

A
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10
Q

the orbit (meekins)

Ultrasound

A
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11
Q

the orbit (meekins)

Computed Tomography (CT)

A
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12
Q

the orbit (meekins)

Magnetic Resonance Imaging (MRI)

A
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13
Q

Orbital Sampling

A
  • Fine needle aspirate or biopsy
  • Can perform “blind” or with ultrasound/CT guidance
  • Remember the anatomy
    • Many very important structures!
  • Approaches
    • Transconjunctival adjacent to globe
    • Through skin posterior to orbital ligament
    • Oral
      • Caudal to last molar tooth
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14
Q

Orbital Abnormalities/Diseases

A

• Congenital abnormalities
• Orbital cellulitis/abscess
• Salivary mucocele or cyst
• Masticatory muscle myositis
• Orbital neoplasia
• Ocular proptosis

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15
Q

Congenital Abnormalities

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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16
Q

the orbit (meekins)

Orbital Cellulitis/Abscess

  • what
  • signalment and history
  • clinical signs
  • exam
A
  • Inflammation of the orbital tissues +/- abscess
  • Signalment and history
    • Young animal, acute onset, compatible history (“stick chewer”)
    • Possibly hyporexic or decreased chewing/aversion to hard food
  • Clinical signs and findings
    • Exophthalmos +/- lagophthalmos
    • Elevated third eyelid
    • Injected conjunctival and episcleral vessels
    • Resistant to retropulsion +/- painful
    • Pain on periorbital palpation, yelps when mouth opened!
    • Febrile
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17
Q

Orbital Abscess Treatment

A
  • Confirm abscess (imaging)
  • Establish drainage if accessible
    • Incise oral mucosa caudal to last upper molar with #15 Bard-Parker 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
    • Ex. foreign body, tooth
  • Medical therapy
    • Systemic antibiotics (often mixed aerobic & anaerobic)
      • Cephalosporins (cefpodoxime, Clavamox) & Enrofloxacin are good first choices
    • Systemic NSAID for pain and inflammation
    • Ocular lubrication
      • Can use broad spectrum antibiotic ointment (i.e. NeoPolyBac)
      • Temporary tarsorrhaphy?
    • Soft food
  • Response to therapy is usually within 2-3 days
  • Prognosis is good
18
Q

Salivary Mucocele/Cyst

A
  • Usually due to trauma
    • Saliva leaks from zygomatic salivary gland, causing inflammation and tissue fibrosis
      • Results in an encapsulated ‘cyst’
  • Signs of orbital disease
    • Exophthalmos and TEL elevation
    • Minimally or non-painful
  • Distinguished from abscess or neoplasia by imaging and sample collection
    • Aspiration of yellow, tenacious fluid
  • Treatment
    • Surgical excision or drainage
    • Some reports of sclerosing agent injection
19
Q

the orbit (meekins)

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
  • Clinical signs:
    • Acute onset bilateral exophthalmos, painful and restrictive jaw movements, fever, lethargy, anorexia
  • Diagnosis: 2M antibody test, compatible clinical signs
  • Treatment: systemic immunosuppression
20
Q

the orbit (meekins)

Orbital Neoplasia

  • origin
  • signalment and history
  • clinical findings
A
  • Origin
    • Primary from any orbital tissue
    • Invasion from adjacent structures
    • Metastasize from distant site
  • Signalment and history
    • Generally older patients
    • Slowly progressive changes
  • Clinical findings
    • Unilateral exophthalmos
    • Elevated third eyelid
    • Decreased retropulsion
    • Scleral indentation on fundic exam
    • Usually NOT PAINFUL
21
Q

the orbit (meekins)

Orbital Neoplasia

  • diagnostics
  • treatment
  • prognosis
A
  • Diagnostics
    • Complete physical exam
    • Thoracic radiographs (met check)
    • Orbital ultrasound
    • CT/MRI for lesion localization and surgical planning
    • FNA/biopsy of lesion
  • Treatment
    • 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
  • Prognosis
    • Guarded to poor
    • Survival time increases with early diagnosis and surgical therapy
      • Less than 1 year in dogs, ~ 1 month in cats
22
Q

the orbit (meekins)

Exophthalmos Clues

  • think inflammatory if…
  • think neoplasia if…
  • if bilateral?
A
  • Think inflammatory disease…
    • If younger animal
    • If painful
    • If rapid onset
    • If febrile
  • Think neoplasia…
    • If older animal
    • If slow onset
  • If bilateral…think myositis or multicentric neoplasia (lymphosarcoma)
  • But not all patients read the textbooks!!
23
Q

the orbit (meekins)

Ocular Proptosis

  • what
  • caused by…
A
  • Globe moves anterior and eyelids become “trapped” behind equator
    • True ophthalmic emergency!!!
  • Caused by trauma
    • HBC, dog fight, kicked by horse
    • Degree of trauma needed to cause proptosis varies
      • Most common in brachycephalic dogs
        • Shallow orbit and large palpebral fissure
        • Minimal trauma needed (even exam restraint can be a cause!)
      • Prognosis very poor in horses, cats, and dolicocephalic dogs
        • Severe trauma necessary
24
Q

the orbit (meekins)

Ocular Proptosis

  • Keys to management
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 transsected
      • Globe (cornea and/or sclera) ruptured
25
Q

the orbit (meekins)

Ocular Proptosis Treatment

  • surgical?
A

Globe replacement

  • General anesthesia
  • Prep
    • Keep eye lubricated!
    • Carefully clip eyelid hair
    • Cleanse area with dilute betadine solution
      • ~1:50 dilution: 5 ml 5% betadine in 250 ml saline
      • Not betadine scrub or chlorhexidine – toxic to cornea
26
Q

the orbit (meekins)

Ocular Proptosis Treatment

  • non-surgical?
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 weeks
    • Staged removal?
27
Q

the orbit (meekins)

Ocular Proptosis Treatment

  • when in doubt…
  • prognosis
A
  • When in doubt, replace the globe
    • You can always take it out, but you can never put it back!
  • Prognosis
    • Good in general if brachycephalic and minor trauma
    • Guarded for vision with intraocular hemorrhage
    • Pupil size is not an indicator of prognosis
    • But if direct or consensual PLR present, prognosis is good
    • Vision prognosis varies (~20% have some vision)
    • Better prognosis for saving globe
    • Many owners value globe for cosmesis
28
Q

Ocular Proptosis Complications
• Complications/sequelae

A
  • Blindness
  • Strabismus
    • Primarily lateral strabismus
  • Lagophthalmos (inability to blink completely)
    • Exposure keratitis
  • Decreased corneal sensation
  • Keratoconjunctivitis sicca (dry eye disease)
  • Glaucoma or phthisis bulbi (if severe intraocular damage)
29
Q

the orbit (meekins)

Ocular Proptosis Treatment

  • Keys to remember
A
  • Assess and treat the whole animal
  • Keep eye moist!
  • Rapid globe replacement if possible
  • When in doubt, replace the globe!
30
Q

the orbit (meekins)

Orbital Surgery

  • Enucleation (what)
A
  • Surgical removal of globe, third eyelid & gland
  • +/- silicone orbital prosthesis
31
Q

the orbit (meekins)

Orbital Surgery

• Evisceration (what)

A
  • Removal of intraocular contents and placement of a silicone prosthesis in corneo-scleral shell
  • Contraindicated in cases of neoplasia/infection
32
Q

the orbit (meekins)

Orbital Surgery

• Exenteration (what)

A
  • Removal of globe and all orbital contents
  • Generally performed for orbital neoplasia
33
Q

the orbit (meekins)

Transconjunctival Enucleation

A
34
Q

the orbit (meekins)

Transpalpebral Enucleation

A
  • Indications: surface ocular infection or neoplasia
  • Suture eyelids closed
  • Incise skin around lids and dissect down to sclera, then work posterior
35
Q

Enucleation
• Post-operative care

A
  • Cold compress (ice pack) applied to surgery site
    • B-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
  • Elizabethan collar if needed (usually not in cats)
  • Suture removal in 2 weeks
36
Q

Enucleation Post-op Complications

A
  • Bleeding from incision
    • Expected for a few days after surgery
    • Keep dog in confined, easily cleaned space
  • Infection
  • Cyst formation
    • Uncommon but due to poor surgical technique
    • Incomplete removal of secretory tissue
    • Surgery is performed to remove remaining secretory tissue
  • Contralateral blindness
    • Excessive traction placed on optic nerve during surgery
      • Damage to optic chiasm
    • More common in cats (due to neuro-anatomy)
    • Blindness is usually irreversible
    • Avoid with gentle surgical practices!!!
37
Q

the orbit (meekins)

Evisceration

  • technique
  • indication
A
38
Q

Evisceration Post-operative Care

A
  • Topical and oral antibiotic
  • Systemic NSAID +/- analgesics
  • E-collar
  • Can still develop ocular surface disease that requires future treatment!
  • Corneal ulcers
  • Keratoconjunctivitis sicca
39
Q

the orbit (meekins)

Exenteration

  • indications
A
  • Remove globe and all orbital soft tissues
    • VS. enucleation (fat/muscle left behind in orbit)
    • Transpalpebral approach
    • Routine skin closure
  • Used in cases of extensive neoplasia
  • Submit tissues for histopathology
40
Q

Summary

  • *• Clinical signs of orbital disease:**
  • *• Orbital inflammation?**
  • *• Orbital neoplasia?**
  • *• Ocular proptosis?**
  • *• Enucleation?**
  • *• Evisceration?**
  • *• Exenteration?**
A
  • Clinical signs of orbital disease:
    • Exophthalmos
    • Third eyelid elevation
  • Orbital inflammation (abscess/cellulitis) occurs in young dogs, is acute & painful, and results in fever, leukocytosis
  • Orbital neoplasia occurs in older dogs, is non-painful and slowly progressive
  • Ocular proptosis is a true ophthalmic emergency
    • When in doubt, always attempt replacement with tarsorrhaphy
  • Enucleation involves complete removal of globe and adnexa
  • Evisceration is a cosmetic alternative to enucleation
  • Exenteration is necessary in cases of advanced orbital neoplasia

Ophthalmology Rotation (20 decks)

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