Orbit Flashcards
(48 cards)
1
Q
What is the function of the orbit?
A
- Protect the globe
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
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
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
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.
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
7
Q
What is Microphthalmos?
A
- Congenitally small globe
8
Q
What is Phthisis bulbi?
A
- Shrunken globe
- post inflammatory change
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
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
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
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
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
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
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
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
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
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
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
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
- Systemic antibiotics (often mixed aerobic & anaerobic)
- 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
what is the treatment for a salivary mucocele/cyst in the orbit
* Surgical excision or drainage
* some reports of sclerosing agent injection
26
What is Masticatory Muscle myositis?
* Immune-mediated inflammation targeting temporalis, masseter, and pterygoid muscles
* Type 2M myofibers
* Breed predisposition
* Golden and Labrador Retrievers
* German Shepherds
* Weimeraners
27
what are the clinical signs of Masticatory Muscle Myositis?
* Acute onset bilateral exophthalmos
* painful and restrictive jaw movements
* fever
* lethargy
* anorexia
28
How is Masticatory Muscle Myositis diagnosed
* 2M antibody test
* compatible clinical signs
29
How is Masticatory Muscle Myositis diagnosed
* Systemic immunosuppression
30
Where do orbital neolasias originate from?
* Primary from any orbital tissue
* Invasion from adjacent structures
* Metastasize from distant site
31
What are the clinical findings with Orbital Neoplasia
* Unilateral exophthalmos
* Elevated third eyelid
* Decreased retropulsion
* Scleral indentation on fundic exam
* Usually Not Painful
32
How are Orbital Neoplasias diagnosed?
* Complete physical exam
* Thoracic radiographs (metastasis)
* Orbital ultrasound
* CT/MRI for lesion localization and surgical planning
* FNA/biopsy of lesions
33
What is the treatment for orbital neoplasias?
* 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
What is the prognosis of orbital neoplasia
* Guarded to poor
* Survival time increases w/ early diagnosis and surgical therapy
* \<1yr in dogs
* ~1mo in cats
35
What is Ocular Proptosis
* Globe moves anteriorly and eyelids become “trapped" behind equator
* True ophthalmic emergency
36
What causes Ocular Proptosis?
* 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
How is Ocular Proptosis managed?
* 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
How is the globe prepped for surgery following Ocular Proptosis?
* 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
What is the treatment for Ocular Proptosis following surgery?
* 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
What is the Prognosis following Ocular Proptosis?
* 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
What are possible complications of Ocular Proptosis?
* Blindness
* Strabismus
* Primarily lateral strabismus
* Lagophthalmus ⇢ exposure keratitis
* Decreased corneal sensation
* Keratoconjunctivitis sicca (dry eye disease)
* Glaucoma or phthisis bulbi (severe intraocular damage)
42
What is enucleation surgery?
* Surgical removal of globe, third eyelid & gland
* +/- silicone orbital prosthesis
43
What is orbital evisceration surgery?
* 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
What is orbital exteneration surgery?
* Removal of globe and all orbital soft tissues
* transpalpebral approach
* Routine skin closure
* Generally performed for orbital neoplasia
* Submit tissue for hitopathology
45
What are the different surgical approaches for Enucleation surgery?
* 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
What is the post-operative care for Enucleation surgery
* 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
What are the Post-op complications of Enucleation surgery
* 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
What is the post-operative care for orbital evisceration surgery
* Topical and oral antibiotic
* Systemic NSAIDs +/- analgesics
* E-collar
