Orbit Flashcards
What is the function of the orbit?
- Protect the globe
What structures are part of the orbit?
- 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
What are the parts of an Orbital Exam?
- 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
What are the clinical signs of orbital disease?
- Exophthalmos
- Enophthalmos
- Strabismus
- Elevated third eyelid
- Pain on palpation of periorbital area
- Pain on opening mouth
- Exposure keratitis
What is Exophthalmos?
- 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.
What is enophthalmos?
- 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
What is Microphthalmos?
- Congenitally small globe
What is Phthisis bulbi?
- Shrunken globe
- post inflammatory change
What diagnostic tests can be done for orbital diseases?
- 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
How useful are Skull Radiographs in diagnosing orbital disease
- Difficult to interpret
- Useful for:
- Bony lysis or proliferation
- Sinus or nasal disease
- Radio dense foreign bodies
How useful are dental Radiographs in diagnosing orbital disease
- Useful when suspecting dental disease that is infiltrating into the orbit
- i.e. tooth root abscess
How useful is Ultrasound in diagnosing Orbital disease?
- 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
How useful is CT in diagnosing orbital disease?
- Requires general anesthesia
- Useful for:
- 3D orbital imaaging
- Examination of boney details
- orbital fractures
- bony lysis
How useful are MRIs in diagnosing orbital disease?
- Requires general anesthesia
- Useful for:
- 3D orbital imaging
- Detailed soft tissue study
- Contraindicated with metallic foreign bodies
How can Samples be taken from the orbit?
- 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
What are some common Orbital abnormalities and diseases?
- Congenital abnormalities
- Orbital cellulitis/abscess
- Salivary mucocele or cysts
- Masticatory muscle myositis
- Orbital neoplasia
- Ocular proptosis
What are common congenital abnormalities of the orbit?
- Microphthalmos
- Divergent strabismus
- Exotropia
- mainly brachycephalic dogs
- usually no clinical significance
- Convergent Strabismus
- Esotropia
- Inherited in cats
- Autosomal recessive
- primarily in Siamese
What is Orbital Cellulitis/Abscess? Who commonly is affected
- 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
What are the Clinical signs and findings
- Exophthalmos +/- lagophthalmos
- Elevated third eyelid
- Injected conjunctival and episcleral vessels
- Resistant to retropulsion +/- pain
- Pain on periorbital palpations
- Yelps when mouth opened
- Febrile
What are common findings in an oral exam of a patient with orbital cellulitis/abscess
- Swelling +/- fistula caudal to last upper molar tooth
- pterygopalatine fossa
What is the treatment for Orbital Abscesses
- 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
Why would a salivary mucocele/cyst affect the orbit?
- Usually due to trauma
- Saliva leaks from zygomatic salivary gland, causing inflammation and tissue fibrosis
- Results in an encapsulated ‘cyst’
What are the signs of an orbital salivary mucocele/cyst
- Exophthalmos and 3rd eyelid elevation
- No/minimal pain
How are abscesses/neoplasias distinguished from salivary mucocele/cyst in the orbit?
- imaging and sample collection
- aspiration of yellow, tenacious fluid
what is the treatment for a salivary mucocele/cyst in the orbit
- Surgical excision or drainage
- some reports of sclerosing agent injection
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
what are the clinical signs of Masticatory Muscle Myositis?
- Acute onset bilateral exophthalmos
- painful and restrictive jaw movements
- fever
- lethargy
- anorexia
How is Masticatory Muscle Myositis diagnosed
- 2M antibody test
- compatible clinical signs
How is Masticatory Muscle Myositis diagnosed
- Systemic immunosuppression
Where do orbital neolasias originate from?
- Primary from any orbital tissue
- Invasion from adjacent structures
- Metastasize from distant site
What are the clinical findings with Orbital Neoplasia
- Unilateral exophthalmos
- Elevated third eyelid
- Decreased retropulsion
- Scleral indentation on fundic exam
- Usually Not Painful
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
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
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
What is Ocular Proptosis
- Globe moves anteriorly and eyelids become “trapped” behind equator
- True ophthalmic emergency
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
- Most common in brachycephalic dogs
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
- 3 enucleation criteria:
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
- ~1:50 dilution
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
- Remove sutures in 2-3 wks
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)
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)
What is enucleation surgery?
- Surgical removal of globe, third eyelid & gland
- +/- silicone orbital prosthesis
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
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
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
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
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
- uncommon - due to poor surgical technique
- 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
- Excessive traction placed on optic nerve during surgery
What is the post-operative care for orbital evisceration surgery
- Topical and oral antibiotic
- Systemic NSAIDs +/- analgesics
- E-collar
