Orbit Flashcards
What do you call the supportive structure of the eye that contain the eyeball, extraocular muscles, fat, vessels, nerves, and fascia?
Periorbital cone
What sinuses surround the orbit?
Frontal and maxillary
Inflammation of what salivary gland can lead to displacement of the globe?
Zygomatic
What are the muscles of mastication?
Masseter
Temporalis
Pterygoid
What bony structure can compress inflamed orbital soft tissue causing severe pain?
Paramus of the mandible
Why do we avoid mouth gags in cats?
Risk of blindness
If mouth is opened to widely Ramus of manbidle compresses maxillary and carotid artery, reducing blood flow
What nerves exit the optic canal??
CN2 optic
Which nerves exit the orbital fissure?
CN III - oculomoror
CN IV - trochlear
CN V - ophthalmic branch of trigeminal
CN VI- abducens
What is cavernous sinus syndrome?
Venous sinus located near the orbital fissure that allows passage of ophthalmic nerves
Infection/inflammation/neoplasia/vascular disorders can disrupt nerve function leading to the following clinical signs..
External ophthalmoplegia Internal ophthalamoplegia Ptosis Reduced corneal and medial canthal sensation Reduced lateral canthal sensation
T/f: both cats and dogs have an orbital ligament that forms the boundary of the orbital rim
True
What features of the brachycephalic skull make them very susceptible to trauma related ocular diseases??
Relative to skull size, the orbital ligament spans a greater portion of the orbital rim in brachycephalic
Orbit is much shallower in brachycephalic
What species have closed orbital rims?
Cows, horses
What do you call abnormal protrusion of the eye from the orbit?
Exopthalamos
What are clinical signs associated with exopthalmos?
Third eyelid protrusion Facial swelling Soft palate bulging Pain on opening mouth Fever
What are common causes of exopthalmos?
Orbital volume imbalance
Neoplasia * Cellulitis/abscess * Zygomatic salivary gland mucocele Masticatory muscle myositis Extraocular myositis Retrobulbar hemorrhage
What do you call an enlargement of the globe? What is the only cause of this>?
Buphthlamos
Glaucoma
You have a dog with exophthalamos.. what will your diagnostic approach be?
Complete ophthalmic exam
- test orbital symmetry
- oral exam
CBC and Chem
Chest rads
Advanced imaging
Tissue sampling
-FNA or biopsy
You discover your patient has as orbital neoplasia. What two treatment methods are there?
Globe sparing — palliative, radiation, surgical exploration, chemo
Globe removal
- enucleation — removal of the eye
- exenteration — removal of the eye and all orbital contents
Your patient has orbital cellulitis/abscess. What two treatments are available ?
Medical
- NSAIDS and antibiotics
Surgical exploration/ drainage
What do you call an abnormal recession of the eye within the orbit?
Enophthalamos
Common clinical signs of enophthalamos?
Facial muscular loss
Third eyelid protrusion
Entropion
What are three common mechanisms of enophthalamos ?
Orbital volume imbalance
Eg dehydration, emaciation, myopathies, space occupying lesion of anterior globe
Active globe retraction
Eg ocular pain — retractor bulbi muscle
Passive glob retraction
Eg horners syndrome — loss of sympathetic tone
What do you call a congenitally small globe?
Microphthalamos
Seen in collies
What do you call an aquired shrunken globe, usually from severe/chronic inflammation?
Phthisis bulbi
What do you call a deviation of one or both eyes, so that both eyes are not directed at same object?
Strabismus
Congenital causes of strabismus?
Congenital
- “normal” variation of brachycephalic
- Siamese cats - convergent, abnormal visual processing
- hydrocephalus— ventrolateral divergent, abnormal orbital volume
Acquired causes of strabismus?
Mechanical or nervous dysfutnion of any rectus muscle
CN III - dorsal, ventral, medial rectus m and ventral oblique
CN IV - dorsal oblique
CN VI - retractor bulbi and lateral rectus
Imbalance in orbital volume
What do you call an anterior displacement of the globe, such that the eyelids are caught behind the equator of the globe ?
What breed is this common in?
Proptosis
Brachycephalic breeds — involves minimal trauma
T/F: brachycephalic have a better prognosis after proptosis than dolichocephalic dogs
True
What features make a poor prognosis for proptosis?
Cats Dolichocepalic > 3 extraocular muscles torn Ruptured eye Hyphens orbital fractures
T/F: most dogs regain vision in the affected eye after proptosis
False
75-80% will be blind in the affected eye
Triage for proptosis?
Lubricate corneal
- triple antibiotic ointment or artificial tear ointment
- e collar
- minimize restraint
- pain managment, sedation or anesthesia
How is the eye put back into place after proptosis?
Horizontal mattress sutures in adjacent eyelids—> temporary toarsorrhaphy
Eye is pushed back into eye with dull end of scalpel blade,
Sutures tie lids together
+/-stents
- IV tubing
- red rubber catheters
- rubber bands
What maintenance therapy must you do following treatment of proptosis
Oral antibiotics for potential cellulitis/infection
If ulceration, give topical antibiotics and atropine
steroids or NSAID intra-op or post-op to reduce inflammation
Sutures stay in 3 weeks as cellulitis resolves
E collar!!
What are complications from treatment of proptosis?
Corneal ulceration — misplaced suture
Loosening of suture
Strabismus — Torn musculature
KCS
Blindness
Recurrence
Need for enucleation
