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70 Cards in this Set
- Front
- Back
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These species have a complete bony orbit.
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Horse, cow, sheep, goat
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These species have an incomplete bony orbit
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Canine, feline, pig
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Why do some carnivorous species have an incomplete bony orbit?
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Allows for wider opening of the mouth
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This group of species has very little lateral deviation along the orbital axis
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Carnivore
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This group of species has a wide lateral deviation of the orbital axis.
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Herbivores
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What is the trade-off associated with having a wide deviation of the orbital axis (as seen in herbivores)?
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Poor binocular vision
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These structures pass through the orbital fissure
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CN III, CN IV, ophthalmic branch of CN V, CN VI
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These structures pass through the optic foramen
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CN II
Internal ophthalmic artery |
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These structures pass though the round foramen.
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Maxillary artery and vein
Maxillary nerve (branch of CN V) |
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These species have a foramen orbitorotundum.
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Cattle
Sheep Pigs |
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The frontal nerve passes through this foramen in the horse and some cattle to innervate the nasal half of the upper eyelid.
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Supraorbital foramen
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Primary blood supply to the globe comes from the...
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External ophthalmic artery and its branches
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One eye or a fused pair of eyes in the central area of the forehead.
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Cyclopia
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This plant, when consumed by pregnant ewes on the 14th day of gestation, will cause cyclopia.
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Veratrum californicum
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Underdeveloped, non-functional eyeball
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Microphthalmia
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Small but functional eye
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Nanophthalmia
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Species usually affected by cyclopia.
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Sheep and goats
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In which species is mircophthalmia an inherited trait? Cats or dogs?
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Dogs
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These breeds are predisposed to having microphthalmia.
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Dobermans, Saint Bernards, Beagles, Shetland Sheepdogs, Collies, Miniature Schnauzers, Merle Australian Shepherds
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The gene causing microphthalmia is often associated with this gene
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Color dilute gene
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Deficiency of this nutrient during gestation may cause microphthalmia in pigs.
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Vitamin A
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Proper term for the form of "crossed eyes" seen in SIamese cats.
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Convergent strabismus
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Divergent strabismus is commonly seen in this group of dog breeds.
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Brachycephalics
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THis disorder is associated with 100% decussation of the optic nerve fibers at the optic chiasm as well as abnormal nerve fibers from the lateral geniculate nucleus to the optic cortex in the brain.
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Convergent strabismus
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Convergent strabismus is a recessive, inherited trait in these cow breeds.
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Jersey, Shorthorn, Holstein
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How do canine retrobulbar abcesses typically present: acute or chronic?
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Acute
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A dog presents with acute pyrexia, chemosis, and protrusion of the bulbar conjunctiva and third eyelid, pain on opening the mouth, and a fluctuant red swelling in the back of the oral mucosa on the same side. What is a likely differential diagnosis?
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Retrobulbar abcess
(also r/o orbital cellulitis and retrobulbar neoplasia) |
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How are retrobulbar abcesses typically caused in the dog?
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Penetrating wounds through floor of orbit thru pterygoideus muscle
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How are retrobulbar abcesses in dogs treated typically?
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Drainage of abcess through incision behind the last molar.
Systemic abx NSAIDs Warm compresses +/- temporary tarsorraphy |
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How frequently do retrobulbar abcesses occur in cats?
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Not frequently
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Common cause of retrobulbar abcess in guinea pigs and chinchilas
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Manipulations of the teeth and Actinomyces contamination of the orbit
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Typical cause of orbital cellulitis in the dog
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Secondary to external injury like migrating parasitic larvae, frontal sinus disease, septicemias, fractures of orbital bones with secondary bony sequestra, diseased teeth
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Clinical signs associated with orbital cellulitis in the dog.
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Febrile possibly
Waxing and waning disease Chemosis of conjunctiva with firm swelling around the orbit Pain on opening of mouth |
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How is orbital cellulitis diagnosed?
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Radiography/CT scan
Blood culture FNA and cytology/culture Attempt to drain retrobulbar abcess Exploratory orbitotomy |
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How is obital cellulitis treated?
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ID cause and treat accordingly
(Drainage, antibiotics, removal of sequestrum, etc.) |
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Causes of orbital cellulitis in the horse
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Puncture wounds
Blunt trauma Sinus diseases Neoplasia |
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In which species is eosinophilic myositis complex, or masticatory myositis, typically seen?
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Dogs
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Breeds predisposed to masticatory myositis.
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German shepherds
Golden Retrievers Labrador Retrievers Weinmaraners |
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The acute form of this disease presents with bilateral, symmetrical exophthalmia.
May also see conjunctival hyperremia and chemosis, 3rd eyelid proptosis, and pain on palpation of the head. Opening the mouth is quite painful. |
Eosinophilic myositis complex
aka. masticatory myositis |
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The chronic form of this disease is marked by atrophy and fibrosis of the masticatory muscles, enophthalmos, and possibly an inability to open the mouth.
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Eosinophilic myositis complex
aka. masticatory myositis |
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How is eosinophilic myositis complex diagnosed?
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Increased CK and SGOT
Muscle biopsy demonstrating muscle necrosis and eosinophils 2M myofibril serologic test |
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How is eosinophilic myositis complex treated?
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Immunosuppressive doses of steroids followed by weaning and long term therapy with steroids.
Severe cases may use azathioprine |
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How is enophthalmia treated surgically?
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Surgical removal of part of the 3rd eyelid
Restoration of the retrobulbar mass with implants |
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In what signalment is extraocular myositis typically seen?
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Young large breed dogs like Labs, Golden retrievers, Dobermans, and other field breeds
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A Labrador retriever presents with bilateral exophthalmia that is non-painful. On retropulsion there is a doughy feeling.
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Extraocular myositis
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What causes vision deficit in severe extraocular myositis?
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Impingement on optic nerve from extraocular muscle swelling
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How is extraocular myositis treated?
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Immunosuppressive doses of corticosteroids
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In which disease is recurrence more likely: Extraocular myositis, or masticatory myositis?
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Masticatory myositis
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In which species are orbital neoplasias more commonly seen?
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Dogs
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Orbital neoplasia carries this prognosis
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Guarded to poor
(Locally invasive, poor response to treatment, malignant, typically nonexcisable by the time of presentation) |
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Clinical signs seen with orbital neoplasia include
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Exophthalmos (rarely enophthalmos)
Slowly progressive Unilateral Non-painful +/- blindness |
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Typical therapy for orbital tumors
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Excision (exteneration of orbit +/- orbitotomy)
Radiation therapy Chemotherapy Cryosurgery |
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Most common orbital neoplasia seen in catle
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Lymphosarcoma
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Prognosis for ocular lymphosarcoma in cattle
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Very poor-- systemic
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Prognosis for third eyelid neoplasia in the dog
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Fairly good-- excision may be curative!
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Most commonly seen in small animals due to incomplete orbit. May be caused by opening mouth widely for intubation.
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Proptosis of the globe
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Most common cause of globe proptosis in the dog and cat
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Trauma
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Why is a traumatic globe proptosis in a large animal so much more serious than in a small animal?
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Extensive injury must be caused in order to dislodge the globe from a complete orbit
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Prognosis of globe proptosis in cats
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Poor
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Prognosis of globe proptosis in dogs is the most serious in these breeds.
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Enophthalmic breeds like Collies and Schnauzers
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How is a proptosed globe treated?
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FIRST keep cornea moist with tears, ointment, or Vaseline
Examine animal for other fractures (head, neck, spine, etc) Replace eye into orbit with lateral canthotomy +/- tarsorraphy or 3rd eyelid flap (left 1-2 weeks) Systemic abx and possibly steroids. |
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Complications seen when a proptosed globe is replaced
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Retrobulbar hemorrhage and poor seating of the globe due to inflammation
Avulsion of extraocular muscles or optic nerve |
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List some prognositc indicators seen with a proptosed globe
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Time (the longer, the worse)
Corneal/scleral integrity (enucleate if lacerated) Pupilary reaction (miotic is normal, fixed and dilated is bad) Hyphemia indicates further deep ocular disease |
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What should be done with a proptosed globe if its future is questionable?
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Replace into orbit and suture shut. It can always be removed later
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Normal pupillary response to trauma
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Miosis
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True or false: True enucleations are seldom done in veterinary medicine.
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True
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Removal of the globe, leaving the orbital tissue and extraorbital muscles intact as well as the eyelids.
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Enucleation
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Most "enucleations" in veterinary medicine combine these two procedures
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Enucleation and exteneration (removal of globe, conjunctival tissue, third eyelid, lid margins, lacrimal gland, other secretory tissues)
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Removal of the entire orbital contents, including glandular structures, muscles, nerves, parts of the eyelids, and all other tissues within the orbit
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Exteneration
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Most common signalment in which globe evisceration and implantation is used.
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Show horses
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