Week 1 Anatomy and Disease of Orbit Study Questions Flashcards
(25 cards)
What species have complete bony orbits
cow, horse, pig, primates
What species have incomplete bony orbits, and what compromises the rim of the orbit in these species
carnivores (dogs & cats) - orbital ligament
what is the innervation, origin, insertion and action on the globe of Ventral Rectus
CN III (oculomotor)
-inserts into sclera near or slightly anterior to the equator of the globe
-functions to rotate globe vertically acting antagonistically with the dorsal rectus
what is the innervation, origin, insertion and action on the globe of Lateral Rectus
CN VI (abducent)
-inserts into sclera near or slightly anterior to the equator of the globe
-functions to rotate globe horizontally acting antagonistically with the medial rectus
what is the innervation, origin, insertion and action on the globe of Dorsal Oblique
CN IV (trochlear)
-originates near optic foramen, passes through trochela along the medial orbital wall to insert into the sclera laterally near insertion of lateral rectus muscle
-functions to provide intorsion (rotate dorsal globe medially)
what is the innervation, origin, insertion and action on the globe of Ventral Oblique
CN III (oculomotor)
-originates from the medial orbital wall
-inserts by muscular insertion!! deep to the lateral rectus insertion
-provides extorsion (rotates dorsal globe laterally)
what is the innervation, origin, insertion and action on the globe of Retractor Bulbi
CN VI (abducent)
- originates within orbital fissure
- inserts into posterior sclera of the globe
- retracts the globe, well developed in herbivores
what is the innervation, origin, insertion and action on the globe of Levator Palpebral Superioris
CN III (oculomotor)
- originates near dorsal rectus next to orbital fissure
- inserts in a broad band to upper tarsus
- elevates lateral 2/3 of upper eyelid, intimate connection to dorsal rectus
what is buphthalmos and what causes it
globe enlargement (ex glaucoma)
what is exophthalmos and what causes it
increased protrusion of the globe
causes:
-neoplasia
-hemorrhage
-cellulitis/abscess
-mucocele
-myositis
why is oral examination important when evaluating orbital disease?
swelling/fistulas in the mouth, oral pain can narrow differentials
what is enophthalmos and what causes it
retraction of globe into orbit
causes:
-dehydration
-cachexia
-increased extraocular muscle tone
-atrophy of orbital fat
-loss of periorbita (neoplasia in cats)
-loss of retro-orbtial muscle mass
unilateral enophthalmos is caused by
neoplasia, atrophy of orbital fat
bilateral enophthalmos is caused by
a systemic condition- dehydration, cachexia
what is microophthalmos
congenitally small globe +/- vision
what is phthisis bulbi
shrunken globe without vision associated with chronic intraocular disease
what are the possible initiating causes of orbital cellulitis/abscess
extension into orbit from adjacent periorbital infection (tooth root abscess, sinus infection) or migrating plant foreign body
Cellulitis differentials
common in dog, not in cat
unilateral presentation with non-painful 3rd eyelid prolapse
acute onset
pain on opening of mouth
pyrexia & leukocytosis
swelling/fistula in roof of mouth behind last upper molar
neoplasia differentials
middle-aged to older animals
unilateral
gradual onset
slow progression
what is the difference between primary and secondary orbital neoplasia
primary originates in orbit
secondary has metastasis/extension from continguous structures
what is the species breakdown between primary and secondary orbital neoplasia
dog - 90% malignant, 75% primary
cat- 90% malignant, 15% primary (MOSTLY SECONDARY!)
Horse- malignant, secondary (SCC!)
what breeds of dogs are predisposed to orbital proptosis
PEKINGESE! or any brachycephalic with shallow orbits
how are proptosis treated?
enucleation or replace
what are the common complications associated with proptosis?
corneal ulcer - no corticosteroids!
KCS sicca
lateral strabismus
blindness
