Week 1 Anatomy and Disease of Orbit Study Questions

Question 1

What species have complete bony orbits

Answer 1

cow, horse, pig, primates

Question 2

What species have incomplete bony orbits, and what compromises the rim of the orbit in these species

Answer 2

carnivores (dogs & cats) - orbital ligament

Question 3

what is the innervation, origin, insertion and action on the globe of Ventral Rectus

Answer 3

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

Question 4

what is the innervation, origin, insertion and action on the globe of Lateral Rectus

Answer 4

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

Question 5

what is the innervation, origin, insertion and action on the globe of Dorsal Oblique

Answer 5

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)

Question 6

what is the innervation, origin, insertion and action on the globe of Ventral Oblique

Answer 6

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)

Question 7

what is the innervation, origin, insertion and action on the globe of Retractor Bulbi

Answer 7

CN VI (abducent)
- originates within orbital fissure
- inserts into posterior sclera of the globe
- retracts the globe, well developed in herbivores

Question 8

what is the innervation, origin, insertion and action on the globe of Levator Palpebral Superioris

Answer 8

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

Question 9

what is buphthalmos and what causes it

Answer 9

globe enlargement (ex glaucoma)

Question 10

what is exophthalmos and what causes it

Answer 10

increased protrusion of the globe

causes:
-neoplasia
-hemorrhage
-cellulitis/abscess
-mucocele
-myositis

Question 11

why is oral examination important when evaluating orbital disease?

Answer 11

swelling/fistulas in the mouth, oral pain can narrow differentials

Question 12

what is enophthalmos and what causes it

Answer 12

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

Question 13

unilateral enophthalmos is caused by

Answer 13

neoplasia, atrophy of orbital fat

Question 14

bilateral enophthalmos is caused by

Answer 14

a systemic condition- dehydration, cachexia

Question 15

what is microophthalmos

Answer 15

congenitally small globe +/- vision

Question 16

what is phthisis bulbi

Answer 16

shrunken globe without vision associated with chronic intraocular disease

Question 17

what are the possible initiating causes of orbital cellulitis/abscess

Answer 17

extension into orbit from adjacent periorbital infection (tooth root abscess, sinus infection) or migrating plant foreign body

Question 18

Cellulitis differentials

Answer 18

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

Question 19

neoplasia differentials

Answer 19

middle-aged to older animals
unilateral
gradual onset
slow progression

Question 20

what is the difference between primary and secondary orbital neoplasia

Answer 20

primary originates in orbit
secondary has metastasis/extension from continguous structures

Question 21

what is the species breakdown between primary and secondary orbital neoplasia

Answer 21

dog - 90% malignant, 75% primary
cat- 90% malignant, 15% primary (MOSTLY SECONDARY!)
Horse- malignant, secondary (SCC!)

Question 22

what breeds of dogs are predisposed to orbital proptosis

Answer 22

PEKINGESE! or any brachycephalic with shallow orbits

Question 23

how are proptosis treated?

Answer 23

enucleation or replace

Question 24

what are the common complications associated with proptosis?

Answer 24

corneal ulcer - no corticosteroids!
KCS sicca
lateral strabismus
blindness

Question 25

what are the principles of treating proptosis

Answer 25

you can always take it out but you cant put it back

always lube globe before stabilizing patient