Conditions of the globe and orbit

Question 1

list 6 intraconal structures (or groups of structures)

Answer 1

extraocular muscles
cranial nerves (II, III, IV, VI, V ophthalmic)
orbital lacrimal gland
orbital fat
autonomic nerves, arteries and veins
smooth muscle enveloping the periorbita

Question 2

list 4 extraconal structures (or groups of structures)

Answer 2

zygomatic salivary gland
base of nictitating membrane
neurovascular structures traversing the orbital floor (maxillary artery, palatine nerve, intraorbital nerve, maxillary branch of trigeminal nerve, parasympathetic pterygopalatine nerve and ganglion
orbital fat cushion

Question 3

define the intraconal space

Answer 3

space within the muscle cone formed by the extraocular muscles

Question 4

define the extraconal space

Answer 4

space outside the muscle cone but within the orbit

Question 5

give 4 clinical characteristics of intraconal orbital disease

Answer 5

axial exophthalmos
absence or minimal protrusion of TEL
absence or minimal strabismus
limited ocular motility in some instances

Question 6

give 4 clinical characteristics of extraconal orbital disease

Answer 6

non-axial exophthalmos
globe deviation
protrusion of TEL
retention of ocular motility

Question 7

what frequency ultrasound probe is recommended for orbital detail?

Answer 7

7.5-10MHz

Question 8

what is the difference between microphthalmos and nanophthalmos?

Answer 8

Microphthalmos - a small globe with abnormalities

Nanophthalmos - a small globe without abnormalities

Question 9

Give 4 breeds that have been shown to have inherited microphthalmos and give the concurrent defects usually seen with it in each breed

Answer 9

doberman: anterior segment dysgenesis and retinal dysplasia
miniature schnauzer - cataracts, microphakia, posterior lenticonus, nystagmus, retinal dysplasia
cavalier king charles spaniel - cataracts, nystagmus, posterior lenticonus, persistant hyaloid artery
australian shepherd - equatorial staphyloma, persistent pupillary membranes, iris colobomes, retinal dysplasia. (linked to merle gene)

Question 10

true or false: blunt ocular trauma has a worse visual prognosis that penetrating trauma

Answer 10

true

Question 11

which muscles are affected in masticatory muscle myositis?

Answer 11

muscles derived from the 1st brachial arch, innervated by the mandibular branch of CN V and containing 2M myofibers
(masseter, temporal, pterygoid)

Question 12

what are the clinical signs for acute MMM?

Answer 12

swelling of the temporalis muscle which leads to signs of extraconal disease: exophthalmos and protrusion of the nictitating membrane.
Generalized signs include pyrexia and anorexia.
Patients show signs of pain when attempting opening the mouth or on palpation of the masticatory muscles

Question 13

what are the clinical signs of chronic MMM?

Answer 13

fibrosis or atrophy of the masticatory muscles leading to enophthalmos with secondary entropion
trismus (can sometimes be seen in acute stage too)

Question 14

what clinical and labratory information is useful in the diagnosis of MMM?

Answer 14

clinical signs
raised CK 
neutrophilia
type 2M myofibril antibodies
biopsy of temporalis muscle
electromyography

Question 15

how is MMM treated?

Answer 15

immunosuppressive dose of pred, maintained until resolution of clinical signs then slowly taper whilst monitoring for recurrence. 
Azathioprine is another option for long term
symptomatic care (physio for jaw motility etc)

Question 16

what is the typical signalment for a dog with bilateral extraocular myositis?

Answer 16

young, entire female dogs

golden retreivers

Question 17

what are the clinical signs of BEP?

Answer 17

bilateral intraconal disease:
bilateral exophthalmos
no TEL protrusion
360 degree scleral show
retraction of upper eyelids
reduction in oculovestibular movements

Question 18

what is the proper name for FROMS?

Answer 18

feline restrictive myofibroblastic sarcoma

Question 19

why do doli/meso cephalic breeds and non-brachycephalic cats have a poor prognosis in regards to proptosis?

Answer 19

more severe trauma is required to proptose the eye

Question 20

The orbital fissure and optic canal form the caudal part of the orbit. In which bone are they found?

Answer 20

Sphenoid bone

Question 21

Which one of the following structures is located within the orbital cone (ie is an intraconal structure)?

a. Cranial nerve V (trigeminal) - ophthalmic branch
b. Maxillary artery
c. Base of the nictitans membrane
d. Zygomatic salivary gland

Answer 21

Cranial nerve V (trigeminal) - ophthalmic branch

Question 22

Regarding the condition ‘bilateral extraocular myositis’, which is the most accurate statement?

a. Patients will have reduced to absent physiological nystagmus (reduced oculovestibular movements)
b. Patients will have elevated 2M antibodies
c. Treatment consists of oral NSAIDs until clinical signs resolve
d. This type of myositis is most commonly seen in elderly male dogs

Answer 22

Patients will have reduced to absent physiological nystagmus (reduced oculovestibular movements)

Question 23

Which of the following prognostic factors is a good indicator of the viability of the globe in a patient with proptosis?

a. Non-brachycepahlic conformation
b. Absence of any extraocular muscle avulsion or rupture
c. Presence of a menace response and dazzle reflex
d. The pupil size - if miotic it is likely that the globe will be functional

Answer 23

Absence of any extraocular muscle avulsion or rupture

Question 24

Primary orbital tumours in small animal patients tend to be

a. Malignant, with low local invasiveness and a low metastatic rate
b. Benign and surgical excision tends to be curative
c. Malignant, with low local invasiveness but a high metastatic rate
d. Malignant, highly locally invasive and with a low metastatic rate

Answer 24

Malignant, highly locally invasive and with a low metastatic rate

Question 25

what are the most commonly reported primary orbital tumours in the dog?

Answer 25

osteosarcoma, fibrosarcoma, undifferentiated sarcomas, adenocarcinoma and meningioma