Conditions of the globe and orbit Flashcards
list 6 intraconal structures (or groups of structures)
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
list 4 extraconal structures (or groups of structures)
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
define the intraconal space
space within the muscle cone formed by the extraocular muscles
define the extraconal space
space outside the muscle cone but within the orbit
give 4 clinical characteristics of intraconal orbital disease
axial exophthalmos
absence or minimal protrusion of TEL
absence or minimal strabismus
limited ocular motility in some instances
give 4 clinical characteristics of extraconal orbital disease
non-axial exophthalmos
globe deviation
protrusion of TEL
retention of ocular motility
what frequency ultrasound probe is recommended for orbital detail?
7.5-10MHz
what is the difference between microphthalmos and nanophthalmos?
Microphthalmos - a small globe with abnormalities
Nanophthalmos - a small globe without abnormalities
Give 4 breeds that have been shown to have inherited microphthalmos and give the concurrent defects usually seen with it in each breed
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)
true or false: blunt ocular trauma has a worse visual prognosis that penetrating trauma
true
which muscles are affected in masticatory muscle myositis?
muscles derived from the 1st brachial arch, innervated by the mandibular branch of CN V and containing 2M myofibers
(masseter, temporal, pterygoid)
what are the clinical signs for acute MMM?
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
what are the clinical signs of chronic MMM?
fibrosis or atrophy of the masticatory muscles leading to enophthalmos with secondary entropion
trismus (can sometimes be seen in acute stage too)
what clinical and labratory information is useful in the diagnosis of MMM?
clinical signs raised CK neutrophilia type 2M myofibril antibodies biopsy of temporalis muscle electromyography
how is MMM treated?
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)
what is the typical signalment for a dog with bilateral extraocular myositis?
young, entire female dogs
golden retreivers
what are the clinical signs of BEP?
bilateral intraconal disease: bilateral exophthalmos no TEL protrusion 360 degree scleral show retraction of upper eyelids reduction in oculovestibular movements
what is the proper name for FROMS?
feline restrictive myofibroblastic sarcoma
why do doli/meso cephalic breeds and non-brachycephalic cats have a poor prognosis in regards to proptosis?
more severe trauma is required to proptose the eye
The orbital fissure and optic canal form the caudal part of the orbit. In which bone are they found?
Sphenoid bone
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
Cranial nerve V (trigeminal) - ophthalmic branch
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
Patients will have reduced to absent physiological nystagmus (reduced oculovestibular movements)
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
Absence of any extraocular muscle avulsion or rupture
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
Malignant, highly locally invasive and with a low metastatic rate
what are the most commonly reported primary orbital tumours in the dog?
osteosarcoma, fibrosarcoma, undifferentiated sarcomas, adenocarcinoma and meningioma
