Orbital Diseases Flashcards
(36 cards)
What is the normal canine and feline orbit like?
incomplete - orbital ligament completes it laterally and the floor is left open
- made up of bone, fat, muscle, nerves, blood vessels, and glands (salivary, lacrimal)
What other structures are close to the orbit in all domestic species?
- mouth
- nasal cavity
- ramus of mandible
- sinuses
all possible origins of disease
Orbit structures:
What does orbital position depend on?
visual fields
- horses = monocular, laterally placed orbits
- dogs, primates = binocular, more medial orbits
What is enophthalmos? What are 5 common causes?
sinking in of the globe
- ocular pain - retraction
- Horner’s syndrome - lack of sympathetic tone
- loss of orbital fat
- phthisis bulbi, microphthalmia
- end-stage extraocular muscle myositis or atrophy following severe cellulitis
What is exophthalmos? What are some causes?
protruding globe
- neoplasia
- abscess/cellulitis
- FB
- masticatory or extraocular muscle myositis
- salivary mucocele
- sialoadenitis
- trauma
- cysts
- vascular anomalies
What are the 3 origins of exophthalmos?
- intraconal - swelling within cone of muscles
- extraconal
- within the orbit, outside periorbita
How does intraconal exophthalmos present? What are the 2 major etiologies?
projection of the globe forward without elevation of the third eyelid
- extraocular muscle myositis - always bilateral, must be differentiated from more common abscesses
- optic nerve meningiomas
How does extraconal exophthalmos present? What are the 2 most common etiologies?
elevation of third eyelid and deviation of the globe (strabismus) depending on mass location —> most common!
- retrobulbar abscess/cellulitis
- orbital neoplasia
What are the 2 most common etiologies of orbital exophthalmos?
- masticatory muscle myositis
- zygomatic sialoadenitis/mucocele
(no bony wall = orbit issues)
What are 2 examples of nearby structures that can cause exophthalmos?
- tooth root infections (carnassials!)
- neoplasia migrated from nasal cavity, ear, mouth, or sinus (nasal adenocarcinoma)
Why is examining the orbit especially difficult? What needs to be assessed?
cannot see it - observe from above!
- eye/periorbita
- head and eye position
- eyelid closure
- third eye location
- symmetry
What is the most important aspect of examining the orbit? What else is also commonly done?
retropulse the globes
- perform vision tests, like a menace response, maze, and tracking
- perform tonometry*, Schirmer tear test, and fluorescein stain
- open mouth to assess pressure the ramus of the mandible is putting on the globe —> abscesses are much more painful!
What does orbital disease commonly look like? How can it be differentiated?
conjunctivitis
- third eyelid position
- retropulsion of the globe
How does orbital disease affect vision and intraocular pressure?
vision should be normal, there can rarely be some retinal detachment —-> meningioma can affect vision!
usually normal to slightly elevated
What does pain upon closure of the mouth indicate for orbital disease? What is commonly seen?
- abscess
- cellulitis
- FB
swollen/red behind last molar (may need anesthesia to observe)
What is the classive examination finding indicative of orbital neoplasia?
exophthalmos with very little to no pain on opening of the mouth
- check for epistaxis, air flow from nostril, and pain around the eye
How does orbital neoplasia typically progress? What change in the posterior eye may be seen? Pupil?
slowly progressive (abscesses would be much more acute)
deviation of the retina due to pressure from mass behind the globe
normal to dilated
What are the most common type of tumors of the orbit in small animals?
90% are malignant (HSA, lymphoma) and very invasive to surrounding structures
What are the most common types of neoplasias seen in the orbits of dogs and cats? What others are also seen?
- DOGS = adenocarcinoma
- CATS = SCC
lymphoma, osteosarcoma, fibrosarcoma, chondrosarcoma, meningioma, mast cell tumors
Exophthalmos characteristics:
Is radiography commonly used for diagnosing orbital disease? What are MRI and CT usually used for?
no —> large amounts of soft tissue surrounding
MRI - optic nerve disease, tumors, soft tissues
CT - soft tissue, tumors, bony involvement
What is ocular ultrasound most commonly used for in diagnosing orbital disease? What is its major downfall?
- differentiate abscesses, cellulitis, and tumors
- guidance for aspirates and biopsies
will not show the borders of tumors
Why is it difficult to diagnose orbital neoplasia with ultrasound? What are 3 possible findings?
orbital bone interferes
- blunting of globe
- inability to delineate optic nerve
- discrete mass in space
