Ophthalmology - Exam and Orbit Flashcards
What are the afferent and efferent components of the palpebral reflex?
CN V - afferent
CN VII - efferent
What are the afferent and efferent components of the menace response?
CN II - afferent
CN VII - efferent
What are the afferent and efferent components of the pupillary light reflex?
CN II - afferent
CN III - efferent
What are the afferent and efferent components of the dazzle reflex?
CN II - afferent
CN VII - effernet
What is the afferent component of the corneal reflex?
CN V
When is the Shirmer tear test performed?
- before any other drops or ointments
- before sedation or anesthesia
How is the Shirmer tear test performed?
- test strip is placed laterally in the conjuctival sac
- close the eyes and leave the strip in for 60 seconds
- measuring tear production
What is the normal value for the Shirmer tear test?
- unpredictable in cats
- dogs: > 15mm/minute
What is Fluorescein stain?
hydrophilic dye that fluoresces green under cobalt blue light
When is a Fluorescein stain done?
- diagnosis and characterization of corneal ulceration
- demonstration of nasolacrimal patency
- demonstration of corneal perforation
What does tonometry measure, and how are the results interpreted?
- measures intraocular pressure
- the lowest reading is the most accurate
What is the normal intraocular pressure measurement?
10-20 mmHg
< 8 mmHg difference between eyes
Describe the the features of direct ophthalmoscopy in respect to indirect
Direct: - higher magnification - lower field of view - lower depth perception - easier to use - less safe Indirect: image is reversed and upside-down
What are the abbreviations for right, left, and both eyes?
OD - right eye
OS - left eye
OU - both eyes
What is retropulsion?
applying light pressure to both eyes through the lids to detect for asymmetry
What is specular reflection?
the mirror-like reflection of light form the surface of the eye
Which tooth is commonly involved in orbital/periorbital disease?
the carnassial tooth
4th premolar
Which nerves pass through the orbital fissure?
CN III, IV, V, VI
What is exophthalmos?
abnormal protrusion of the eye from the orbit
What are the clinical signs associated with exophthalmos?
- third eyelid protrusion
- facial swelling
- soft palate bulging
- pain on opening mouth
- fever
What are possible causes of exophthalmos?
- orbital volume imbalance
- orbital neoplasia
- orbital cellulitis/abscess
- zygomatic salivary gland mucocele
- masticatory muscle myositis
- extraocular myositis
- retrobulbar hemorrhage
What are the treatment options for orbital neoplasia?
globe-sparing - radiation - surgical exploration - chemotherapy globe removal - enucleation - exenteration
What are the treatment options for orbital cellulitis/abscess?
- anti-inflammatory therapy and antibiotics
- surgical exploration and/or drainage
What is enophthalmos?
abnormal recession of the eye within the orbit
What are the clinical signs associated with enophthalmos?
- facial muscular loss
- third eyelid protrusion
- entropion
What are the possible causes of enophthalmos?
orbital volume imbalances: - dehydration, emaciation - myopathies, space occupying lesions anterior to globe active globe retraction: - skeletal muscle - ocular pain passive globe retraction: - smooth muscles - Horner's syndrome
What is microphthalmos?
a congenitally small globe
What is phthisis bulbi?
an acquired shrunken globe, most often from severe or chronic inflammation
What is strabismus?
deviation of one or both eyes, so that both eyes are not directed at the same object
What are the possible causes of strabismus?
congenital: - brachycephalics and siamese cats - hydrocephalus acquired: - dysfunction of any rectus muscle - imbalance of orbital volume
What is proptosis?
anterior displacement of the globe such that the eyelids are caught behind the equator of the globe
What are positive prognostic factors for proptosis?
- brachycephalics
- < 3 extraocular muscles torn
- positive direct and indirect PLRs
What are negative prognostic factors for proptosis?
- cats and doliochocephalics
- > 3 extraocular muscles torn
- ruptured eye
- hyphema
- orbital fractures
What is the vision prognosis for proptosis?
75-80% will be blind
How is proptosis treated?
- lubricate the cornea
- replacement: horizontal mattress sutures, push eye down with flat edge and pull sutures up, temporary tarsorrhaphy
What are the possible complications that can result from proptosis replacement?
- corneal ulceration
- loosening of sutures
- strabismus
- KCS
- blindness
- repeated proptosis
- need for enculeation
Describe the anatomic features of the orbit in brachycephalic dogs
- orbital ligament spans a greater portion of the orbital rim
- orbit is much shallower
- more susceptible to ocular disease
What is the periorbital cone?
supportive cone-like structure that contains the eyeball, extraocular muscles, fat, vessels, nerves, and fascia, that reside within the orbit
What is the orbital ligament?
ligamentous structure that forms the lateral boundary of the boney orbit in cats and dogs
What is buphthalmos?
abnormal enlargement of the eyeball
What is Horner’s Syndrome?
sympathetic denervation to the eye and ocular adnexa
