Opthomology Flashcards
OD
right eye
OS
left eye
OU
both eyes
photopic
in well lit environment
scotopic
in a dark environment
retroillumination
using light that is shone into the eye to reflect against internal structures and highligt normal/abnormal features during the ophthalmic exam
retropulsion
applying light pressure to both eyes (through the eyelids) simultaneously with your index finger to detect for asymmetry.
This is useful for decrecting dz of the orbit or space occupying lesion behind the globe
corneal ulcerstion
disruption of the corneal epithelium & exposure of the corneal stroma
positive Jones test
application of fluorescein dye to the ocular surface which then appears at the nares.
This is a test of nasolacrimal patency
positive Seidel test
application of fluorescein dye to the ocular surface and subsequent appearance of aqueous humor leaking through dense fluorescein stain.
This test confirms corneal perforation
Specular reflection
the mirror-like reflection of light from the surface of the eye
Can be used to assess the health of the ocular surface
This reflection becomes disturbed when the surface is irregular
what is the gold standard for discerning depth when examing eye
slit lamp biomicroscope
- requires a focused, narrow, bright, beam of light
what are the 3 types of vision tests
cotton ball test
photopic maze
scotopic maze
what do the menace response, PLR & dazzle reflex specfically identify?
the function of cranial nerves that also help assess for presence of vision
what are the tests of orbital symmetry
orbital palpation
dorsal view assessment
retropulsion
what doest retroillumination do
help visualize the deepest structures of the eye
what are the 6 cranial nerve assessments
palpebral reflex
menac response
PLR
dazzle reflex
oculocephalic reflex
corneal reflex
what nerves does the palpebral reflex check
CN V (afferent)
CN VII (efferent)
What nerves doe the menace response check
CN II (afferent)
CN VII (efferent)
What nerves does the pupillary light reflex (PLR) check
CN II (afferent)
CN III (efferent)
What nerves does the dazzle reflex check
CN II (afferent)
CN VII (efferent)
What nerves does the oculocephalic reflex check
Intact CN II*, peripheral & central vestibular components, CN III, IV & VI
*CN II does not need tofunction in order to elicit a positive oculocephalic reflex, though it is necessary to develop the reflex initially
What nerves does the corneal reflex check
CN V (afferent)
CN VI & VII (efferent)
What is considered the minimum database of testing for ocular disorders
STT
Fluorescein stain
Tonomety
how does fluorescein stain help with the dx & characterization of corneal ulceration
Jones test
Seidel test
what are the 2 types of tonometry
applanation
rebound
what does the Schirmer tear test do
assesses the aqueous portion of the tear film
- 60 second test time
normal:
Dogs = >15mm wetting/minute
- basal & reflex tearing
Cats = unpredictable-
what if fluorescein stain and how does it work
Hydrophilic dye that fluoresces green under cobalt blue light
Tear fluid - hydrophillic - will stain & needs to be flushed
Epithelium - hydrophobic - will not stain
Stroma - hydrophilic - will stain bright green
Descemet’s membrane - hydrophobic - will not stain
how is a corneal ulceration dx’d by fluorescein
if the corneal stroma is exposed by ulceration there will be uptake by stroma of fluorescein stain
what does the Jones test assess
nasolacrimal patency
- patent lacrimal ducts will allow flow of fluoroscein dye from upper & lower punctum > lacrimal sac > nasolacrimal duct > nasal & pharyngeal openings
will see green coming from nares
- blockag of this system could cause epiphora
What does a postive Seidel test confirm
corneal perforation
demonstrats aqueous leakin through fluorescein stain
what are the 2 types of tonometry
applanation & rebound
what do tonometers measure
intraocular pressure in mmHg
How is intraocular pressure interpreted
10-20 mmHg normal
should be < 25mmHg at all times
what would high or low IOP indicate
>25mmHg w/ vision loss = Glaucoma
Low IOP consistent w/ Uveitis
What is commonly seen in Bovine SCC
blepharitis
How can you tell if the cornea is damaged
specular reflection
How does specular reflection assist in lesion localization
disturbance of the reflection indicates irregularity of the ocular surface
bony orbit
A part of the adenexa, the conical bony structure that contains the eyeball and periobital cone
periobital cone
Supportive cone like structure that contains the eyeball, extraocular muscles, fat, vessels, nerves, and fascia that reside within the orbit
orbital ligament
Ligamentous structured that forms the lateral boundary of the bony orbit in cats and dogs
exophthalmos
Abnormal protrusion of the eye from the orbit. The position is abnormal. The globe size is normal.
Buphthalmos
Literally means “cows eye” that refers to the abnormal enlargement of the eyeball. For practical purposes, buphthalmos is only caused by glaucoma. The sizes is abnormal, the position is normal.
enophthalmos
Abnormal recession of the eye within the orbit
strabismus
Deviation of one or both eyes, so that both eyes are not directed at the same object
Horner’s syndrome
Sympathetic denervation to the eye and ocular adnexa. There are four classic clinical signs:
enophthalmos
Ptosis - drooping of eyelid
Miosis
Protrusion of the third eyelid
microphthalmos
A congenitally small and malformed globe
phthisis bulbi
Acquired shrunken globe, most often from severe or chronic inflammation
Proptosis
Anterior displacement of the globe such that the eyelids are caught behind the equator of the globe
what do these skulls show
Species and breed differences in bony orbit structure
What makes cat and dog orbits special
They have open orbits
The have an orbital ligament which forms the lateral boundary of the orbital rim
much shorter in cats giving their orbit more bony protection relative to the dog
What are two features of brachycephalic dog skulls that are different th dolichocephalic skulls that make them are very susceptible to ocular disease
Orbital ligament Spans a greater portion of the orbital rim
Orbit is much shallower
What are three disorders of globe position
exophthalmos
enophthalmos
strabismus
What are three disorders of globe size
buphthalmos
phthisis bulbi
microphthalmos
What are commonly associated clinical signs with exophthalmos
Third eyelid protrusion
Facial swelling
Soft palate bulging
Pain opening mouth
Fever
What is the single most common mechanism of exophthalmos
Orbital volume imbalance
What are the two most common conditions that cause exophthalmos
Orbital neoplasia - often malignant, slowly progressive, often non-painful
Orbital cellulitis/abscess - working dogs and stick chewers, acute onset, often painful
when would exophthalmos be considered “normal”
In brachycephalic breeds
What is this an example of
exophthalmos & lateral strabismus
What is this an example of
buphthalmos
d/t glaucoma 2o to uveitis
what is exophthalmos dx approach
Complete general and ophthalmic examination
tests of orbital symmetry
Oral examination
Complete blood count, Serum Chemistry
+/-Chest radiographs
Advanced imaging (CT and/or MRI)
Tissue sampling
Fine needle aspiration
Biopsy
orbital neoplasia tx options
enucleation - removal of eye
exenteration - removal of the eye & all orbital contents
orbital cellulitis/abscess 2 tx approaches
medical
sx
common CS w/ enophthalmos
facial mm loss (unilat or bilat)
3rd eyelid protrusion
entropion
3 common mechanisms for enophthalmos
orbital volume imbalance
active globe retraction
passive globe retraction
common causes of enophthalmos
dehydration
emaciation or cachexia
myopathies
spce occupying lesions anterior to the globe
Ocular pain
horner’s syndrome
don’t confuse enophthalmos with these 2 disorders of globe size
microphthalmos
phthisis bulbi
what are congenital & acquired causes of strabismus
congenital:
normal variation (think pug heads)
siamese cats
hydrocephalus
acquired:
mechanical or n. dysfuntion of any rectus mm.
CN III - D, V & M rectus mm & v. oblique
CN IV - d. oblique
CN VI - retractor bulbi & L rectus
what are 2 considerations for proptosis px
vision - poor (>75% blind d/t ON trauma)
globe retention - variable
if >3 rectus mm torn poor px
what is 1 of proptosis complicatons
strabismus - medial rectus is shortest & most easily torn
tarsus
The fibrocartilagenouslayer of the eyelid that contains the meibomonianglands (aka tarsal glands). This is the holding layer surgical eyelid closures
Meibomian glands
These are glands within the tarsal layer of the eyelid that produce lipid, or, sebum, to the tear film. This is the outermost, or most external layer of the three-layered tear film
Ptosis
drooping of the eyelids (most often evident by upper eyelid drooping) caused by sympathetic denervation to the eyelid.
lagophthalmos
incomplete eyelid closure/coverage of the eyeball
blepharospasm
Spasm of the orbicularis oculi muscle resulting in eyelid closure. AKA squinting
trichiasis
Hairs growing from normal skin reach the corneal and/or conjunctival surface. Technically speaking, entropion causes trichiasis, however, trichiasisis most often used to describe hairs from the nasal folds (nasal fold trichiasis) that are directed toward the eye in brachycephalic dog breeds.
distichia
cilia (eyelashes) which emerge from the Meibomian (tarsal) glands
ectopic cilia
cilia (eyelashes) protruding through the palpebral conjunctiva. These hairs typically cause severe, intermittent pain and often cause corneal ulceration. They most commonly arise from the 12 o’clock eyelid position
what are the 4 layers of the eyelid
Skin and reference points
Muscle
Tarsus and Meibomian glands
Conjunctiva
tarsus is fibrocartilaginous support for Meibomian glands
main function of eyelid skin
sensory protection
what are the clinically relevent eyelid muscles
what do they do
which CN innervates
what will dysfunction cause
Orbicularis oculi
Closes the eyelids like a zipper
CN VII (general somatic efferent) innervation
Dysfunction will cause lagophthalmos
Levator palpebrae superioris
Opens the upper eyelid
CN III (general somatic efferent) innervation
Dysfunction will cause ptosis
Müller’s muscle
Opens the upper eyelid
(General visceral efferent) sympathetic innervation
Dysfunction will cause ptosis
how does the palpebral conjunctiva look relative to bulbar conjunctiva
slightly hyperemic
what is the key concept to remember about entropion
This is an abnormal relationship of the eyein relation to the eyelids.
•
NEED TO IDENTIFY THE CAUSE OF THE IMBALANCE BEFORE TREATING!!!
what are 2 etiologic catagories for entropion
Anatomic entropion –the eyelids are not appropriately conformed to the eye and its presence is unrelated to ocular pain
Hereditary
Acquired
Blepharospasmassociated entropion –Ocular pain stimulates active globe retraction and an altered eyelid to eye relationship.
what is important to remember about hereditary entropion
Hereditary* -It is important to remember that dogs can ‘grow into their faces’. Permanent correction may not be necessary until 6-9 months of age
what are the hereditary causes of anatomic entropion
Abnormal canthus
common in brachycephalic dogs
Abnormal palpebral fissure
Often too large/loose in hounds and giant breeds
Excessive facial folds
what is the vicious cycle of blepharospasm associated entropion causes
Chronic ocular surface pain –from keratitis, conjunctivitis, or both >>>>
Entropion>>>>
Chronic ocular surface pain –from keratitis, conjunctivitis, or both>>>>
Entropion>>>>
why do we care to differentiate anatomic & blepharospastic components
failure to assess the spastic comoponent can lead to over correction & ectropion
How can we differentiate anatomic & blepharospasm entropion
take away the ocular pain that induces blepharospasm
Now that you have identified the cause of the eye to eyelid imbalance, you need to determine if it is temporaryor permanent
T or F?
Why?
We wouldn’t want to permanentlyalter eyelid anatomy in an animal that has a temporaryproblem
Example: Entropion from dehydration-related enophthalmos
(septic dehydrated foals)
what is the name of the tech for permanent correction of entropion
Modified Hotz-Celsus
