Ophthalmic Exam - Anterior Segment Flashcards
What makes up the anterior segment of the eye?
lens and rostral
What history is important for collecting during an ophthalmic exam?
- travel history
- progression of problem
- past ophthalmic problems
- source of the pet
- if/when ophthalmic medications were given —> can alter findings
What is the most important tool for ophthalmic exams?
good focal light source and magnification
- can use condensing lens for indirect ophthalmoscopy
What is most commonly used to document changes on ophthalmic exams?
eye exam sheet to draw any findings
What are important components of diagnostic testing for ophthalmic exams?
- cotton swabs
- culturettes
- microbrushes for cytology of the cornea and conjunctiva
- fluorescein staining
- Schirmer tear test strips
- tonometer
- nasolacrimal cannula flush
What topical anesthetic and dilators are used for ophthalmic exams?
proparacaine - topical anesthetic
tropicamide (short-acting), atropine (longer acting)
What is the most important first step to the ophthalmic exam?
observe the patient without touching them right away
- presence of vision or pain
- gross appearance of eyes, face, head position, and symmetry
- retropulse globes
What is phthisis bulbi?
small globe, loss of tissue
What is buphthalmos? Exophthalmos? Enophthalmos?
enlarged globe
protruding eyeball
sunken in eyeball
What is strabismus?
eyes pointing in the wrong direction
How should ocular discharge be observed?
clean from patient’s eye and note color, amount, and which eye it came from —> due to ocular disease
(not common to completely rinse eyes before ocular tests)
What does the palpebral reflex test? What are the afferent and efferent innervations tested?
feeling around eye and ability to blink —> want to keep patient from seeing the hand so they’re not responding to the sight of the hand
- AFFERENT = trigeminal nerve (V), maxillary = lateral; ophthalmic = medial
- EFFERENT = facial nerve (VII)
What does the menace response determine? What are the afferent and efferent innervations tested?
vision - patient should blink as hand approaches
- AFFERENT = optic (II)
- EFFERENT = facial (VII) - blinks!
What are 2 abnormal responses to a menace response?
- facial nerve paralysis can cause the globe to retract because the patient is unable to blink (abducens/VI innervates retractor bulbi)
- it is a learned behavior so kittens and puppies will not have it until 12 weeks and farm animals will develop it within 1-2 weeks
How is the menace response performed correctly?
visual stimulus only - no air should be hitting the eyes, so keep fingers open
- test from different angles and cover the contralateral side
How is a maze test performed?
have the patient in an unfamiliar environment and set up obstacles to see if they can make their way around
- make sure there’s enough room to move and it is performed in light and dark conditions
- lobby to exam room is commonly sufficient
What is the purpose of testing tracking?
shows movement detection in light and dark conditions
- good for puppies and kittens that would not have an accurate menace
- false negatives common, make sure the pet’s attention is gained
What is anisocoria?
asymmetry of pupils
What is miosis? Mydriasis?
constricted pupil
dilated pupil
(longer word = larger pupil)
What is dyscoria?
abnormal pupil shape
How is pupil size assessed? What should be seen?
direct ophthalmoscope with a weak light source and at a distance in light and dark conditions
outline of pupil by getting tapetal reflection
What controls the pupillary light reflex? What does it test?
PSNS
subcortical light perception
What are the 2 normal responses of the PLR?
- DIRECT - eye that light is being shone into has pupil constriction
- INDIRECT - ipsilateral eye constricts in response to light source
When is the dazzle reflex most commonly performed? What does it test?
when pupils are unable to be observed
complete path is not known, but it is only present when the optic nerve is intact to the midbrain, allowing for subcortical light perception
What is used to perform a dazzle reflex? What is the normal response?
bright (LED) light
bilateral partial eyelid blink
What are the top 3 diagnostics used for ophthalmic exams? What are they essential for diagnosing?
- Schirmer test
- corneal stains
- tonometry
(usually in this order)
“red eye” - glaucoma, ulcers, uveitis, conjunctivitis
What is the purpose of the Schirmer Tear Test I? What does it diagnose? When is it performed?
quantifies aqueous tear production (basal + reflex)
dry eye disease
prior to the application of any eyewash or topical anesthesia
How is the Schirmer teat test I performed?
- fold at notch while still in package
- place in the lateral lower eyelid
- leave for a minute
- read the mm/min that the tears flow immediately
What is the normal value for a Schirmer tear test? What do abnormal values indicate?
> 15 mm/min
- 11-14 = early or subclinical KCS
- 6-10 = moderate-mild KCS
- < 5 = severe KCS
How does the fluorescein stain work? What does it diagnose?
indicates ulcers by adhering to exposed stroma
epithelial and stromal corneal ulcers
How is a fluorescein stain performed?
- moisten stain strip with eye wash
- touch it gently to the conjunctiva and allow the animal to blink and then rinse
- observe with blue cobalt light for most accurate interpretation
What is the purpose of tonometry? What is the normal range?
measures intraocular pressure (IOP)
- 10-25 mmHg
- eyes of the same dog should not differ more than 5 mmHg
What is tonometry used to diagnose? What commonly affects pressures?
- glaucoma = higher pressure
- uveitis = lower pressure
where eye sits - brachycephalic dogs are normally on the higher end of pressures
How is tonometry performed? What is used for the comfort of the patient? What is an exception?
gently bounce the tonometer off the corneal surface at a 90 degree angle
topical anesthesia - proparacaine
rebound tonometry (tonovet) does not require topical anesthesia, like applanation (tonopen) does
What 3 actions can avoid falsely elevated IOP?
- gentle holding of the animal under the chin (not around the neck)
- head kept in the same position for all measurements
- eyelids should be held open gently to avoid pressure on eyeballs
What equipment uses rebound tonometry? How does it work?
Tonovet
electromagnetic probe measures IOP based on how quickly the eyeball rebounds to rest —> probe must be held upright
What equipment uses applanation tonometry? How does it work? What are the 2 major downfalls?
Tonopen
estimates IOP based on the pressure needed to flatten the cornea (needs topical anesthetic!)
- higher learning curve
- underestimates IOP
What is the purpose of using a transilluminator to examine the anterior segment?
light shone tangentially and moved to different angles to highlight corneal opacities, edema, and anterior chamber
How can the nictitating membrane be examined? When is this especially done?
- gentle pressure on the globe can make the NM protrude
- place proparacaine and cotton-tipped swabs or forceps and good lighting/magnification to look adequately +/- anesthesia
FB - cactus thorns, grass awns
How should the anterior chamber look upon exam? What is assessed? How?
optically clear
depth and clarity
direct ophthalmoscope with slit beam or dot —> not using aperture, just a light source —> hold closer to patient to decrease light dispersion
How does the anterior chamber observed with light?
should be able to see clear aqueous humor between reflections off the cornea and iris/anterior lens capsule
What is an aqueous flare?
protein, fibrin, or RBCs in the anterior chamber causes the Tyndall effect (fog in headlights) where the beams of light on the cornea and anterior lens capsule look like one beam, resulting in a hazy chamber
Aqueous flare:
protein in chamber = hazy
How is retroillumination performed?
ensure the patient’s pupil is dilated and the room is dark and use light at an arm’s distance to get a tapetal reflection that can illuminate smaller defects and allow examination of the lens for opacities
Retroillumination:
hazy lens
