Ophthalmic Exam Flashcards
What ophthalmic disease is associated with Merle coat color?
Merle ocular dysgenesis
What history questions are important to ask during an ophthalmic exam?
- Duration of problem
- Unilateral vs bilateral
- Difficulty seeing
- day vs night vision
- Signs of pain
- squinting, rubbing at eye
- ocular discharge
- serous, mucoid, purulent
- Color change
- redness, cloudiness
- Medications
- duration, frequency, response
- General health concerns
- Other pets in the households
What supplies are needed for an ophthalmic exam?
- Quiet dark room
- Magnification
- Optivisor, loupes, otoscope
- Finoff transilluminator
- Schirmer tear test strips
- Fluorescein dye/eyewash
- Direct ophthalmoscope
- Indirect lense
- 28, 20 diopter
- Proparacaine (anesthetic)
- Tropicamide (mydriatic)
When should animals be sedated for ophthalmic exams
- Miosis/mydriasis (constricted/dilated pupil)
- Third eyelid protrusion/ventral globe rotation
- Decrease tear production and alter IOP
What observations can be made about the animal without the use of ophthalmic instruments?
- visual vs. nonvisual behavior
- facial symmetry
- Size and Shape of the orbit/globe
- ocular discharge
- eyelid position
- Ocular opacities
- BCS
- Temperament
What tests make up the Neuro-Ophthalmic Exam?
- Menace response
- Pupillary light reflex (PLR)
- Palpebral reflex
- Corneal reflex
- Dazzle reflex
What is the Menace Response and what is it testing?
- Stimulus: motion of hand/fingers coming toward the eye
- Receptor: retina
- Afferent: Optic nerve (CNII)
- Efferent: Facial nerve (CNVII)
- Effector: Orbicularis oculi
- Response: Blink
What are key points to remember about testing the Menace response?
- The opposite eye should be covered
- Don’t touch the facial hairs with testing hand
- Response is absent in puppies <4mo as it is a learned response
What is the Pupillary Light Reflex (PLR) and what is it testing?
- Stimulus: light
- Receptor: Retina
- Afferent: optic nerve (CNII)
- Efferent: Oculomotor (CNIII)
- Effector: Iris sphincter muscle
- Response: Pupillary constriction
- Direct PLR
- Indirect/consensual PLR
What is the PLR pathway?
- Optic nerve to Optic chiasm
- Optic tract
- ~20% of fibers to pretectal nuclei
- Decussation (majority of fibers)
- From Pretectal nuclei to Parasympathetic nuclei of the Oculomortor nerve (CNIII) (Edinger Westphal nuclei)
- Parasympathetic fibers of CN III synapse in ciliary ganglion
- short posterior ciliary nerves terminate in the iris sphincter
What are some key points of the PLR pathway
- Direct PLR = constriction of the stimulated eye
- Indirect/Consensual PLR = Constriction in contralateral, unstimulated eye
- PLR response does not test vision
- Fibers for PLR branch off the optic tract before the Lateral geniculate nucleaus
- Animals blind from cortical disease can have normal PLRs
- Animals with negative PLRs can still be visual
- Fibers for PLR branch off the optic tract before the Lateral geniculate nucleaus
What is the Palpebral/corneal Reflex and what is it testing?
- Stimulus: Touch
- Receptor: Skin/cornea
- Afferent: Trigeminal nerve (CNV)
- Efferent: Facial nerve (CNVII)
- Effector: Obicularis oculi
- Response: Blink
What is the Dazzle Reflex and what is it testing?
- Stimulus: Bright light
- Receptor: Retina
- Afferent: Optic nerve (CNII)
- Interneuron: CNS/Subcortical
- Efferent: Facial nerve (CNVII)
- Effector: Obicularis oculi muscle
- Response:: Blink
What are key points of the Dazzle Reflex?
- Especially useful when fundus can not be visualized
- hyphema (accumulated red blood cells (RBC) in the anterior chamber of the eye)
- Severe corneal disease
- Cataracts
- No need to test if Menace Response is positive
How is the Orbit examined
- Assess orbital symmetry
- Palpation
- Globe and TEL position
- Retropulsion of globe
- Oral examination
- Pterygopalatine fossa caudal to last upper molar
- Orbital disease
- Pain on opening mouth
- Inability to open mouth
What is the Adnexa and how is it examined?
- Adnexa:
- eyelids, conjunctiva, nasolacrimal system
- Variations of normal for species/breed
- Circumferential third eyelid (red arrow)
- Nonpigmented TE margin
- Haired lacrimal caruncle
- Examine Upper and lower eyelids
- General: palpebral fissure size, skin condition, discharge, blepharospasm
- Lid apposition and closure
- Incomplete = lagophthalmos
- Facial hairs contacting eye
- nasal fold, or medial canthal trichiasis
- Eylid masses
- Eyelid lacerations
- Eyelids rolling inwards (entropion)
- Eyelids rolling outward (ectropion)
- Lid Margins and underside of lids
- Distichia (eyelids arise from melbomian glands)
- ectopic cilia
- impacted melbomian glands
What is this condition
- Macropalpebral fissure
- can be normal breed variation (shitzus, etc)
How is the Nictitating membrane examined?
- Retropulse the globe
- examine for masses, scrolled cartilage, prolapsed glands
- Examine behind third eyelid for foreign bodies
- Topical anesthetic
- grasp w/forceps and evert or pull forward with a cotton tipped swap
How should the Conjunctiva and sclera be examined?
- Conjunctiva:
- Evaluate bulbar and palpebral surfaces for injected vessels, bleeding, swelling, masses, foreign bodies, etc
- Sclera:
- evaluate for episcleral vessel congestion, masses, etc.
Subconjunctival hemorrhage
Nodular granulomatous episcleritis
What should the Anterior Chamber be examined for?
- should be clear
- Anterior Chamber depth
- Aqueous flare
- protein in aqueous humor
- Use a focal light source
- Hyphema
- blood in anterior chamber
- Hypopyon
- WBC in anterior chamber
- Masses
- cysts, tumors
- Anterior lens luxation
What should the Cornea be examined for?
- Should be clear
- Red: vessels
- Blue: edema
- White: Scar, lipid, WBC, calcium
- Brown: pigment, foreign bodies
What should the Iris/pupil be examined for?
- Iris:
- color change
- Masses
- Hemorrhage
- Pupil:
- Dilated / Constricted
- Different sizes (anisocoria)
- Abnormal shape (dyscoria)
What should the lens be examined for?
- Position of lens
- Should be Clear
- Cloudiness from the lens hardening- Nuclear sclerosis
- can still see through!
- Opacity in the lens - cataract
- diminishes vision
- Cloudiness from the lens hardening- Nuclear sclerosis
How is the posterior of the eye examined?
- Includes: Vitreous, retina, optic nerve head
- Evaluate:
- ONH size, shape, and myelination
- Retinal vasculature
- Tapetal reflectivity
- Dilation of pupil
- 1% Tropicamide
- Cholinergic antagonist
- 1% Tropicamide
What are the options for Ophthalmoscopy?
- Direct Opthlamoscopy
- Indirect Opthalmoscopy
What is Direct Ophthalmoscopy
- Give Real, upright image
- Higher magnification
- Monocular view
- Small field of view
- Useful for close examination of optic nerve/retinal lesions
- Dangerous w/ some patients
What is Indirect ophthalmoscopy
- Image is upside down and backwards
- Lower magnification
- Binocular or monocular view
- Larger field of view
- Higher diopter = lower magnification
- lower diopter = higher magnification
What diagnostic tests can be done on the eye?
- Culture and sensitivity
- Cytology
- Schirmer Tear Test (STT)
- Fluorescein dye
- Tonometry
- Nasolacrimal Flush
When/How is culture and sensitivity performed on the eye?
- Suspected infection
- *Bacteria can frequently be cultured at low numbers form normal conjunctiva!
- Staphylococcus spp, streptococcus spp, Cornybacterium, and Bacillus spp
- *Bacteria can frequently be cultured at low numbers form normal conjunctiva!
- Use Moistened mini-tip swabs
- Provide Topical anesthesia
- Avoid contamination of sample, and of eye
- For ulcers - culture from the periphery
- Run aerobic bacterial +/- fungal culture
Why is atropine not used to dilate eyes in animals?
effects are long lasting (2 weeks!)
How should a cytology sample be taken from the eye?
- Provide topical anesthetic
- Use: Kimura platinum spatula, blunt end of a surgical blade, or a cytobrush
- Do NOT use a cotton swab - does not transfer cells to the slide well
What is the Schirmer Tear Test (STT)?
- Measures aqueous component
- Basal tears
- Reflex tears
- Prior to topical anesthesia (decreases tear production)
- Remove strip after 60 sec
- Normal > 15mm/min dog
- Do not routinely perform in Horses or cats
When is Fluorescein Stain?
- Corneal ulcer
- Jones test
- Tear film break up time
- Seidel test
How are corneal ulcers tested for?
- Water soluble dye
- Intact corneal epithelium is hydrophobic (lipophilic) and does not retain fluorescein
- hydrophilic stroma retains fluorescein
- Descemet’s membrane is hydrophobic and retain fluorescein dye
- Application:
- Moisten strip with saline
- Apply to ocular surface
- Rinse
- Assess for dye retention - Cobalt blue light
What is the Jones test
- Evaluates patency of nasolacrimal system
- Apply fluorescein stain to ocular surface rinse
- Hold nose down and examine nostrils
- Examine oral cavity
- Normal passage < 5 min
What is Tear Film Break-up Time?
- Tear quality assessment
- Moisten strip with saline and apply to cornea
- Do NOT rinse
- Blink eyelid
- Hold lids open and monitor for “dry spots”
- Normal tear break-up time >20 seconds
What is the Seidel Test?
- Aqueous humor leakage
- Corneal lacerations
- Rupture ulcers
- Surgical incision
- Apply Fluorescein
- Do NOT rinse
- If leaking will create a river
What is Tonometry?
- Measures intraocular pressure
- Normal 15-25 mmHg
- Applanation - Tono-Pen®
- Induction-impact - Tonovet®
What is applanation?
- Measures force required to flatten corneal surface
- Fast and easy
- Technique - easy to falsely elevate
- topical anesthetic (proparacaine)
- Restraint
- Eyelid retraction
- Measurement:
- 5% 10% 20% or >20% variance
- lowest reading (5% or less)
What is Induction-impaction tonometery
- Measures rebound action of magnetic probe as it contacts the cornea and bounces back
- Does not require topical anesthetic
How is a nasolacrimal flush done?
- Topical anesthetic
- cannulate superior puncta w/ flexible catheter or canula attached to a syringe
- Flush saline form superior to inferior puncta, then occlude inferior puncta w/ digital pressure and flush into the nasal cavity