Ophthalmic examination Flashcards
What elements can be assessed in the distant ophthalmic examination?
- Facial symmetry
- Ocular symmetry
- Ocular discharge
- Eyes open or closed
- Size of palpebral fissure
- Position of third eyelid
What is the Purkinje image and what can it indicate?
- Is the reflection of image on surface of eye, e.g. corneal reflex
- Disturbed image can indicate poor tear film, irregular corneal surface etc.
What ophthalmic condition are Westies predisposed to?
Dry eye (keratoconjunctivitis sicca)
What ophthalmic condition are terriers predisposed to?
Lens luxation
What is hyphaema?
Blood in the anterior chamber of the eye
What are the common causes of hyphaema in the puppy?
- Congenital anomaly
- Trauma
What would hyphaema in a 12yo dog be suggestive of?
Intraocular neoplasm
What would hyphaema in a 12yo cat be suggestive of?
Systemic hypertension
What might uveitis in an entire female be indicative of?
Pyometra
What points should be addressed in an ophthalmic history?
- When problem started
- Gradual or sudden onset
- Progressive
- One or both eyes
- Pain
- Vision (day vs night, familiar vs unfamiliar surroundings)
- Change in appearance of eye
List the reflexes assessed in an ophthalmic examination
- Palpebral
- Menace
- Dazzle
- Pupillary light
- Vestibulo-ocular
What does the palpebral reflex assess?
Skin sensation and ability to blink, good to perform before other tests to avoid false negatives if cannot blink
What does the menace response assess?
Not true reflex, assesses vision (and ability to blink)
Compare the age at which the menace response develops in different species
- Dog and cats from 12 weeks old
- Present in foals at 1-2 days old
What does the dazzle reflex assess?
The ability to detect light
What is the dazzle reflex and what are the afferent and efferent pathways?
- Subcortical reflex
- Both eyes blink and possible head withdrawal
- Afferent: retina CN II, rostral colliculus, subcortical connections
- Efferent: CN VII
Why might false negatives occur with a PLR?
- Weak light source in daylight, not strong enough to elicit PLR
- Animal scared, stressed, high level of SNS tone (repeat at end of consult)
- Iris atrophy (age related atrophy of iris musculature)
What are the afferent and efferent pathways for the tracking reflex?
- Afferent: CN II
- Efferent: CN III, IV, Vi, VIII
What are the afferent and efferent pathways of the corneal reflex?
Afferent: V (ophth) branch
Efferent: globe retraction by CN VI, blink by CN VII
What is the Schirmer tear test used for?
Quantitative measurement aqueous part of the basal and reflex tear production
Explain the correct placement of the Schirmer tear test strip
Place more laterally in the eye - if too medial will not get the reflex component due to third eyelid preventing this
What would a normal STT value for a dog be?
15-25mm/minute
What would the following STT values in the dog indicate?
a: <10mm/min
b: 10-15mm/min
c: >25mm/min
a: Diagnostic for dry eye
b: Diagnostic for dry eye if supportive clinical signs present, ideal time to start treatment
c: over production i.e. ocular irritation
What would the normal STT values for a cat be?
- Much more variable than the dog
- 5-10mm/min very common, textbooks tend to say 17mm/min
What dioptre settings should be used for the following portions of the eye in direct ophthalmoscopy:
a: retina
b: lens
c: cornea
a: 0
b: 8-12
c: 20
What are the advantages of distant direct ophthalmoscopy?
- Highlight visual axis
- Assess pupil size and clarity of visual axis
- Opacities will be black and obvious e.g. cataract,, foreign body, ulcer
List the different methods of ophthalmoscopy
- Distant and close direct
- Monocular or binocular indirect
What is stained by fluorescein dye?
Corneal stroma
What are the normal intraocular pressures for:
a: dog and cat
b: horse
c: rabbit
a: 15-25mmHg
b: 17-28mmHg
c: 15-20mmHg
What IOP difference between 2 eyes is abnormal?
> 10mmHg difference
List the methods for tonometry in the small animal
- Digital tonometry (fingers)
- Indentation tonometry
- Applanation tonometry
- REbound tonometry
Describe the method for and evaluate the use of digital tonometry in small animals
- Place forefinger on globe through skin of upper eyelid, both eyes in unison for comparison
- Allows estimate of very hard vs very soft eye and some comparison
- Very inaccurate
Describe the method and evaluate the use of indentation tonometry in small animals
- Schiotz tonometer
- Cumbersome, needs practice
- Local anaesthetic drops on eye, tilt head back so cornea is horizontal
- Place foot on eye and measure degree of indentation of metal rod on cornea
Describe and evaluate the use of applanation tonometry
- Very accurate, good for all species, but expensive
- Local anaesthaetic drops
- Measures flattening of the cornea against disposable latex tip
Describe and evaluate the use of rebound tonometry
- Very accurate, good for all species, expensive
- Local anaesthetic not required
- Hold in horizontal position, measures how fast pin rebounds from eye
- faster rebound = harder eye
- Disposable probe, no contamination
What is the function of the Jones’ test?
Assesses patency of tear duct
Describe the method for the Jones’ test
- Apply flourescein to both eyes as normal
- Observe for a few minutes
- Positive: dye passes through nasolacrimal duct and visible at both nostrils within 2-5 mins in smallies, 5-20 mins in the horse
- False negatives common
What may lead to false negatives on a Jones’ test?
- Dog licks nose
- Accessory openings in mouth, need to look for green tongue, esp. in brachy breeds
- Insufficient dye
- Head too elevated
- Insufficient time
What is the purpose of the Seidel test?
Assessment of corneal integrity
Describe the method and indications for the Seidel test
- Indications: following removal of corneal FB, corneal laceration, suspicion of perforated corneal ulcer
- Flourescein dye applied to eye but not flushed, aqueous humour leakage detected by clear fluid pushing fluoresein away from site of concern
When is the use of corneal swabs indicated?
- Suspect bacterial infection
- Cats with ocular surface disease
- In order to perform bacteriology, fungal culutre, PCR tests (for viruses)
What are the most common causes of ocular surface disease in cats?
- Chlamydophila felis
- FHV-1
- also: Mycoplasma felis, feline calicivirus, Bordatella bronchiseptica
Describe the method for ocular swabbing
- Apply local anaesthetic drops to eye
- Retropulse globe through upper lid to protrude third eyelid
- Roll swab several times in front of third eyelid (for conjunctivitis) or cornea (for corneal ulcer, tough edge of ulcer gently)
Describe the method for performing a nasolacrimal flush
- Can be conscious with local in some dogs, rabbits and horses, unless inexperienced with technique
- In cats, small punctal opening so need GA
- Cannulate upper punctum, attach 2ml syringe of water/saline, flush gently, look for fluid at lower punctum
- Occlude lower punctum by external compression, continue flushing head down slightly, look for fluid at ipsilateral nostril
- In horse, go retrograde from nostrils up (easier to find)
- In rabbit, only have lower and no upper ppunctum
Describe the vestibulo-ocular reflex
- Aka dolls-head reflex, physiological nystagmus
- Stimulus: change head position side to side, up and down
- Normal response is that both eyes move together - fast phase in direction of movement, slow phase opposite to direction of movement
What is gonioscopy?
Assessment of iridocorneal drainage angle
How is gonioscopy performed and what are the indications for this?
- Anaesthetic drops on eye first
- Place contact lens on eye to look at drainage angle
- Used to assess if are predisposed to hereditary glaucoma mainly
What is slit-lamp biomicroscopy particularly useful for?
Assessment of depth and location of corneal lesions
What is the function of electroretinography (ERG)? How is it performed?
- Assessment of retinal function
- Eye equivalent of ECG
- Corneal electrode = contact lens
- Skin electrodes and light source used
- Produce waveform that demonstrates retinal function
What does electroretinography allow determination of?
Whether blindness is due to the eye or the brain
