Ophthalmic Exam and Tests Flashcards
bottle with red lid for ophthalmic exam contains what?
topical mydriatic
type of lends we use for fundic exam
20 dioptre lens
- Dazzle reflex:
CN II, VII
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Illuminate one eye with transilluminator without touching the eyelids
o Blink reaction will occur (CN II & VII)
Alternatively hold eyelids open and shine the transilluminator
o Retraction of ocular globe with prolapse of third eyelid (CN II & CN VI)
Sub-cortical reflex involving retina, CN II (afferent), and CN VII or VI or (efferent)
- Menace response:
CN II, visual cortex, VII
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Direct hand motion towards the eye without creating an air current
o Blink reaction will occur
o Menace from the front of the animal (stimulates the lateral retina) and also from the
lateral side (stimulates the medial retina)
Stimulation of CN II (afferent), visual cortex and CN VII (efferent)
Learned response and may take several weeks to develop after birth
- Palpebral reflex:
CN V, VII
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Touch the medial canthus, lateral canthus and then drag index finger along the entire palpebral
fissure to ensure complete reflex
o Blink reaction will occur
Stimulation of ophthalmic (medial canthus) and maxillary branch (lateral canthus) of CN V
(afferent) and CN VII (efferent)
- Pupillary reflex:
CN II, III
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Verify presence of anisocoria: at a distance of 2-3 feet, looking through the direct
ophthalmoscope at the setting “0”
Direct pupillary light reflex: dim-lit environment
o Transilluminator: illuminate the pupil with the beam of light going
o from nasal to lateral aspect
o Constriction of illuminated pupil (miosis)
o Sub-cortical reflex involving CN II (afferent) and CN III (efferent)
Indirect pupillary light reflex: dim-lit environment
o Transilluminator: illuminate the pupil directly for 30 seconds and rapidly change sides to
verify that the opposite pupil is in miosis since 50-75% of afferent fibres decussate to
the opposite side.
Note: Abnormal reflexes can be due to a variety of factors: for example, one application of 1%
atropine can last up to 24 hrs or longer if successive applications have been done; posterior
synechiae can also impair the iris sphincter muscle and not allow the reflexes to be seen; severe
uveitis or Horner’s syndrome will cause the pupil to become markedly miotic and impair the
direct pupillary reflex, however, the indirect should be present if the other eye is normal.
- Oculocephalic reflex (physiological nystagmus):
hysiological nystagmus:
- CN VIII, III, IV, VI
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Move head from side to side, up and down
o Saccadic movement of ocular globe
- Globe position:
CN III, IV, VI
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Note any strabismus via dysfunction of CN
o CNIII: lateral and dorsal strabismus
o CN IV: rotation of globe
o CNVI: medial strabismus
Dysfunction of sympathetic trunk: Horner’s syndrome
o Enophthalmia
o Ptosis of upper eyelid
o Protrusion of third eyelid
o Miosis
- Vision:
retina, CN Il, visual cortex
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Maze test: obstacle course in normal light and dim-lit environment
strabismus types, and cranial nerves involved
lateral strabismus
- oculomotor n. paralysis:
* exotropia
* mydriasis (dilated pupil)
* ptosis (droopy lid)
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medial strabismus
- abducens n. paralysis:
* esotropia
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rotation strabismus
- trochlear n. paralysis:
* Left extorsion (rotation) with deviation of the pupil from lack of dorsal oblique m. function
Sympathetic trunk denervation in Horner’s syndrome
midbrain > T1-T3 > preganglionic > cervical ganglion > through ear > post-ganglionic > eye
horner’s syndrome signs
- ptosis of upper lid
- enophthalmia
- miosis (can see on photo)
- elevated third eyelid
direct ophthalmoscope use
- evaluation of ocular structures, examiner must be 4-8cm from ocular globe
- roulette selects dioptre best for various structures
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Place the instrument on your brow and approach the instrument 2-4 cm away from the patient’s eye
Settings:
o Dioptre “20” (eyelids and cornea)
o Dioptre “15” (anterior chamber)
o Dioptre “12-10” (lens)
how to evaluate posterior segment (fundus)
- Use of transilluminator and 20 dioptre lens
- Straight arm, same height as patient
- Light source by examiner’s eye
How to examine behind the third eyelid:
Apply drops of topical anaesthesia
Grasp horizontal cartilage with non-teethed thumb forceps
Lift the third eyelid up and away from the corneal surface
Examine the bulbar aspect of the third eyelid for anomalies
How to examine the ocular structures of the anterior segment (eyelids to lens)
With the head loupes and transilluminator
how to dilate pupil for fundic exam, and how to directly and indirectly examine
Dilate pupil with 1% tropicamide for fundic examination
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15 minutes for dilation
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Direct ophthalmoscopy:
o Dioptre “0” (retina)
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Indirect ophthalmoscopy:
o Use of the transilluminator and 20 dioptre lens
o The image is an inverted mirror image of the real structure
o Hold light source at the level of your eye
o Obtain a tapetal reflection
o Place lens 4-8 cm from the animal’s eye with the white line of the lens towards the patient
Note any lesions at the level of the optic nerve head, vasculature and tapetal and non-tapetal
(brown) areas
Lack of pigmentation could be a variance of normal if the patient has a colour dilute coat.
Schirmer Tear Test
- use?
- how to?
- evaluates the basal and reflex tear production (aqueous layer)
Must be done prior to manipulation of the eyelids or application of drops
Make sure that hands and fingers are dry
Fold strip at notch and insert in the ventral conjunctival fornix
Close eyelids with your fingers to secure strip between eyelids
Leave strip in for 60 seconds and then record amount of tear production
Normal range: 15-25 mm/min
Fluorescein
- use
- how to
detection of corneal ulcers
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Wet the strip with eye irrigating solution and then gently touch the dorsal sclera (avoid touching the cornea)
Rinse off excessive dye with eye irrigating solution and cotton balls
With the cobalt blue filter on the direct ophthalmoscope in a dim-lit environment: illuminate the cornea and record any dye retention
May be seen leaking from nostrils: indicates that the nasolacrimal system is patent (Jones test)
Jones test:
- use
- how to
detection of patent nasolacrimal system
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Instill large amount of fluorescein on conjunctiva
Wait 2-5 minutes in order to see passage of dye to the nostrils
o May need to rinse in order to add more fluid for passage into duct
Brachycephalic breeds and cats may not be positive due to anatomy
Tonometry
- use
- methods
detection of intraocular pressures
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1. Schiotz : indentation tonometer (force to indent cornea)
- Instill topical anesthesia
- instrument is vertical
> Avoid tipping of instrument
- Contact fully cornea by going ½ down
- Convert scale reading to mmhg
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2. Tonopen: applanation tonometer (force to flatten cornea)
* Instill topical anesthesia
* Keep instrument parallel to the floor (perpendicular to the cornea)
* Avoid tipping the instrument as shown in the photo below
* Ensure that the tip contacts the cornea fully
o Gently rub or poke the cornea for measurements (dont indent cornea)
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3. Tonovet: rebound tonometer (bounce of cornea)
* The pin should be parallel to the floor
* You can turn the instrument (keeping the pin parallel, but avoid tipping the instrument)
cytology for eye
- how to
- detection of cell population
To be done after application of topical anaesthetic drops
Cyto-brush (MicrobrushTM) or dulled scalpel blade or Kimura spatula
Gently rub lesion at its periphery
Wrights or Gram stain to identify bacteria or presence of fungal hyphae
Essential for complex (infected) ulcers
Culture of eye
- how to
- detection of micro-organisms
Best done before application of drops
For best results: moisten culture tip before applying it to cornea
Gently rub lesion at its periphery
Submit for aerobic and fungal culture and sensitivities
o Contact laboratory and pick antimicrobials that are commercially available as ophthalmic preparations
Essential for complex (infected) ulcers
Takes at minimum 24-28 hours for results
Normal conjunctival flora of most animals: gram positive
Seidel’s test (Waterfall sign)
- what its for
- how to
detection of corneal perforation with leakage of aqueous
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Instill fluorescein on sclera and hold eyelids open
o Alternatively, apply topical anesthesia and then directly paint the lesion with the
fluorescein strip
Hold cobalt blue filter and look for clear or dark river emanating from the corneal wound
(leakage of aqueous)
