Eye examination Flashcards
To begin an eye exam, where do you start
at the healthy eye
(after a thorough anamnesis and observing the patient from afar)
Monitor the movement and behavior of the animal in the room prior to examination.
A thorough eye exam should include: (7)
- Hands-off distant examination of head, eyes, eyelids and skin around the the eyes.
- Innervation & vision assessment – blinking, Menace response, Pupillary light reflex – direct and consensual, cotton ball/tracking test
- Schirmer Tear Test (mm/1 min)
- Fluorescein test – for exluding the corneal ulcer
- Examination with local light and magnification, local anesthesia if needed, Alcaine 0,5% ®
(eyelids, distichia, ectopic cilia, spots in cornea, foreign body, anterior chamber, iris). - Tonometry (IOP mmHg)
- Examination of eye fundus with direct ophthalmoscopy without mydriasis at the distance of a straight arm + near ophthalmoscopy ca 10 cm distance from the eye till you see blood vessels, pattern of fundus, optic disc etc.
Difference between direct and indirect ophthalmoscopy.
direct is handheld, indirect is a headset/loupes
In direct, the examiner looks directly through the device’s viewing aperture to visualize the fundus (the interior surface of the eye). The light from the instrument illuminates the retina, allowing the examiner to see its details.
Direct ophthalmoscopes provide a limited field of view of the retina, usually around 5-15 degrees. This narrow field of view can make it challenging to examine the entire retina at once.
Direct provides an upright, unreversed image of around 15 times magnification
Indirect consists of a light source mounted on a headband or handheld device, along with a condensing lens. They also require the use of a handheld lens, known as a condensing or viewing lens.
In indirect, the examiner sits at arm’s length from the patient and holds the condensing lens in front of the patient’s eye. The light from the ophthalmoscope is used to illuminate the retina, and the examiner views the magnified image of the fundus through the condensing lens.
Indirect ophthalmoscopes provide a wider field of view compared to direct ophthalmoscopes, typically around 20-30 degrees. This broader field of view allows for better visualization of the peripheral retina and a more comprehensive examination.
produces a reversed, inverted image magnified 2 to 5 times
provides an upright, unreversed image of around 15 times magnification and,
provides a limited field of view of the retina, usually around 5-15 degrees
Direct ophthalmoscopy
produces a reversed, inverted image magnified 2 to 5 times and,
provides a wider field of view, typically around 20-30 degrees.
Indirect ophthalmoscopy
“Extra” eye examinations: (4)
If needed:
- Examination of eye fundus with indirect ophthalmocopy with mydriasis. (Use Tropicamide 0,5-1%)
- Analyses (bacteriology, PCR, gene tests, cytology)
- Examination under general anesthesia
- Cannulation and flushing of naso-lacrimal ducts
When glaucoma is suspected, the pupil should not be dilated, as this narrows the iridocorneal angle.
True Ocular Emergencies include: (5)
- Acute onset blindness (eye dz or neuro (like encephalopathies))
- Acute onset of red or cloudy eye
- Acute onset painful eye (squinting or excessive blinking)
- Anything dangling from the eye (including the eye itself – proptosis)
- Trauma of the eye
What drug group is especially important for ocular emergencies?
NSAIDs
Basically always give.
You can even recommend the owner give paracetamol in special situations (but not for cats).
Ocular emergency Advice for the owner by phone (5)
- The most important thing is that the animal is not allowed to cause further damage-> Elizabethan collars help prevent trauma.
- Rinse the eye gently with artificial tears or special eye cleaning solution, or a sterile saline solution or tap water even.
- Don’t advise to give any „home “ medication (special cases may get paracetamol though)!
- If owner says, or description seems like proptosis of eye: owner should keep the eye moist with saline, water, artificial tears and immediately visit the vet.
- If owner says, or description seems like contact with chemical solution/chemical burns: owner should cleanse eyes with a sterile saline solution, or tap water immediately for at least 20 min and then immediately visit the vet.
Equine blepharospasm requires… for exam.
Local blocks as its impossible to manually open.
How do you describe red looking sclera?
Its actually bulbar conjunctiva that you see as hyperemic.
If you see rhinitis with epiphora and blepharospasm in a feline patient - whats your suspicion?
rhinitis is more typical to feline herpes virus
oral ucleration is more typical to calici
“herpes is epitheliotropic” thus it favors the nose whilst calici more so causes stomatitis
Schirmer tear test normal results:
Dog: 15- 25 mm/1 min. Values between 10
and 15 mm may be caused by transiently
lowered tear production because of
stress.
Cat: 12- 22 mm/1 min, but the values may
vary, and cats are difficult to measure.
Sheila, 8 y, female cavalier king charles spaniel,
chronic blepharitis, inflammation of conjunctiva and cornea, totally pigmented, not transparent cornea.
keratoconjunctivitis sicca
Nnormal vein in part of bulbar conjunctiva.
Episcleral and scleral blood vessels congestion
+/- conjunctival blood vessel congestion/conjunctival hyperemia can indicate?
Signs of intraocular diseases.
Pictured eye has high intraocular pressure - glaucoma.
typical cat breed for entropion
maine coon
3 light source and magnification options for eye exams:
focal light source
biomicroscope
loupes
What is PVR assessment?
PVR in this context likely stands for “Pattern Visual Response”.
It refers to a type of test used to assess the function of the visual pathway from the eyes to the brain.
This test helps in localizing abnormalities in vision-related neural pathways and detecting issues in the central nervous system (CNS), such as optic nerve disorders and neuro conditions etc.
Explain the PLR and why you test it.
The pupillary light reflex (PLR) is a neurological test used to assess the integrity of the visual and autonomic pathways controlling pupil constriction. It evaluates both the direct and consensual (indirect) responses of the pupil to light stimulation.
This test is particularly useful in veterinary ophthalmology and neurology to detect lesions affecting the eyes, optic nerves, brainstem, or autonomic pathways.
Neural Pathways Involved in the Pupillary Light Reflex
The pupillary light reflex follows a pathway, involving both afferent (sensory) and efferent (motor) components:
Afferent
- Light enters the eye and is detected by the retina.
- Signals travel via the optic nerve (cranial nerve II) to the optic chiasm, where some fibers cross to the opposite side, others remain on the same side.
- Processed in the midbrain.
Efferent
- parasympathetic fibers via the oculomotor nerve (cranial nerve III)
- Short ciliary nerves then innervate the iris sphincter muscle, causing pupillary constriction (miosis).
Clinical Interpretation of Abnormal Reflexes:
Absent direct & consensual PLR in one eye,
normal in the other.
Possible causes:
Optic nerve (CN II) lesion in the affected eye (e.g., optic neuritis, retinal disease).
Clinical Interpretation of Abnormal Reflexes:
Absent direct PLR but present consensual PLR.
Possible causes:
Oculomotor nerve (CN III) or iris sphincter dysfunction in the affected eye.
Clinical Interpretation of Abnormal Reflexes:
Absent consensual PLR but present direct PLR.
Possible causes:
Optic nerve lesion in the opposite (non-stimulated) eye.
Clinical Interpretation of Abnormal Reflexes:
Absent consensual PLR but present direct PLR.
Possible causes:
Optic nerve lesion in the opposite (non-stimulated) eye.
Clinical Interpretation of Abnormal Reflexes:
Both pupils dilated, unresponsive to light.
Possible causes:
Brainstem lesion affecting the midbrain (e.g., herniation, trauma, toxins).
Clinical Interpretation of Abnormal Reflexes:
Anisocoria (unequal pupils), one pupil does not respond.
Possible causes:
CN III, oculomotor nerve dysfunction (e.g., Horner’s syndrome, trauma, or tumors affecting autonomic pathways).
a normal PLR in a blind animal suggests
cortical blindness
Topical anesthesia options for eyes. (5)
Tetracaine 0.5%
Proxymetacaine (Proparacaine) 0.5% (Alcaine)
Oxybuprocaine (Benoxinate) 0.4%
Lidocaine 2% Gel
Chloroprocaine 3% Gel
Topical anesthesia, if spastic/painful eye.
For simple examinations one drop is applied.
The effect approximately one minute after application.
Topical anesthetics are not indicated as treatment in painful conditions, due to their tissue toxicity,
In animal with spastic eye
(blepharospasm) you must exclude:
- Foreign body in conjunctiva, cornea, under eyelids, and under nictitans membrane
- Aberrant cilia or hair (distichia or ectopic cilia)
Also Evaluate by staining with Fluorescein-Na solution for detecting corneal ulcer.
What are ectopic cilia?
abnormal hair follicles develop and grow through the conjunctiva, usually on the upper or lower eyelid, and can contact the cornea.
These misplaced cilia can cause irritation, discomfort, corneal ulcers, and even vision impairment due to chronic mechanical trauma.
Treatment typically involves surgical excision of the affected hair follicles to prevent recurrence.
Symptoms include excessive blinking (blepharospasm), tearing (epiphora), redness, and corneal ulcers.
Describe the FLUORESCEIN TEST
Place dye strip in syringe of NaCl or place a drop of NaCl directly onto end of strip.
One drop of the stain is applied on the cornea and
excess stain is rinsed off.
In areas with loss of corneal epithelium Fluorescein-Na will penetrate into the stroma causing a green stain.
Deep ulcers may go all the way down to the Descemet’s membrane.
Deep ulcers may go all the way down to the Descemet’s membrane.
The membrane will not stain but will present as a clear spot in the middle of the green stained walls.
Tonometry is the measurement of intraocular pressure (IOP), mmHg.
Indications: (6)
- Painful eye
- Red eye
- Cloudy eye
- Vision impairment
- Enlarged eye
- In breeds predisposed to glaucoma
beagle, husky, etc.
Normal intraocular pressure
in dogs?
in cats?
dogs is 15-25 mmHg
in cats 15-30 mmHg
Normal IOP diff between eyes ≤ 8mmHg.
Normal IOP diff between eyes
≤ 8mmHg.
IOP of > 30 mmHg over several days damages
the optic nerve and retina.
- IOP > 40 mm is painful and causes enlargement of the globe (buphthalmos).
Normal in dogs is 15-25 mmHg, in cats 15-30 mmHg.
enlargement of the globe
buphthalmos
IOP > 40 mm is painful and causes enlargement of the globe (buphthalmos).
IOP > 40-50 mm causes what to happen?
paralyses the sphincter muscle of the iris and causes mydriasis.
Normal in dogs is 15-25 mmHg, in cats 15-30 mmHg.
Lowered IOP indicates
intraocular inflammation (uveitis).
Normal in dogs is 15-25 mmHg, in cats 15-30 mmHg.
3 options for vision testing
obstacle course (with owner or treats at the end)
cotton ball test
swinging light test (look for head or eye movements)
The optic nerve is the afferent path both for vision and pupillary light reflexes. In the cat and dog, about two-thirds of the optic nerve fibres cross in the optic chiasm to the opposite side of the brain.
In the optic tract, about 80% of the nerve fibres project via the lateral geniculate nucleus to the visual cortex of the cerebrum, whereas about 20% go to the midbrain.
Normal function of the optic nerve can be tested in many ways. Practical testing includes: (4)
- The menace response
- The visual placing reaction (forelimbs onto tabletop)
- The pupillary light reflexes
- The dazzle reflex
A normal menace response requires
a normal visual pathway, (the sensory pathway),
as well as a normal facial nerve (VII), the motor pathway.
note that the menace reaction can be absent in animals with
cerebellar or facial nerve lesions, without the animal being blind, and that seriously ill animals may react poorly to the stimulus.
Signs of Collie Eye Anomaly
blindness
microphthalmia
enophthalmia
coloboma aka retinal hypoplasia (which can cause retinal detachment)
iris cyst, benign balls of iris tissue
persistent pupillary membrane
Many dog breeds are predisposed to glaucoma. Inspection of the iridocorneal angle, the drainage angle between the cornea and iris, may be indicated. In horses and cats the angle is easily visible, in dogs vision is obscured by the sclera.
So how is this examined in dogs?
gonioskopia
An extra curved lens, a gonioscopy lens, can be placed on the cornea after topical anesthesia for
inspection of the iridocorneal angle in the dog. However, this is not part of routine examination.
iris coloboma aka missing iris tissue, benign but can cause light sensitivity
classic signs of uveitis
blepharospasm.
episcleral or conjunctival hyperemia.
diffuse corneal edema.
miosis.
aqueous flare (indicative of protein or cells in the anterior chamber)
fibrin in the anterior chamber.
hypopyon.
hyphema.
In uveitis, production of aqueous is diminished, and the IOP is lowered.
Uveitis complications in horses.
Uveitis may be recurrent with variation in severity. This is of special importance in the horse where recurrent uveitis is a major cause of blindness.
Because of the intimate connection between the iris and the lens, untreated uveitis will lead to adherences.
The aqueous is not able to drain through the pupil and will accumulate behind the iris pushing it forwards. The iris will then block the drainage angle, and the eye develops secondary glaucoma finally leading to blindness.
Posterior uveitis affecting the choroid will show less dramatic signs, but the eye is red, and examination of the fundus (the back of the eye) will reveal pathologic changes.
What is the fundus reflex.
refers to the (varying color) reflection of light from the back of the eye, or fundus, observed when using an ophthalmoscope or retinoscope.
What is schiotzi?
old-fashioned tonometry
Normal IOP in horses.
10-37 mmHg
(wider normal range than other species)
