Neuro-ophtho

Question 1

CN II

Answer 1

Optic nerve
Exits at optic foramen
Axons of retinal ganglion cell
Function - carry electrical signal from retina to brain

Question 2

CN III, IV, VI

Answer 2

All exit at orbital fissure
Function - Innervation of Extraocular muscles
III - Oculomotor
IV - trochlear
VI - abducens

Question 3

CN III

Answer 3

Innervates the DR, MR, VR, VO and levator palpebral superioris
– Helps you look up, toward the nose, down & centralize pupil by counteracting the dorsal oblique
- lifts upper lid
PSN Innervation to Iris sphincter muscle and ciliary body (miosis)

Question 4

Lesion to III causes what strabismus s

Answer 4

Down and out strabismus

Question 5

CN IV

Answer 5

Innervates dorsal oblique muscle - helps centralize pupil in counteracting the ventral oblique muscle

Question 6

Trochlear nerve lesion causes what kind of strabismus

Answer 6

Inward/cross eyed strabismus

Question 7

CN VI

Answer 7

Innervates lateral rectus and retractor bulbi
Moves laterally, sucks eye inward = moving 3rd eye lid

Question 8

Abducens nerve lesion leads to what kind of strabismus

Answer 8

Unilateral medial strabismus

Question 9

Remember 3

Answer 9

DO4LRRB6Rest3
Dorsal oblique - CN 4
Lateral recuts & retractor bulbi - CN 6
Rest of the muscles - CN 3

Question 10

CN V

Answer 10

Ophthalmic branch exits orbital fissure
Maxillary branch exits round foramen via rostral alar canal
Mandibular branch exits oval foramen

Question 11

CN V innervation

Answer 11

Ophthalmic brachial provides sensory to the orbit, medial canthus, conjunctiva and cornea
Maxillary branch provides sensory to lateral canthus
Mandibular provides to muscles of mastication

Question 12

CN VII

Answer 12

Exits stylomastoid foramen
Function - innervation to orbicularis oculi = blinking
PNS Innervation to lacrimal gland & 3rd eyelid gland

Question 13

VIII

Answer 13

Exits internal acoustic meatus
Functions to coordinate eye movement with head movement so vision isn’t blurry
Works with the medial longitudinal Faciculus

Question 14

CN X

Answer 14

PSN tone in decreasing heart rate - pressing on eyelids*
Beneficial for vagal maneuvers
Can be detrimental - oculocardiac reflex

Question 15

Parasympathetic input on CN III

Answer 15

Parasympathetic nucleus of CN III, aka Edinger-Westphal nucleus
• Innervation to iris sphincter muscle and ciliary muscles
• Functions: miosis and accommodation

Question 16

Parasympathetic input for CN VII

Answer 16

Parasympathetic nucleus of CN VII
Innervation to lacrimal /3rd eyelid glands
Functions: lacrimation & nasal wetting
neurogenic KCS: dry eye
Stimulation a Parasympathomimetics - pilocarpine
Inhibition w parasymatholytics/anticholinergic - atropine, glycopyrrolate

Question 17

Xeromycteria

Answer 17

Commonly occurs with neurogenic KCS
Dry eyes and dry nose

Question 18

Testing vision

Answer 18

Menace response
Cotton ball test

Question 19

Menace response

Answer 19

Afferent info - CN II
Efferent info - CN VII = blinking & CN VI = globe retraction
Not a reflex, its a learned response. Will be absent in young puppies/animals (<12 wks)

Question 20

cotton ball test

Answer 20

Evaluates CN II (afferent)
Tracking moving object w eyes

Question 21

Inconsistencies in results

Answer 21

Age - learned response vs reflex
Stoic animals
Pain (ocular or systemic)
Cats - wont menace
Exotics - birds/reptiles

Question 22

Testing sensation

Answer 22

Palpebral reflex - blinking in response to touch,
A info - CN V opthalmic branch/max branch
E info - CN VII
Corneal reflex - blinking in response to touch on cornea
A info - CN V ophthalmic branch
E info - CN VII (blink) and CN VI (globe retraction)

Question 23

Testing movement

Answer 23

Oculocephlic reflex - dolls eye reflex, moving head to Track movement
Afferent info - CN VII
Efferent info - CN III, IV, VI

Question 24

Dazzle reflex

Answer 24

Stimulated with bright light = blink and globe retraction
Afferent - CN II
Efferent - CN VII and CN VI
It’s a pain reflex due to bright light, its pre-cortical and does not signify vision

Question 25

Visual pathway

Answer 25

Nasal and lateral hemiretinas - optic nerve - cross over at optic chiasm - optic tract = Lateral geniculate nucleus = visual cortex

Question 26

PLR

Answer 26

Afferent - CN II Nasal & lateral hemiretinas - optic nerve - optic chiasm X - optic tract - retractable nucleus —> 2nd cross over 50% of fibers cross to ipsilateral side

Question 27

PLR efferent

Answer 27

efferent CN III Parasympathetic nucleus of CN III (edinger-Westphal nucleus) —> CN III efferent tract —> ciliary ganglion —> Irish sphincter muscle

Question 28

Vision vs PLR

Answer 28

Vision Requires function of millions of photoreceptors Cortical input and process aka higher centers in brain

Question 29

Vision vs PLR*

Answer 29

Doesn’t requires many functional receptors PLR Parasympathetic tone Pretectal nucleus Precortical response Reflexes dont see the higher centers of the brain aka reflexes don’t signify vision However this tract has a double cross over at axons and its not 50:50 in domestic species

Question 30

Direct response

Answer 30

Direct is an ipsilateral response which has a greater magnitude than consensual or indirect response

Question 31

100% cross over

Answer 31

Occurs in birds - 100% cross over means there will be no consensual PLR

Question 32

50% cross over

Answer 32

Species with 50% cross over, a direct and consensual response results in equal PLRs

Question 33

Abnormal PLRs Afferent lesions

Answer 33

Retina - retinal detachment/degeneration Optic nerve - neuritis, avulsion, entrapment Chiasmal lesion - tumor, traction Optic tract - prior to split to visual and PLR pathways

Question 34

Abnormal PLRs Efferent lesions

Answer 34

Common in CN III High intracranial pressure, midbrain lesions, orbital fissure syndrome, retrobulbar disease

Question 35

End organ lesions - abnormal PLRS

Answer 35

Junctionopathies High IOP Synechiae Lens lux/sublux Iris atrophy Pharmacological mydriasis (atropine, Tropicamide)

Question 36

Cataracts, SARDS, central blindness

Answer 36

Severe cataracts can be blinding Sudden acquired retinal degeneration syndrome is acutely blinding disorder Central or Cortical vision loss does not necessarily involve the PLR pathways

Question 37

Blindness diseases PLR should be present

Answer 37

PLRs abnormal - suspect concurrent problems Cataracts is a common result from retinal detachment and retinal degeneration SARDs is the most commonly caused by glaucoma/optic neuritis Central blindness common cause is multi focal disease

Question 38

Swinging flashlight test

Answer 38

Detecting difference between two eye in how they respond to light being shone in one eye at a time Marcus Gunn pupil

Question 39

Use of swinging flashlight test

Answer 39

Detecting unilateral or asymmetrical disease of the retina or pre chiasm optic nerve - unilateral retinal detachment - unilateral optic neuritis

Question 40

Horners syndrome

Answer 40

Sympathetic denervation Classical signs - enophthalmos, ptosis, miosis, protrusion of 3rd eye lid Other signs: conjunctival hyperemia, equine sweating, bovine nasal plenum anhydrosis

Question 41

Pathway for Horner’s syndrome

Answer 41

Hypothalamic neurons (1st order) - synapse on sympathetic pre gang neurons (2nd order) - synapse at cranial cervical ganglion on sympathetic post ganglion neurons (3rd order) - enter cranial vault = end at orbital fissure

Question 42

testing for Horner’s syndrome

Answer 42

1 drop of 10% phenylephrine Signs should resolve partially to complete Faster response suggests 3rd order lesion Mydriasis: normal eye & 1st order - 60-90 minutes 2nd order Horners - 20-60 minutes 3rd order - <20 minutes

Question 43

Honers syndrome DDX - pregang disease

Answer 43

Brainstem - neoplasia, inflammatory, vascular trauma Cervical SC - Neoplasia, trauma, FCS, IVDD, luxation T1-3 SC - neoplasia, trauma, FCE, IVDD, luxation Brachial plexus: trauma, avulsion, neoplasia Mediastinal mass, trauma, carotid ligation Neck: aggressive jug stick, accidental carotid stick, bite

Question 44

Horners syndrome DDX - post gang disease

Answer 44

Middle ear - otitis media/intera, polyp, guttural pouch disease, trauma, neoplasia Cavernous sinus - neoplasia, inflammatory disease, vascular disease/aneurysm Retrobulbar - neoplasia, abscess, trauma