Neuro-ophthalmology

Question 1

Understand the reflex pathway of the PLR

Answer 1

Shine light at eye and pupil gets smaller (direct), evaluates the peripheral vision, tests retina and oculomotor nerves

Visual with normal PLR: ok
Visual with absent PLR: efferent problem or pharmacological interference
Blind with normal PLR: something obstructing vision such as cataract
Blind with absent PLR: Problem with retina or optic nerve

Question 2

Recognize the basic tests for vision

Answer 2

Cotton ball test-touch cornea
Menace response- move hand towards eye
PLR-shine light in eye

Question 3

Identify the function and innervation of the extraocular muscles

Answer 3

Rectus mm. 
 Dorsal CN III elevates globe
 Ventral CN III depresses globe 
 Medial CN III turns globe nasally 
 Lateral CN VI turns globe temporally 

Retractor bulbi CN VI retracts globe

Oblique mm.
 Dorsal CN IV intorts globe
 Ventral CNIII extorts globe

Question 4

Know the innervation of the ocular and adnexal structures and recognize the abnormalities that will result with disruption to that innervation

Answer 4

innervation: cranial nerves
abnormalities:
Vestibular disease (central or peripheral)- Lesion of CN VIII
Paralysis of CN VII (Facial nerve) no palpebral response (uni/bilateral)
Strabismus-Paralysis of CN III (Oculomotor nerve)-lat/CN VI (Abducens nerve)-med/ CN IV (Trochlear nerve)-rotated

Question 5

Horner’s syndrome

Answer 5

Loss of sympathetic innervation to the eye due to otitis, chest, or neck disease

Question 6

parasympathetic innervation

Answer 6

ANS; 
Afferent Arm: 
-1- Photoreceptors 
-2- Optic n. (CN II) 
Optic chiasm (50-90% fibers decussate) 
Optic tract 
-3- Pretectal nucleus 
(20% fibers leave) 

Efferent Arm: 
-1- Pre ganglionic fibers 
CN III parasymp. Nucleus (80% fibers cross back) 
-Parasymp. fibers along CN III 
-Ciliary ganglion 
-2- Short ciliary nerve 
-Iris sphincter muscle

Question 7

decussation

Answer 7

cross over of optic nerves in front of pituitary gland

Question 8

optic chiasm

Answer 8

area where optic nerves cross

Question 9

vision testing

Answer 9

Cotton ball test-touch cornea
Menace response- move hand towards eye
PLR-shine light in eye
dazzle reflex
ERG- Electroretinogram recording of the electrical activity of the retina after a bright light flash
Visual evoked potentials (VEP) = recording of the electrical activity of the occipital cortex after a bright light flash

Question 10

menace response

Answer 10

Hand movements in front of the eye -> blink and/or retraction of the globe

• Afferent arm: CN II (Optic n.)
• Efferent arm: CN VII (Facial n.), CN VI (Abducens n.)

Question 11

dazzle reflex

Answer 11

Bright light in front of the eye -> Eyelid closure

• Afferent arm: CN II (Optic n.)
• Efferent arm: CN VII (Facial n.)

Question 12

electroretinography

Answer 12

recording of the electrical activity of the retina after a bright light flash

Question 13

autonomic nervous system

Answer 13

Sympathetic/Parasympathetic

Question 14

sympathetic innervation

Answer 14

ANS; smooth orbital muscle

Question 15

lesion localization

Answer 15

use PLRs to localize lesion based on consensual PLR

Question 16

oculomotor system

Answer 16

Eye position/Eye movement 
CN III (Oculomotor n.) 
 Dorsal (1), ventral (3), medial (2) rectus muscles 
 Inferior oblique muscle (6) 
CN IV (Trochlear n.) 
 Superior oblique muscle (5) – SO4 
CN VI (Abducens n.) 
 Lateral rectus muscle (ns) – LR6 
 Retractor bulbi muscles (4)

Innervation Action 
 Rectus mm.  
Dorsal CN III elevates globe 
Ventral CN III depresses globe 
Medial CN III turns globe nasally 
Lateral CN VI turns globe temporally 
 Retractor bulbi CN VI retracts globe 
 Oblique mm. 
Dorsal CN IV intorts globe 
Ventral CNIII extorts globe

Question 17

Schirmer tear testing

Answer 17

test tear production

Question 18

extraocular muscles

Answer 18

innervated by oculomotor nerve

Question 19

strabismus

Answer 19

lack of parallelism of the visual axes of the eyes

due to oculomotor lesions

Question 20

palpebral reflex

Answer 20

Corneal blink reflex- stimulation of the cornea, closure of lids, retraction of the globe
afferent arm: CN V
efferent arm: CN VI and VII

Question 21

trigeminal somatic sensory system

Answer 21

2 main branches of CN V

Ophthalmic nerve (CN V) 
Supraorbital n. (aka frontal n.): upper eyelid, forehead 
Nasociliary n. (infratrochlear n.): medial canthus, 3rd eyelid: Long & short ciliary nn.:ciliary body, cornea and iris 

Maxillary nerve (CN V): Lateral canthus and lacrimal gland, lower eyelid

Question 22

regional nerve blockade

Answer 22

Used in horses to evaluate eye
Akinesia: motor nerve block (Facial n.)
Sensory Analgesia: sensory nerve block (Frontal n. or Supraorbital n.)

Question 23

consensual PLR

Answer 23

reflex of the other eye to constrict when one eye has bright light shown in it

Question 24

anisocoria

Answer 24

unequal pupil size

Question 25

cranial nerves

Answer 25

Optic nerve (II) – sensory (carries visual info) from retina to 
cortex 
Oculomotor nerve (III) – motor to several extraocular mm. and levator palpebrae superioris m., parasympathetic  hitchhikers 
Trochlear nerve (IV) – motor to superior oblique m. Trigeminal nerve (V) – sensory from eyelids, cornea, lacrimal gland 
Abducens nerve (VI) – motor to lateral rectus m. and retractor bulbi m. 
Facial nerve (VII) – motor to eyelids and other facial mm. 
Vestibulocochlear nerve (VIII) – vestibular component of 
ocular movements

Question 26

optic nerve (CN II)

Answer 26

sensory (carries visual info) from retina to cortex

Question 27

oculomotor nerve (CN III)

Answer 27

motor to several extraocular mm.
and levator palpebrae superioris m., parasympathetic
hitchhikers

Question 28

trigeminal nerve (CN V)

Answer 28

sensory from eyelids, cornea, lacrimal gland

Question 29

facial nerve (CN VII)

Answer 29

Neurology of lacrimation: efferent arm; Auriculopalpebral

branch; eyelid closure