This document summarizes a lecture on demystifying the neuro-ophthalmologic exam. It discusses the anatomy and pathways involved in pupillary control, visual pathways, ocular movements, eyelid innervation, and lacrimation. It provides outlines of topics covered, including the pupillary light reflex pathway, ocular movement control, and tests used to evaluate these systems like the menace response, dazzle reflex, vestibulo-ocular reflex, and Schirmer tear test.

1. SATURDAY NOVEMBER 11, 2017
TODD M. BISHOP, DVM, DACVIM (N)
NEUROLOGY & NEUROSURGERY
UPSTATE VETERINARY SPECIALTIES
DEMYSTIFYING THE NEURO-
OPHTHALMOLOGIC EXAM

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 Pupillary control
 Visual pathways
 Ocular movements
 Eyelid innervation
 Lacrimation
 Anatomic localization
 Case examples
LECTURE OUTLINE
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 Like every reflex there is …
 Sensory (Afferent) component
 Motor (Efferent) component
THE PLR
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AFFERENT ARM OF PLR
 R= retina
 II= optic nerve
 OC= optic chiasm
 OT= optic tract
 PTN= pretectal nucleus
 LGN= lateral geniculate nucleus
 PSN= parasympathetic nucleus of CN
III
 III= oculomotor nerve
 CG= ciliary ganglion
 SCN= short ciliary nerve
R
II
OC
OT
PTNLGN
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CHIASMAL DECUSSATION
Primates=50%
Feline=65%
Canine=75%
Equine, bovine,
porcine=80-90%
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FATE OF THE POST-CHIASMAL OPTIC TRACT
20% of fibers synapse in
PTN to complete PLR
80% of fibers synapse in
LGN bound for the visual
cortex
20%80%
PTNLGN
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EFFERENT ARM OF PLR
 R= retina
 II= optic nerve
 OC= optic chiasm
 OT= optic tract
 LGN= lateral geniculate nucleus
 PTN= pretectal nucleus
 PSN= parasympathetic
nucleus of CN III
 III= oculomotor nerve
 CG= ciliary ganglion
 SCN= short ciliary nerve
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PTN
PSN
III
CG
SCN

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GEE WIZ ….
Dogs have 5-8 SCNs
Cats have 2 SCNs:
 Nasal and malar branches
 Only carry PSN fibers
 “D-shaped” pupil
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 Pupillary constriction
 Parasympathetically mediated (Ach)
 Pupillary dilation
 Sympathetically mediated (norEpi)
IRIDIAL MUSCULATURE
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SYMPATHETIC
INNERVATION
#1
#2#3
Very uncommon!
#4
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HORNER SYNDROME
Miosis
Ptosis
Enophthalmus
Nictitans protrusion
Episcleral injection
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 2.5% phenylephrine
 Pupil dilation
 resolution of ptosis
 Retraction of nictitans
 5-8 minutes
 Lesion in 2nd LMN
0.001% Epinephrine
 Pupillary dilation
 20 minutes if 2nd LMN
affected
 38-40 minutes if 1st LMN
affected
PHARMACOLOGIC TESTING: SYMPATHETIC
DISTURBANCES
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0.5% physostigmine
 Indirect PNS
 UMN lesion → rapid
constriction
 LMN lesion → no
constriction
 Normal eye → constriction
w/ in 40-60 mins.
2% pilocarpine
 Direct PNS
 Rapid pupil constriction
with either UMN or LMN
lesion
 Normal eye constricts w/
in 20 mins.
 A rule out for iris atrophy
(would not constrict)
PHARMACOLOGIC TESTING: PARASYMPATHETIC
DISTURBANCES
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 Easy to see mydriasis in bright sunlight (ie. A cat in a window
sill).
 Easy(ish) to see miosis in the dark.
 But what about asymmetric pupils in ambient room light?
 Which pupil is affected?
 Is one pupil too small or is the other too big?
ANISOCORIA
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 If you think a pupil is too big, put a bright light into that eye and
observe for complete constriction.
 If you think a pupil is too small, bring the patient into the dark
and observe for complete dilation.
KEEP IT SIMPLE …
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USE A BRIGHT LIGHT!
Non-

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Mydriasis
 Oculomotor
nucleus/nerve lesion
 Iris atrophy
 Glaucoma
 Posterior synechia
 Pharmacological blockade
Miosis
 Horner syndrome
 Supranuclear inhibition
 Uveitis
 Keratitis
 Posterior synechia
ANISOCORIA
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 Is there a direct response to bright light (directed into the
temporal retina)
 Reaction? Complete? (sluggish?)
 Is there a consensual (indirect) response when light in shown in
the fellow eye?
WHEN EVALUATING THE PLR
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DYNAMIC CONTRACTION
ANISOCORIA
anisocoria (direct PLR >
indirect PLR)
Occurs in non-primates
due to unequal
decussation of fibers
75%25%
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 “positive test” occurs when illuminated eye dilates rather than
constricts
 “Marcus-Gunn pupil”
 Unilateral retinal or optic nerve lesion
SWINGING FLASHLIGHT TEST
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PARADOXICAL PUPIL
Central chiasm lesion
Symmetric mydriasis
Direct and indirect PLR
present
Indirect response >
direct response !!!
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CEREBELLAR AFFECTS ON PUPILS
 Fastigial lesion
 Contralateral mydriasis
 Ipsilateral nictitans protrusion
 Interpositus lesion
 Ipsilateral mydriasis
 Contralateral nictitans
protrusion
F
L
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I

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LET’S REVIEW
Afferent Arm
 PLR abnormal
 Vision affected
Efferent Arm
 PLR abnormal
 Vision normal
Cortical lesion (after OT
splits)
 PLR normal
 Vision affected
R
II
OC
OT
PTNLGN
PSN
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CONSCIOUS
VISUAL PERCEPTION
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 Menace response (12 weeks)
 Dazzle reflex
 Cotton ball drop
 Visual placing reaction
 Obstacle course
VISUAL ASSESSMENT
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 Response NOT reflex
 Closure of palpebral fissure +/- globe retraction, head turn
 Puppies develops between 10-12 weeks of age
 Cortically mediated response
 Requires that the entire visual pathway be intact
 CereBELLAR lesion may cause IPSILATERAL menace
deficits WITHOUT vision loss!
MENACE RESPONSE
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MENACE RESPONSE
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 a subcortically mediated “brainstem” REFELX
 Palpebral fissure closes in response to bright stimulus
 Lids may open then close
 Ipsilateral response > contralateral response
DAZZLE REFLEX
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DAZZLE REFLEX
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OCULAR MOVEMENT CONTROL
 CN III (Oculomotor)
 Medial rectus (adduction)
 Dorsal rectus (elevation)
 Ventral rectus (depression)
 Ventral oblique (extortion)
 CN IV (Trochlear)
 Dorsal oblique (intortion)
 CN VI (Abducens)
 Lateral rectus (abduction)
 Retractor bulbi (retraction)
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 Vestibulo-ocular reflex (VOR)
 a.k.a. Doll’s eye or oculocephalic reflex
 Corneal reflex (V-VI/VII)
 Resting or positional strabismus
TESTING OCULAR MOVEMENTS
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VESTIBULO-OCULAR REFLEX (VOR)
VIII→MLF →III,IV,VI
Move head horizontal to
RIGHT
 Smooth pursuit LEFT
 Saccade beat RIGHT
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CORNEAL REFLEX (V-VI/VII)
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RESTING STRABISMUS
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 Afferent innervation
 Medial canthus (V-ophthalmic)
 Lateral canthus (V-maxillary)
 Efferent innervation
 Levator palpebrae superioris (III)
 Orbicularis oculi (VII)
 Muller’s muscles (SNS in Voph)
* lack of input from any of these → PTOSIS
EYELID INNERVATION
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 Palpebral reflex (Voph/max → VII)
 Corneal reflex (Voph → VII)
 Menace response (II → VII)
 Dazzle reflex (II → VII)
TESTING EYELID INNERVATION
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LACRIMATION
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VII nucleus (PSN)
VII
major pertosal n.
n. of pterygoid canal
pterygopalatine ganglion
Lacrimal n. (Voph) Zygomaticotemporal n. (Vmax)
lacrimal gland

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VII → V
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 Schirmer Tear Test (STT)
 Tests for neurogenic KCS
 Also look for xeromycteria (zē′rō-mik-tē′rē-ă)
 Dry nose on the ipsilateral side
TESTING LACRIMATION SYSTEM
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 Neuroparalytic keratitis
 Exposure keratitis due to facial (VII) paralysis
 Uncommon complication in dogs and cats due to presence of the
nictitans
 Neurotrophic keratitis
 Trigeminal (V) nerve provides trophic factors necessary for corneal health
 denervation → epithelial degeneration and stromal edema
 Progressing to desiccation, neovascularization, opacification, ulceration
and even perforation
 Some eyes may require enucleation
NEUROGENIC KERATITIS
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 Generally non-responsive to topical Cyclosporine and Tacrolimus
 Oral pilocarpine therapy may be required:
 Directly stimulates denervated gland
 Use 2% pilocarpine eye drops as follows:
 2 drops per 20 lbs body wt. BID w/ food
 Inc. dose by 1-2 drops per week until toxicity (V/D) occurs, then back off one step
 May require lifelong therapy
TREATING NEUROTROPHIC KCS
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 Ask yourself these questions …
 Is the pet BLIND (no menace)?
 If so which eye?
 Is there ANISOCORIA?
 If so, which pupil is too big or too small?
 Are the PLRs intact?
 If so are they intact directly and consensually?
ANATOMIC DIAGNOSIS (ADX)
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LET’S REVIEW AGAIN!
 Afferent Arm
 PLR abnormal
 Vision affected
 Efferent Arm
 PLR abnormal
 Vision normal
 Cortical lesion (after OT
splits)
 PLR normal
 Vision affected
R
II
OC
OT
PT
N
LGN
PSN
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UNILATERAL LEFT RETINAL LESION
 BLIND?
 Yes, ipsilateral (OS).
 ANISOCORIA?
 Yes, ipsilateral mydriasis (OS)
 PLRs?
 Light in OS → no constriction OU
 Light in OD → constriction OU
* WARNING: PLRs may persist with
advanced retinal disease!
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UNILATERAL LEFT OPTIC NERVE LESION
 Same findings as unilateral
retinal lesion
 Positive swinging flashlight
test
 ADx: retina or optic nerve
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 BLIND?
 Yes, bilaterally.
 ANISOCORIA?
 No, but mydriasis OU.
 PLRs?
 Light in OS → decreased to no
response OU
 Light in OD → decreased to no
response OU
 Paradoxical pupil?
 ADx: bilateral retina/optic nerve or
optic chiasm
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OPTIC CHIASM LESION

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 BLIND?
 Yes, contralateral (OS)
 ANISOCORIA?
 Yes, but subtle mydriasis (OS)
 PLRs?
 Light in OS both constrict but OS
incomplete
 Light in OD both constrict but OS
incomplete
 Swinging flashlight test is
Negative
 ADx: similar to retina/optic
nerve but anisocoria and PLRs
less affected
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UNILATERAL RIGHT OPTIC TRACT LESION

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BLIND?
 No, sighted OU
ANISOCORIA?
 Yes, mydriasis (OS)
PLRs?
 Light in OS, constriction OD
 Light in OD, constriction OD
ADx: efferent ONLY on left
as vision not affected
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OCULAR MOTOR NERVE (NUCLEUS) LESION ON LEFT

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 BLIND?
 Yes, contralateral (OS)
 ANISOCORIA?
 No
 PLRs?
 Light in OS, constriction complete
and symmetric OU
 Light in OD, constriction complete
and symmetric OU
 ADx: lesion must be caudal to
where OT splits to PTN and LGN
on the right side
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UNILATERAL RIGHT CORTICAL LESION

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BILATERAL CORTICAL LESIONS
 BLIND?
 Yes, bilaterally (OU)
 ANISOCORIA?
 No
 PLRs?
 Normal OU
 ADx: bilateral occipital lobe
 DDx: hypoxia, thiamine,
lead, storage diseases
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 Sig: 3-yr MI Doberman pinscher
 CC: dilated left pupil
 Hx: duration of 6 days
 Neurologic exam:
 Normal menace OU
 Left pupil widely dilated in room light
 Light OS – only OD constricts
 Light OD – only OD constricts
 No strabismus; slight ptosis & dec. adduction OS
CASE STUDY #1
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CASE STUDY #1
 BLIND?
 No, sighted OU
 ANISOCORIA?
 Yes, mydriasis (OS)
 PLRs?
 Only OD responds
 Bonus Info:
 Ptosis OS (Lev. Palp. Sup.)
 ↓ adduction OS (Med. Rectus)
http://www.omconcept.fr
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 Anatomic Diagnosis?
 left oculomotor n (III) nucleus or
nerve
 Definitive Diagnosis?
 Germ Cell Tumor
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CASE STUDY #1

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 Sig: 3-yr FI miniature poodle
 CC: seizures, abnormal behavior
 Hx: 5 generalized seizures over the past week; 3 day
progressive lethargy w/ circling and head pressing
 Neurologic exam:
 Profound lethargy, tends to circle to right w/ normal gait; slow
postural reactions on left side
 No menace OU, w/ widely dilated pupils OU
 Light OS- no response OU
 Light OD- initially no response OU, then when light directly
medially toward nasal retina, both pupils constrict
CASE STUDY #2
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CASE STUDY #2
BLIND?
 Yes, bilaterally
ANISOCORIA?
 No, but mydriasis OU
PLRs?
 Only in nasal retina OD
www.pamperedpuppy.com
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CASE STUDY #2
Anatomic Diagnosis?
 incomplete optic chiasm vs.
bilateral optic tract
Definitive Diagnosis?
 Pituitary Macroadenoma
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 Sig: 8 yr. MI MIXB
 CC: acting blind
 Hx: Sudden onset of bumping into objects
 Neurologic exam:
 No menace OU
 Both pupils moderately dilated in room light
 Light OS – pupils constrict OU
 Light OD – pupils constrict OU
 Remainder of neuro exam is WNL
CASE STUDY #3
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CASE STUDY #3
BLIND?
 Yes, bilaterally
ANISOCORIA?
 No, but mydriasis OU
PLRs?
 Intact OU
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CASE STUDY #3
 Anatomic Diagnosis?
 bilateral retina/optic nerve >
optic chiasm
 Differential Diagnosis?
 OPTIC NEURITIS
 Pituitary Tumor
 SARDS
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 Sig: 3 yr. MI Collie
 CC: seizures
 Hx: generalized seizures monthly for past 8 months
 Neurologic exam:
 No menace OS
 Both pupils normal size/symmetry in room light
 Light OS – no response OU
 Light OD – pupils constrict OU
 As you swing from OD to OS, OS dilates to original size. Cover OD w/
hand and OS dilates widely.
CASE STUDY #4
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CASE STUDY #4
 BLIND?
 Yes, blind OS
 ANISOCORIA?
 OS widely dilated in dark
 PLRs?
 Only when light in OD
 Positive swinging flashlight test
(OS dilates in bright light) http://www.aht.org.uk/images/retina6.jpg
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CASE STUDY #4
 Anatomic Diagnosis?
 left retina or optic nerve
 Definitive Diagnosis?
 Coloboma (Collie Eye Anomaly-
CEA)
http://www.aht.org.uk/images/retina6.jpg
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 Sig: 10 yr. FS Boxer
 CC: depressed, circling
 Hx: 1 month progressive Hx of depression, failure to recognize
owner and circling to left
 Neurologic exam:
 Depressed
 Circling LEFT
 RIGHT-sided postural reaction deficits
 No menace OD
 Normal pupil size, symmetry and reaction to light
CASE STUDY #5
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM

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CASE STUDY #5
BLIND?
 Yes, blind OD
ANISOCORIA?
 No, symmetric pupils
PLRs?
 Normal OU www.kingdomofpets.com
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM

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CASE STUDY #5
Anatomic Diagnosis?
 Left prosencephalon (forebrain)
Definitive Diagnosis?
 Glial tumor
www.kingdomofpets.com
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 Sig: 10 yr. MC MIXB
 CC: exophthalmia OS
 Hx: 1 month progressive history of sneezing, intermittent
epistaxis (left nares) and pain on opening jaw
 Neurologic exam:
 No menace OS
 widely dilated pupil OS
 Light OS- no response OU
 Light OD- only OD constricts
 OS difficult to retropulse
CASE STUDY #6
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM

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CASE STUDY #6
 BLIND?
 Yes, blind OS
 ANISOCORIA?
 Yes, mydriasis OS
 PLRs?
 OD constricts but only
directly
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM

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CASE STUDY #6
Anatomic Diagnosis?
 left optic (II) and
oculomotor (III) nerves
Definitive Diagnosis?
 Chondrosarcoma in the LEFT
retrobulbar space
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM

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 First, ask yourself …
 BLIND?
 ANISOCORIA?
 PLRs?
 What is affected?
 PLR and vision?
 PLR only?
 Vision only?
IN SUMMARY …
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM

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 Afferent Arm
 PLR abnormal
 Vision affected
 Efferent Arm
 PLR abnormal
 Vision normal
 Cortical lesion (after OT
splits)
 PLR normal
 Vision affected
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM
ONE LAST TIME …
R
II
OC
OT
PT
N
LGN
PSN

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 Michael Davidson, DVM, DACVO for providing an outline and
some slides for this talk
 Alexander De Lahunta, DVM, Ph.D for his spiritual guidance
 Amanda Blackburn, DVM, DACVIM for assistance with image
acquisition
A SPECIAL THANKS TO …
11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM