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Neuro-optometry > Lecture 2: Afferent Visual System > Flashcards

Lecture 2: Afferent Visual System Flashcards

1
Q

If the sympathetic system is involved, the anisocoria will become more apparent in the ___

A

Dark, the sphincter that works in the light is intact

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2
Q

Pulfrich’s phenomenon: The pendulum appears to swing closer to the __ eye

A

affected eye, or eye with the neural density filter

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3
Q

What is Savino’s Triad?

A

Pupil/Lids/EOM

  • If patient has a pathological anisocoria worse in bright light and the abnormal pupil is dilated, then you know the parasympathetic system is affected
  • If it is a third nerve palsy causing this issue then you know, based on Savino’s triad that you will also have ptosis and EOM restriction (an eye that is down and out).
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4
Q

What does using a bright (halogen) light do?

A
  • Go slow enough to give the eye time to release
  • Go fast enough to not interrupt the cycle and induce an APD
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5
Q

APD may be found in..? (4)

A
  • Anterior chamber/vitreous hemes (if retinal detachment or significant pathology present causing heme)
  • Optic nerve disorders
  • Optic tract issues
  • Chiasmal issues
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6
Q

APD is never found in..? (4)

A
  • Cataract
  • Refractive errors
  • Lesions posterior to the LGN
  • Non-physiologic visual loss
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7
Q

Describe the parasympathetic pathway: Light reflex input

A
  • Sphincter muscle of the iris - Light reflex input Afferent neurons from retinal ganglion cells to visual cortex
  • Via CN II
    • 2/3 of the way along the optic tract, some (pupillary axons) leave the tract and enter the brachium of the superior colliculus
      • synapse in the pretectal area
      • intercalated neurons form the pretectal complex connect to edinger westphal nuclei, bilaterally
    • The balance of the axons continue to the LGN
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8
Q

Describe the parasympathetic pathway: parasympathetic outflow

A
  • To the sphincter muscle of the iris - parasympathetic outflow
    • Parasympathetic fibers originating from the edinger westphal nucleus
    • Via oculomotor nerve (CN III) to ciliary ganglion and on to sphincter muscle
    • light to one eye allows stimulation of both eyes to constrict
    • One eye does not become dilated due to unilateral eye disease
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9
Q

Describe the parasympathetic pathway stimulation

A
  • Parasympatheticfibers originating at the edinger-westphal nucleus creates the
    • Near synkinesis input
      • originates from peristriate cortex (area 19) of the occipital lobe at the upper end of the calcarine fissure
      • Near synkesis pathway is more ventral than prectal afferent limb of light reflex
        • Convergence, acommodation, miosis
          • 3% of fibers innervate iris sphincter - represents
          • 97% of fibers innervate the ciliary body - represents accommodation
      • More ventral location of the pathway is the anatomical bsis for light-near dissociation
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10
Q

Near reflex fibers travel more ___ than the light reflex fibers

A

Ventrally

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11
Q

The near reflex travels more ventral than the reflex and its origin is in area __ - __

A

19-20

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12
Q

Parasympathetic pathway inhibition: Parasympathetic fibers that originated at the edinger-westphal nucleus is also responsible for..?

A
  • Inhibition of the EW nucleus
    • Inhibits the sphincter
      • Cortical: dilated pupils during seizures
      • Spina-reticular: dilated pupils during arousal, excitement
    • But, sleep, coma: decline of inhibitory influence over EW, pupils ar emiotic
    • Pupils in death: fixed and dialted
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13
Q

Describe the sympathetic pathway first order neuron, second order neuron (pre-ganglionic), and third order neuro (post-ganglionic)

A
  • First order neuron
    • originates in the posterior hypothalamus, travels down through the brainstem, to the ciliospinal center of budge, approximately from C8-T2
  • Second order neuron (pre-ganglionic)
    • leaves spinal cord, enters the paravertebral sympathetic chain, travels through the mediastinum, over the apex of the lung and terminates at the superior cervical ganglion at the base of the skull
  • Third order neuron (post-ganglionic)
    • Pupil fibers ascend the carotid artery to enter the skull, in the cavernous sinus it jumps to the CN VI and then CNV1 and the ophthalmic artery
    • Passes through the superior orbital fissure
      • Fibers on CNV1: muscle of enters the eye dilator via the long posterior ciliary nerves
      • Fibers on ophthalmic artery: travel to muller’s muscle of the lids
    • The sudomotor and vasomotor fibers to the face travel with external carotid and follow the branches of the facial artery
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14
Q

What are the normal pupillary phenomena? (4)

A
  • Physiological Anisocoria
    • 20%
    • Can vary from day to day and switch sides
  • Pupillary Unrest
    • Bilateral, symmetrical, non-rhythmical unrest of less than 1 mm in amplitude
    • Aka hippus
  • Near Synkinesis
    • If normal light pupil responses are present, can assume near-response normal
  • Psycho-sensory reflex
    • sudden noise, startle, pain
    • Helpful when demonstrating horner’s syndrome, the dialted eye dilates even more
      • Turn out the light and make sudden loud sound
    • 2 neural mechanisms occur:
      • Active sympathetic discharge
        • Stimulates iris dilator
      • Inhibition of ocular motor nuclei
        • Relaxation of sphincter
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15
Q

APD

A
  • Extensive vitreous heme/retinal damage can cause APD - RD underlying vitreous heme
  • Cataracts never cause an APD
  • APD requires asymmetry of light transmission/signal conduction - bilateral glaucomatous damage must be asymmetric to produce R-APD
  • APD can occur without VA loss or VF loss - pupillomotor fibers transverse the brachium of the superior colliculus
    • VF fibers continuing to LGN may be spared
  • APD aka marcus-gunn pupil or RAPD
  • optic neuropathy will present with sig APD
  • APD is an afferent defect in CN II conduction pathway
  • Detecting an APD requires only 1 working pupil - if pt has only one reactive pupil (ex. unilateral pharmacologic dilation), you can still check for an APD in that eye of the other eye
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16
Q

What is the best APD testing method?

A
  • Magnifier assisted swinging flashlight test
    • Transilluminator and 20D lens
    • Hold 20D over eye being tested
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17
Q

How do we grade APD?

A
  • Using a neutral density filter to measure APD
    • Hold the filter over the unaffected eye
    • Increase log unit until APD no longer seen
    • 0.3, 0.6, 0.9 and 1.2 log units
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18
Q

Describe APD by reverse

A
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19
Q

Pathological Anisocoria: anisocoria ___ in the direction of the paretic muscle

  • Spinchinter is affected, worse anisocoria in __ __
    • __ system is involved
      • Adie’s Tonic pupil - Mydriasis
  • Dilator affected, worse anisocoria in __ __
    • __ system involved
      • Horner’s syndrome - Miosis
A
  • Increases
  • Bright light
  • Parasympathetic
  • Dim light
  • Sympathetic
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20
Q

What are some differential diagnosis for an abnormal pupil that is dilated (parasympathetic system)?

A
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21
Q

What are some differentials if you see the abnormal pupil is constricted? (sympathetic system)

A
  • Iritis - pain
  • Horner’s syndrome - mild ptosis
  • Argyll- Robertson pupil - usu bilateral, can have anisocoria
  • Long standing Adie’s pupil - initially dilated pupil may constrict over time
  • Miotic drops
  • “Green cap” medication
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22
Q

What can cause Adie’s (Tonic pupil)?

A
  • Idiopathic, benign cause of internal ophthalmoplegia
    • Lesionmight be in the ciliary ganglion or short posterior ciliary nerves
  • May be due to immune reaction, often seen after chickenpox in children
  • Early syphilis
  • Parvovirus 19
  • Neurological lyme disease
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23
Q

Descibe Adie’s syndrome (Aka holmes-Adie’s syndrome)

A
  • Pupil anomaly plus absent deep tendon reflexes and decreased vibratory sense
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24
Q

Adie’s tonic pupil unilateral or bilateral?

A

80% unilateral, tend to become bilateral

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25
Q

Adie’s are typicall found in (M/F) between the age of __ - __

A
  • Female predilection
  • Young adults 20-40 yoa
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26
Q

Describe what you could see in a patient with Adie’s (Tonic) pupil

A
  • The affected pupil is dialted with poor/absent reaction to light
  • Slow constriction after prolonged near effort, and slow re-dilation after near effort (tonic) ‘
  • Initial accommodative paresis resolves after several months
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27
Q

How would you test for Adie’s pupil?

A
  • If the iris has been deprived of nerve input for a few (5-7) days, it becomes super-sensitive to dilute concentrations of cholinergic or adrenergic drops (denervated)
  • Weak pilocarpine (0.125%) instilled in both eyes
    • Affected pupil constricts more than the normal pupil
    • Segmental denervation of the iris sphincter visible
  • Light-near dissociation occurs due to regeneration of the nerves to the ciliary muscle after about 2 months
    • Sign of chornic Adie’s pupil
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28
Q

Describe Horner’s Syndrome

A
  • Greater anisocoria in dim illumination
    • ​Transient findings
      • Might see increase in pseudo-accommodation in older patients in eye with miosis
      • IOP might be lower
      • Hemi-facial flush: dilated conjunctival/facial vessels (Harlequinsign)
        • Seen on affected side when crying/nursing
        • Atropine on affected side reduces flush
    • Sympathetic system determines: “curl and color”
      • Iris hterochromia in congenital cases: sympathetic input needed for pigment disposition
      • Congenital horner’s may make child’s hair straight on the affected side
        • Sympathetic input needed for curly hair
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29
Q

How would you test the preganglionic lesion and post ganglion lesion for horner’s syndrome?

A

Spoon test

  • Preganglionic lesion
    • Spoon will catch on skin - no sweat
  • Postganglionic lesion
    • Spoon will glide - sweat present
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30
Q

What can cause acquired horner’s?

A
  • Beauty shop dolichoectasia
  • Vertebral artery dissection
    • From cradling a phone
    • Heavy backpacks in children
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31
Q

Horner’s syndrome in children should be evaluated for ___

A
  • Neuroblastoma
  • Most common tumor cause of pediatric horner’s syndrome
  • 5% arise in the cervial sympathetic chain
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32
Q

List the most likely etiologies for Horner’s syndrome

  • First order neuron
  • Second order neuron
  • Third order neuron
A
  • First order neuron
    • Stroke, MS
      • MS have been documented with alternating horner’s syndrome
    • Rare: osteoarthritis with bony spurs
  • Second order neuron
    • ​Tumor, lung carcinoma, metastasis thyroid adenoma
      • Pancoast’s tumor (NSC) may be associated with pain in arm/scapula
    • Children: neuroblastoma, lymphoma, metastasis
  • Third order neuron
    • Headache syndromes
      • Cluster, migraine, Raeder’s paratrigeminal syndrome
    • Internal carotid dissection
    • Herpes zoster virus
    • Otitis media
    • Tolosa-Hun syndrome
    • Neck trauma
    • Tumor
    • Inflammation
    • Pituitary adenoma
    • MOST LIKELY: ipsilateral horner’s plus 6th nerve palsy
      • aka parkinson’s syndrome
      • Lesion most likely in cavernous sinus
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33
Q

How would you test for horner’s syndrome?

A
  • 3 neuron arc of sympathetic system
    • 1st order neuron transmitter: acetylcholine
    • 2nd order neuron transmitter: acetylcholine
    • 3rd order neuron transmitter: nor-epinephrine
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34
Q

How does testing with cocaine work with horner’s syndrome?

A
  • Cocaine is a mydriatic and dilates normal pupils
    • ​Instill one drop 4-10% cocaine in each eye
    • Solution of 4% cocaine blocks the reuptake of nor-epinephrine
      • Sympathomimetic effect of cocaine
        • Blocks norepinephrine receptors at the myoneural junction, thereby prolonging the action of norepinephrine in the normal eye
        • Pupils dilate
  • In an interrupted sympathetic pathway, there is no nor-epinephrine released at the 3rd order neuron
    • The unaffected pupil dilates while the miotic pupil remains small and the anisocoria increases
    • cocaine does NOT dilate horner’s pupil
    • makes the anisocoria even more evident
      • Cocaine stings
      • Pt should stay awake
    • Cocaine test only confirms horner’s syndrome and does not differentiate which neuron arc is affected
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35
Q

IF the cocaine test is positive, what can you do next?

A
  • IF the cocaine test is positive (increase anisocoria)
    • Instill 2.5% phenylephrine
      • Now easily dilates the horner’s eye!
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36
Q

When should you use apraclonidine instead of cocaine for horner’s syndrome?

A
  • 0.5% apraclonidine (instead of cocaine)
    • Can use if horner’s syndrome is present > 1 week
    • Sympathetic alpha-agonist
    • Will make the horner’s eye dilate
    • Creates anisocoria in the other direction
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37
Q

What is paredrine (1% Hydroxy-Amphetamine) used for?

A
  • Used to determine if the lesion is preganglionic or postganglionic (Horner’s)
    • Instill one drop in each eye
    • Paredrine creates a sympathomimetic effect
      • Causes the release of nor-epinephrine from the nerve endings at the myoneural junction
    • Paredrine only works at the 3rd order neuron, there is no nor-epi at 1st and 2nd order
      • Paredrine dilates the normal pupil
      • Paredrine dilates the affected pupil if either the 1st and 2nd order neuron is affected, and only if the 3rd order neuron is intact
      • If the 3rd order neuron is affected, the dilation response will be poor
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38
Q

How does paredrine (Hydroxyamphetamine) work? What if the lesion is in pre-ganglionic? What if the lesion is post-ganglionic?

A
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39
Q

How would you perform a horner’s syndrome work up?

A
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40
Q

Describe what an argyll-robertson pupil looks like?

A
  • Small, irregular pupils
  • Light - near dissociation
  • Usually bilateral
  • May be asymmetric
41
Q

What causes argyll-robertson pupil and how would you perform a work-up for this patient?

A
  • Etiology is usu tertiary syphillis
    • Diabetes, chronic alcoholism
  • Work-up
    • Look for findings of syphilis with SL
      • Interstitial keratitis (hazy looking eye)
    • Chorio-retinitis
    • Papillitis
    • Uveitis
42
Q

What are some lab testings for argyll-robertson pupils?

A
  • Fluorescent treponemal antiboid absorbent (FTA-ABS)
  • Micro-hemagglutination Treponema Pallidum (MHA-TP)
  • Rapid plasma reagin (RPR)
  • Venereal disease Research Laboratories (VDRL
43
Q

What are 2 types of pupils in coma?

A
  • Hutinchinson’s
  • Miosis
44
Q

Describe Hutchinson’s Pupil?

A
  • Describes a comatose patient with unilaterally dilated, poorly reactive pupil
    • Due to ipsilateral expanding, intracranial, supratenorial mass
    • Tumor, subdural hematoma
  • Downard displacement of hippocampal gyrus and uncal herniation with CN III entrapment
45
Q

Describe Miosis

A
  • During early stages of coma: cortical inhibitory input to EW diminished and pupils are small and reactive to light
  • Remember that the pupils may be constricted due to morphine overdose!
46
Q

For color vision how would you identify congenital loss vs neurological loss?

A
47
Q

Describe amsler Grid

A
  • Very sensitive to central VF loss
  • Use red-on-black squre
    • More sensitive for more subtle optic neuropathies
    • 1 block = 1 degree
    • Total of 10 degrees either side and above fixation at 30cm (14 inches)
48
Q

Describe Contrast Sensitiviy testing, what is the gold standard?

A
  • Measure the ability to differentiate between light & dark
  • VA of 20/20 may have a potential hidden loss in contrast sensitivity
  • Contrast sensitivity measures visual function from low to high spatial frequencies
  • Especially important for patients with optic neuritis
    • Optic neuritis = inflammation of the optic nerve
  • Peli-Robson is the gold standard - can use M&S software
  • Considerations
    • Day of testing (personal variables)
    • Test distance
    • Test illumination
    • Font/type size and spacing
49
Q

What does the brightness comparison test for?

A
  • Check for unilateral optic neuropathy
    • Shine a white light into pt’s eye
    • Compare brightness
    • Estimate percentage difference
50
Q

What does the photostress test test for?

A
  • Differentiates retinal disease from optic neuropathy
    • Independent of neural pathway
  • This test has measurable outcome
    • Photostress test recovery time
  • Procedure
    • Determine the best VA in each eye
    • Look directly into the light for 10 sec 2-3cm from eye
    • Record the time taken to return to best VA
      • Normal is less than 30 seconds
    • less than 10 seconds is normal
51
Q

What are you looking for when observing the nerve with an ophthalmoscopy?

A
  • Stereo evaluation with a 60, 78, or 90D lens
    • Look for
      • Swelling of the papilla (unilateral/bilateral elevation)
        • Signs of past swelling: Patton’s lines
      • Hemorrhages or dilated nerve vessels
        • Drance/splinter hemes or telangiectasia of the nerve
        • Collateral/shunt vessels (tumor/CRVO)
        • Nevoascularization of the disc (DM)
      • Congestion of the peri-papillary vessels
        • Nerve fiber layer swelling is pathognomonic of a swollen disc
      • Pallor, sectoral pallor
      • C/D ratio
      • Spontaneous venous pulse (SVP)
      • Peri-papillary area
        • Peri-papillary atrophy
52
Q
A
53
Q
A

Optic neuritis

54
Q
A

Anterior arteritic ischemia neuropathy

55
Q
A
56
Q
A

Post-meningitis resolution of optic nerve swelling and resultant optocillliary shunt vessels (aka collaterals)

57
Q
A

Neovascularizaiton of the optic disc

58
Q
A
  • Optic nerve pallor
59
Q
A
  • Bilateral pallor.. chronicity?
60
Q

Describe VF importance of neurological findings?

A
  • Poor man’s MRI
  • Screen with very careful confrontation testing/FDT
  • Always follow up abnormal findings with formal VF test
  • Allunexplained complaints of HA qualify for full formal VF test (NOT screening!)
  • Neuro 120pt is available as testing strategy on humphrey
    • Not a threshold test (long test)
  • Normally just run 24-2 or 30-2 (NOT SITA-FAST)
61
Q

List some neuroimaging

A
  • B-scan ocular ultrasound
    • EOM
    • Ocular tumors
    • Orbital tumors
    • Optic nerve
      • Papilledema
      • Optic disc drusen
  • MRI and CT
  • MR Angiogram
62
Q
A

Disc drusen & Drance hemes

63
Q
A

Buried drusen of the optic nerve

64
Q

How does a B-scan ultrasound work?

A
65
Q

Describe the wave of a B scan ocular ultrasound

A
  • Frequency of the sound wave is
    • The number of oscillations per second
    • Inaudible to human ear
  • The higher the frequency, the shorter the wavelength
    • Shorter wavelength (gain) = improved resolution!
  • The medium through which it travels determines the velocity
    • Slower through aqueous and vitreous, faster through lens and cornea
  • When the wave goes from one density to another, part of the sound is reflected, aka “echo”
    • The greater the density difference at the interface, the stronger the echo
66
Q

What are the two types of ultrasound scans?

A
  • A scan
  • B scan
67
Q

Describe what information an A-scan provides

A
  • Amplitude modulation scan
  • Gives one-dimensional information
  • Gives measurements such as axial length or elevation of a mass
68
Q
A

Melanoma

69
Q
A

Choroidal melanoma

70
Q
A

Thyroid eye disease

71
Q

Papilledema

A

Crescent sign in papilledema: subarachnoid fluid accumulation around optic nerve

72
Q

Describe the basic principles of a CT-scan

A
  • Beam of X rays with detectors and computer algorithm that reconstructs image
  • Blunting/attenuation of the ray:
    • Dense tissue blocks lots of x-rays
    • Grey matter blocks some
    • Fluid blocks less
73
Q

Is this image CT or MRI?

A
  • CT Scan
  • Dense tissue blocks more x-rays
  • Grey matter blocks some
  • Fluid blocks less
74
Q

What are the basic principles of MRI?

A
  • Protons oscillate in a magnetic field
  • 2 steps:
    • The protons absorb energy
    • The proteins release energy
  • This return to original state is the MRI signal
  • This process can occur in 2 directions
    • Relaxation parallel to the magnetic field takes time (T1)
    • Relaxation perpendicular to the magnetic field takes time (T2)
75
Q

Describe the difference between MRI T1, T2, and CT

A
76
Q

Which one is T1, T2, and Flair?

A
77
Q

Describe T1 and T2 weight sequence/image

A
78
Q

Describe abnormal findings in T1, T2, and CT

A
79
Q

What slice orientation is this?

A
80
Q

What slice orientation is this?

A
81
Q

What slice orientation is this?

A
82
Q

What type of scan is this and what are the slice orientation of each?

A
83
Q
A
84
Q
A
  • MR angiograms (Nontomographic)
  • Single projection with contrast X-ray angiogram
85
Q
A
86
Q

CT or MRI? Orientation?

A
  • Transverse (left) & CT
  • Coronal (right) & MRI
87
Q

What is SPECT/PET?

A
88
Q
A
89
Q
A
  • RNFL elevation
  • Papilledma
90
Q

What are the RNFL thinning potential causes (OCT)? (11)

A
  • Glaucoma
  • Vascular, vitamins
  • Inflammatory, infectious
  • Autoimmine, allergic
  • Metabolic, mass lesions
  • Inherited, idiopathic
  • Neurodegenerative
  • Endocrine, environemtnal
  • Senility, stress
91
Q
A
  • OCT ganglion cell complex
92
Q

List 3 evoked potentials

A
93
Q
A
  • CT
  • Transverse-axial
  • Tumor
94
Q
A
  • CT
  • Transaxial cut
95
Q
A
  • Bright = bleed
  • CT
96
Q
A
  • MRI, saggittal, tumor (blood)
97
Q
A

MS

98
Q

content of lesion? Scan?

A
99
Q

Contents?

A
  • MRI, Sagittal,
  • Tumor, pseudoxanthoma; personality changes

Neuro-optometry (3 decks)

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